Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento y parámetros de calidad de la leche en las cabras canarias
Abstract
Programa de Doctorado: Sanidad Animal
Full text
Alexandr Torres Krupij Octubre 2013 Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias
Anexo II UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA Departamento: Instituto Universitario de Sanidad Animal y Seguridad Alimentaria Programa de Doctorado: Sanidad Animal Título de la Tesis “EFECTO DE LA FRECUENCIA DE ORDEÑO SOBRE LA PRODUCCIÓN, FRACCIONAMIENTO LECHERO Y PARÁMETROS DE CALIDAD DE LA LECHE EN LAS CABRAS CANARIAS” Tesis Doctoral presentada por D. Alexandr Torres Krupij Dirigida por los Dres. D. Anastasio Argüello Henríquez y D. Juan Capote Álvarez Las Palmas de Gran Canaria, a 15 de julio de 2013 Anastasio Argüello Henríquez El Doctorando, El Director, Alexandr Torres Krupij El Director, Juan Capote Álvarez
ANASTASIO ARGÜELLO HENRÍQUEZ, PROFESOR TITULAR DE UNIVERSIDAD EN EL DEPARTAMENTO DE PATOLOGÍA ANIMAL, PRODUCCIÓN ANIMAL, BROMATOLOGÍA Y TECNOLOGÍA DE LOS ALIMENTOS DE LA FACULTAD DE VETERINARIA DE LA UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA INFORMA: Que Alexandr Torres Krupij, Ingeniero Químico, ha realizado bajo mi dirección y asesoramiento el presente trabajo titulado “EFECTO DE LA FRECUENCIA DE ORDEÑO SOBRE LA PRODUCCIÓN, FRACCIONAMIENTO LECHERO Y PARÁMETROS DE CALIDAD DE LA LECHE EN LAS CABRAS CANARIAS” considerando que reúne las condiciones y calidad científica para optar al grado de Doctor en Veterinaria. Las Palmas de Gran Canaria, julio 2013 Fdo. Anastasio Argüello Henríquez
AGRADECIMIENTOS Ni en estas líneas ni en un libro entero puedo plasmar mi gratitud a las personas e instituciones que han hecho posible la realización de esta tesis. Soy de los que prefieren mostrar cotidianamente mi agradecimiento de muchas formas, sin necesidad de esperar al final para enumerar una a una las personas que han sido importantes en este trabajo. Sin embargo, me gustaría mencionar: • AlINIAporlaoportunidaddefinanciarmidoctorado,sinlocual,hubiese sido prácticamente imposible continuar con la formación. • MuchasgraciasalequipodetrabajodelDepartamentodeProducción AnimaldelaULPGCyalaUnidaddeProducciónAnimal,PastosyForrajes del ICIA. A los “jefes” de dichos grupos, por mostrarme las directrices a seguir y contribuir a lograr los objetivos pautados. A mis compañeros de laboratorio (estudiantes y personal técnico) por brindarme su amistad yayudadesinteresada.Porcompartirtantosmomentosagradables.Me siento orgulloso de haber pertenecido a estos grupos. • EspecialmentegraciasalpersonaldelaEscueladeCapacitaciónAgraria de Arucas, por hacer que mi estancia fuese tan entrañable, fueron como una familia para mí y nunca los olvidaré. • Porúltimo,menciónespecialaesaspersonas,queaunquenopertenezcan a este mundo de cabras, experimentos-resultados y papers, me animaron en su momento a empezar un doctorado, a continuar cuando las fuerzas disminuían, y a darme el empujón final con alegría y esperanza. Graciasdecorazón.
Textos: Instituto Canario de Investigaciones Agrarias. Finca“Isamar”,Ctra.deElBoqueróns/n,ValleGuerra.LaLaguna.Tenerife.38270. Facultad de Veterinaria de la Universidad de Las Palmas de Gran Canaria. CampusUniversitariodeArucas.Arucas.35416. Diseño y cuidado editorial MónicaPedrós Fotografía de portada Fermín Correa
INDICE INTRODUCCIÓN 21 ARTÍCULO 1 69 ARTÍCULO 2 75 MANUSCRITO 3 83 MANUSCRITO 4 103 MANUSCRITO 5 123 CONCLUSIONES 145
INTRODUCCIÓN
INTRODUCCIÓN 21 1. El sector caprino 1.1. El caprino a nivel mundial 1.1.1.Generalidades Lacabrafuedelosprimerosanimalesdomesticadosporelhombre,haceunos10500años, contribuyendoaldesarrollodelaagriculturaduranteelperiodoneolítico(Fernándezycol.,2006). Desde entonces entró a formar parte de la alimentación del ser humano, proporcionándole leche ycarne,ademásdepiel,peloyestiércol(VigneyHelmer,2006).Laimportantecontribucióndela ganadería caprina al sostenimiento alimentario de la humanidad ha hecho que en la actualidad se encuentre en regiones geográficas que difieren notablemente en clima, topografía y fertilidad, debido asugranrusticidadyadaptabilidad(Devendra,1987). Las cabras pueden adaptarse a una amplia gama de sistemas de intensificación que van de un extremo al otro: por un lado, las razas lecheras mejoradas explotadas en condiciones intensivas en las zonas templadas de Europa o América del Norte, en ciertas zonas favorables de clima tropical húmedo,oensuperficiesirrigadasdeclimatropicalsecoy,porotrolado,laspoblacioneslocalesque se mantienen en regiones muy áridas en las que los demás rumiantes difícilmente pueden resistir, talescomolaszonasdesérticasdeÁfricaodelMedioOriente(BoyazogluyMorand-Fehr,1987). 1.1.2.Poblacióncaprinayproducciónlechera La población caprina a nivel mundial ha incrementado su censo de forma importante durante losúltimos40años,muchomásqueloscensosdebovinoyovino(Tabla1),locualsugiereelcreciente interésporpartedelapoblaciónenlosproductoslácteosderivadosdelacabra(Dubeuf,2005). Tabla 1. Población mundial de bovino, ovino y caprino en los últimos 40 años (millones de cabezas). (FAOSTAT, 2011). Año Bovino Ovino Caprino 2010 1427,5 1078,3 909,8 2000 1313,2 1059,7 751,4 1990 1298,4 1207,9 591,1 1980 1217,0 1098,7 464,3 1970 1081,6 1063,3 377,7
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 22 Sinembargo,ladistribucióndelcaprinoesbastantedesigualanivelmundial.SegúnlaOrganizacióndelasNacionesUnidasparalaAlimentaciónylaAgricultura(FAO),enelaño2011Asia concentrabael61,6%delcensototal,mientrasqueÁfricacontabaconel31,6%.Encontraste,Europa yAméricasólotienenel1,9%y4,3%,respectivamente.Así,paísescomoChina,India,Pakistán,Bangladesh,yNigeria(Figura1)estánalacabezaencuantoapoblacióndecabras,representandoun valioso sustento para numerosas familias de escasos recursos. Figura1.Principalespaísesenpoblacióncaprinaenelaño2011.(FAOSTAT,2011). DeacuerdoconlaFAO,laproduccióndelechedecabraenelmundoduranteelaño2011fue deaproximadamente15millonesdetoneladas,loquerepresentóel2,2%deltotaldelalecheproducidaanivelmundial.Europa,consóloel5%deltotaldelganadocaprinolechero,produjocasiel20% del volumen de leche total de esta especie. Cabe señalar, que en algunos países de África y Asia, las estadísticas no registran el verdadero valor de la producción, debido a la dificultad para hacer los censos, por la dispersión de los rebaños, y porque prácticamente toda la leche se destina al consumo de la unidad familiar. 1.1.3.Biodiversidadcaprina Entrelos900millonesdecabrasanivelmundial,untotalde570razashansidodefinidas.Los paísesenvíasdedesarrolloconcentranel60%deltotaldelasrazas(Galal,2005).EnEuropaseencuentran los genotipos con mayor producción lechera como la Saanen, Alpina, Nubia o Toggenburg (Figura2).Sinembargoestecontinenteposeelamenordiversidadgenética,debidoalosprocesosde mejora productiva, en los que han desaparecido las razas menos competitivas.
INTRODUCCIÓN 23 Figura2.Principalesrazascaprinaslecheras.A:Saanen;B:Alpina;C:Nubia;D:Toggenburg.(BreedStandards, www.dairygoatjournal.com). 1.2. El caprino en España 1.2.1.Generalidades Durante muchos años, la cabra en España ha jugado un destacado papel en el abastecimiento de leche para el consumo de la población. La leche obtenida era destinada al consumo familiar, mayoritariamentedeformadirecta,aunqueunafracciónvariablesegúncasos,eratransformadaenqueso, elaboradoenlapropiaexplotaciónpormétodosartesanales(Esteban-Muñoz,2008).Laganadería caprina ha estado ligada tradicionalmente a zonas rurales poco productivas desde el punto de vista agrícola, dado que las cabras tienen una gran capacidad para el aprovechamiento de los pastos de escasa calidad. Esta característica ha hecho que el ganado caprino jugase un papel importante en el mantenimientodezonasmarginalesydelapoblaciónasociadaaellas.Aúnhoyendía,enEspaña,el 86%delapoblacióncaprinaseencuentraenlasllamadasáreasmenosfavorecidas(Rancourtycol., 2006),aunquelossistemasdeexplotaciónhancambiadosustancialmente. 1.2.2.Poblacióncaprinayproducciónlechera EnEspaña,segúnlaFAO,lapoblacióndecaprinosdeaptitudlecheraseestimóalrededorde los1,2millonesdecabezasenelaño2011.Laevolucióndelcensocaprinoenlosúltimos20años(Figura3)hasufridooscilacionessignificativas,comoconsecuencia,entreotrosaspectos,delavariabilidadenlospreciosdelaleche.Sinembargo,laproducciónlecherasobrepasólas540000toneladas enel2011,conunincrementoanualmediodel4%durantelasúltimasdosdécadas,principalmente debido a la mejora genética y alimenticia, lo cual ha permitido optimizar el rendimiento lechero.
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 24 Figura3.EvolucióndelganadocaprinolecheroyproduccióndelechedecabraenEspañaenlosúltimos20años. (FAOSTAT,2011). Ladistribucióndelcaprinoenlageografíaespañolaesmuyirregular(Figura4).EnCanariasy enelsurdelaPenínsulaIbéricaseconcentraalrededordel80%delcensodecabras.Lalargatradición de los cabreros de dichas áreas geográficas y la presencia de razas caprinas de alta producción de leche, además de la situación agroclimática, han favorecido el desarrollo del caprino en estas regiones(Esteban-Muñoz,2008). Figura4.Distribucióndelganadocaprinoporcomunidadesautónomasen2011.(MAGRAMA,2011). Introducción Página9 Figura 3. Evolución del ganado caprino lechero y producción de leche de cabra en España en los últimos 20 años. (FAOSTAT, 2011). La distribución del caprino en la geografía española es muy irregular (Figura 4). En Canarias y en el sur de la Península Ibérica se concentra alrededor del 80% del censo de cabras. La larga tradición de los cabreros de dichas áreas geográficas y la presencia de razas caprinas de alta producción de leche, además de la situación agroclimática, han favorecido el desarrollo del caprino en estas regiones (Esteban-Muñoz, 2008). Figura 4. Distribución del ganado caprino por comunidades autónomas en 2011. (MAGRAMA, 2011). 200 400 600 800 1000 400 800 1200 1600 2000 1991 1995 1999 2003 2007 2011 Milesdetoneladasdeleche Milesdecabezasdeganado Año Ganadocaprinolechero Producciónlechera Introducción Página9 Figura 3. Evolución del ganado caprino lechero y producción de leche de cabra en España en los últimos 20 años. (FAOSTAT, 2011). La distribución del caprino en la geografía española es muy irregular (Figura 4). En Canarias y en el sur de la Península Ibérica se concentra alrededor del 80% del censo de cabras. La larga tradición de los cabreros de dichas áreas geográficas y la presencia de razas caprinas de alta producción de leche, además de la situación agroclimática, han favorecido el desarrollo del caprino en estas regiones (Esteban-Muñoz, 2008). Figura 4. Distribución del ganado caprino por comunidades autónomas en 2011. (MAGRAMA, 2011). 200 400 600 800 1000 400 800 1200 1600 2000 1991 1995 1999 2003 2007 2011 Milesdetoneladasdeleche Milesdecabezasdeganado Año Ganadocaprinolechero Producciónlechera
INTRODUCCIÓN 31 Elprototiporacialrespondealassiguientescaracterísticas(Figura11):Cabezadetamaño grande, con perfil fronto-nasal recto o subconvexo, con orejas grandes e inclinadas hacia abajo. Los cuernos pueden ser tipo prisca o de tipo aegagrus, en arco hacia atrás. La línea dorso-lumbar es recta. El pelo se presenta generalmente uniforme, corto y raso, y capa policromada. Ubre de color negro o pizarra, tipo globosa o abolsada, de amplia inserción, con pezones bien diferenciados y, a veces de implantaciónlateral(Esteban-Muñoz,2008). Figura11.CabraMajorera.(FEAGAS). LaproducciónmediadelascabrasderazaMajoreraesde551,3kgdelecheen210díasde lactación.Porotraparte,unelevadoporcentajedecabrasmantienenduranteeseperiodounaproducciónmediasuperiora2kgdelechepordía.Conunacomposiciónmediadelalechede:Grasa= 3,94%;Proteína=3,90%;Lactosa=4,55%;ExtractoSeco=13,19%(Fresno,1993). Hay que tener en cuenta que una buena parte de la leche de estas cabras es destinada a la elaboración de queso artesanal o industrial, el cual se consume después de unos días de oreo, o bien se deja madurar largo tiempo, en ambiente templado y seco. El queso que se va a conservar más tiempo puede untarse con aceite, pimentón y/o gofio, lo que le confiere características peculiares. Su masa al corte aparece compacta, de textura cremosa y sabor acídulo y algo picante. Es de color blanco,tomandounligerotonomarfileñoenquesoscurados(FresnoyÁlvarez,2007).
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 32 ∑ Raza Palmera. TienesuorigenenlapoblacióncaprinaprehispánicaenlaisladeLaPalma.Alserestaislaun lugardepasoenlasrutasvelerascondestinoaAmérica,larazaPalmerasevioinfluenciadaporlas razasdelsuroestedelaPenínsulaIbérica.Sinembargo,estegenotipotuvounmayoraislamientoque las otras razas canarias, lo que la aproxima más a la cabra prehispánica, y sustenta su diferenciación genética, que permite una extraordinaria rusticidad y capacidad de adaptación a zonas abruptas de montaña(Martínezycol.,2006). En la década de los setenta la raza experimentó cruces con animales pertenecientes a la poblaciónMajoreraconobjetodeaumentarlaproduccióndeleche,debidoalaerróneapolíticaenese momento de considerar a las tres razas canarias como una sola. Aquellos cruzamientos implicaron un trabajo posterior enorme y complicado, aunque afortunadamente con resultados satisfactorios, para eliminar los genes foráneos ya que los híbridos no se adaptaban a las condiciones de explotación de laIsladeLaPalma(Capoteycol.,1993). Elprototiporacialrespondealassiguientescaracterísticas(Figura12):Cabezadetamaño pequeño, corta y ancha, con perfil fronto-nasal recto o subcóncavo, orejas más bien cortas y una cornamenta destacada, con predominancia del tipo heteronima. Tronco largo, con línea dorso-lumbar recta. En sus capas predomina el color rojizo y el pelo es de longitud media. Ubre más recogida que en las otras razas canarias, de tipo globosa, color negro o pardo, y con pezones más bien pequeños (Esteban-Muñoz,2008). Figura12.CabraPalmera.(CRDOPQuesoPalmero).
INTRODUCCIÓN 33 Laproducciónmediatipificadaa210díasdelactación,esde362,6kgdeleche,conunaproduccióndegranpersistencia,loquepermiteampliarelperiododelactacióna240-270días.Lacalidad mediadelalecheesde:Grasa=4,06%;Proteína=4,21%;Lactosa=4,66%;ExtractoSeco=13,75% (Fresno,1993). LaproduccióndelechedelacabraPalmeravadestinadaalafabricacióndequesodetipo artesanal. Se trata de un queso graso o extragraso, elaborado con leche cruda y entera, y se comercializatantotierno(de8a20días),comosemicurado(21a60días)ycurado(apartirde60días). El sabor es franco y láctico, muy mantecoso y con un ligero y agradable aroma ahumado (Fresno y Álvarez,2007). ∑ Raza Tinerfeña. SibienenelCatálogoOficialesconsideradacomounaúnicapoblación,estudiosmorfológicos y genéticos señalan suficientes evidencias para considerar dos grupos independientes en el norteysurdelaisladeTenerife(Capoteycol.,1998;Martínezycol.,2006).Así,existiríaelecotipo Norte, con gran influencia del tronco pirenaico, y el ecotipo Sur, reducido en pureza por sus cruces concabraMajorera.Aligualquelasotrasdosrazas,lacabraTinerfeñapresentaunagranrusticidad y elevada aptitud para la producción de leche. Elprototiporacialtienelassiguientescaracterísticas(Figura13):Cabezadetamañoproporcionado con el cuerpo, el ecotipo Norte dispone de un perfil fronto-nasal recto o subconvexo, mientrasqueenelSurcasisiempreesrecto.Ambastienencornamentatipoprisca.Orejasdegrantamaño, inclinadas hacia abajo en las cabras del Norte, y de menor tamaño en cabras de la zona Sur. Los caprinos del Norte se caracterizan por presentar pelo largo y colores oscuros, principalmente negro y con alguna frecuencia castaño. Los caprinos del Sur tienen el pelo corto y disponen de una capa multicolor.Laubredeestascabras,engeneralpresentanuntiposimilaraldelacabraMajorera,con pezones pequeños y situados con alguna frecuencia en posición lateral. En la cabra Tinerfeña Norte, la forma de la ubre, frecuentemente globosa, es más adecuada para el ordeño mecánico en lo referentealtamañoyposicióndelospezones,quesuhomólogadelSur(Esteban-Muñoz,2008). LosvaloresasignadosalaproduccióndelechedecabraTinerfeñaen210díasdelactación, esde421,0kgdeleche,conunacomposiciónde:Grasa=3,91%;Proteína=3,79%;Lactosa=4,46%; ExtractoSeco=13,13%(Fresno,1993).EnlaisladeTenerife,seelaboraelQuesodeTenerife,obtenido
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 34 con leche cruda de cabra. Se trata de un queso de graso a extragraso y que se consume preferentemente fresco o ligeramente curado, de color blanco intenso y brillante, y sabor muy fresco y acidulado,ligeramentesaladoygrasolechosoalpaladar(FresnoyÁlvarez,2007). Figura13.Cabra Tinerfeña Norte. (ACRICATI). 2. La leche de cabra En términos generales, la leche de cabra es un líquido blanco opaco, de un sabor ligeramente azucarado, cuyo olor es poco marcado cuando es recogida con limpieza de animales que tengan un buen estado de salud. La consistencia es uniforme sin grumos ni copos. De la calidad de la leche empleada en queserías va a depender gran parte el éxito de las transformaciones y la calidad del producto final. Nutricionalmente, la leche de cabra es una fuente de proteínas de alto valor biológico y ácidos grasos esenciales, además de minerales y vitamina A. Es de gran importancia para los infantes por su alto valor nutricional, hipoalergenicidad, así como por su alta digestibilidad debido al pequeño tamaño de los glóbulos de grasa. Algunos autores han resaltado las propiedades saludables delalechedecabra(Silanikoveycol.,2010)ysusproductosderivados(RibeiroyRibeiro,2010),justificando su alta calidad y los beneficios de su consumo. Además, la población del mundo desarrollado no se preocupa especialmente sobre el costo de los productos en el mercado si al consumir deriva-
INTRODUCCIÓN 35 doslácteosdecabraspuedeobtenerbeneficiosparalasalud(Mowlen,2005).Actualmenteexisten revisionesquehanprofundizadoenlascaracterísticasfísico-químicas(Parkycol.,2007),reológicas (Park,2007)ehigiénico-sanitarias(Raynal-Ljutovacycol.,2007)delalechedecabra. 2.1. Composición química La leche está compuesta principalmente, además del agua, por materia grasa, proteínas, lactosa, sales minerales, vitaminas, y enzimas. La composición varía apreciablemente de acuerdo a algunos factores como la raza, la alimentación, el período de lactación, la frecuencia de ordeño, el estado sanitario de la cabra, entre otros. 2.1.1.Grasa El contenido de grasa es el componente más variable cuantitativa y cualitativamente en la leche. Los glóbulos de grasa de la leche de cabra son en general más pequeños y más finos que en lalechedevaca(3,5vs.4,6µm,respectivamente)(Park,2006).Acausadesureducidotamañoyla uniformidad de su distribución, los glóbulos de la leche de cabra ingerida quedan más dispersos y, como resultado, las enzimas digestivas humanas, al actuar sobre ellos, los desintegran de forma más rápida y completa. No se han encontrado diferencias apreciables en el mecanismo de secreción de los glóbulos de grasa en cabra, oveja y vaca, teniendo estos glóbulos una estructura y composición similar entre lastresespecies(Scolozziycol.,2003).Respectoalosácidosgrasosqueformanpartedelaleche decabra,cincodeellosrepresentanmásdel75%:cáprico(C10:0),mirístico(C14:0),palmítico(C16:0), esteárico(C18:0)yoleico(C18:1)(Chilliardycol.,2006). 2.1.2.Proteína En cuanto a las proteínas de la leche, éstas se dividen habitualmente como caseínas y proteínas séricas, aunque se pueden encontrar otras proteínas minoritarias, como inmunoglobulinas, lactoferrina, transferrina, ferritina, peptona proteasa, prolactina, etc. El contenido total de proteínas es uno de los principales criterios de calidad usados como sistema de pago de la leche de cabra en muchospaíses(Pirisiycol.,2007).
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 36 Engeneral,laß-caseínaeslaprincipalcaseínaenlalechedecabra(Tziboula-Clarke,2003). Laproporcióndelas4caseínasmayoritariasenlalechedecabraestádeterminadaporpolimorfismos genéticos, pero en general el orden es ß-caseína > αS2-caseína > αS1-caseína>k-caseína.De media, la αS1-caseínarepresentael10%deltotaldelascaseínas,variandode0a25%(Boulangery col.,1984),dependiendodelgenotipodelanimal.Lasrazascaprinascanarias(Majorera,Tinerfeñay, especialmente,Palmera)representanuncasoparticulardondeel60%delosalelosdelaαS1-caseína caprinasondeltipoAyB(Jordanaycol.,1996),porloqueestacaseínaesrelativamenteabundante en la leche y quesos elaborados a partir de estos animales. 2.1.3.Lactosa La lactosa es el carbohidrato por excelencia en la leche, el cual está formado por una molécula de glucosa y otra de galactosa, que también pueden estar presentes de forma individual en pequeñascantidadeslibres(Park,2006).Lalactosaesdegranimportanciaparamantenerelequilibrio osmótico entre la corriente sanguínea y las células alveolares de la glándula mamaria durante la síntesisdelaleche,ysusecreciónenellumenalveolaryelsistemadeconductosdelaubre(Parky col.,2007).Encabrasesueleencontrarsobre0,2-0,5%menosqueenlalechedevacayoveja.Otros carbohidratos presentes en la leche de cabra son los oligosacáridos, glicopéptidos, glicoproteínas y nucleótidos(Parkycol.,2007),perosusfuncioneshansidomuypocoestudiadas. 2.1.4.Vitaminasyminerales El contenido de macrominerales en la leche de cabra es mucho mayor que el de la leche humana, con cuatro y seis veces más calcio y fósforo, respectivamente. Comparativamente, la leche de cabra contiene más calcio, fósforo, potasio, magnesio y cloro, y menos sodio y azufre que la leche de vaca(Parkycol.,2007).Debidoaquelascabrasconviertentodoelβ-carotenoenvitaminaA,laleche de cabra presenta mayor cantidad de este compuesto y es mucho más blanca que la leche de vaca. Tambiéncontienemástiamina,riboflavina,niacina,vitaminaCyvitaminaDquelalechedevaca(Park ycol.,2007).
INTRODUCCIÓN 37 2.2. Células somáticas Las células somáticas están presentes en la leche de todos los mamíferos, no tienen capacidadparamultiplicarseyprovienendelpropioanimal.Segúnsuorigen,seclasificanendosgrandes grupos: células de origen sanguíneo y células epiteliales. Normalmente estas células se encuentran en la glándula mamaria sana, aunque puede considerarse un indicador de inflamación y/o infección debido a que en estas situaciones se produce un incremento en el trasvase de leucocitos a la leche (DasySingh,2000). En muchos países se han establecido unos criterios de calidad para la leche de acuerdo a los requerimientos higiénicos, tecnológicos y sensoriales. Estos criterios forman parte de un sistema de pago que asegura la calidad de los productos finales. En los Estados Unidos, el límite legal en el recuento de células somáticas (RCS) establecido en leche de cabra por la FDA (Food and Drug Administration)esde1millóndecélulas/ml.SinembargoenlaUniónEuropeanohaylímiteparalaleche de cabras y ovejas, como está dispuesto en los diferentes reglamentos, que establecen los criterios generalesyespecíficosdehigienequedebencumplirlosproductosalimenticios(Paapeycol.,2007). Algunosautores(Paapeycol.,2007;Raynal-Ljutovacycol.,2007)haninformadoqueloscabreros de Estados Unidos tienen dificultades para mantener el RCS en la leche de tanque por debajo del límite establecido. Como consecuencia, muchas granjas eliminan la leche que excede el límite, lo cual provoca importantes pérdidas económicas para el sector. El alto RCS puede ser causado por infección pero también por razones fisiológicas. En las ubressanasdecabras,elRCSseincrementaprogresivamenteconlaedad(Salamaycol.,2003),durantelalactación(Gomesycol.,2006),ademásdefluctuacionesdeundíaparaotro(Zengycol.,1997), enlaqueintervienenfactorescomoelcelo(Mehdidycol.,2013)yelestrés(McDougallycol.,2002). Portanto,laaplicacióndeuncriterioparalaevaluacióndelacalidaddelalecheyparaladetección de mastitis está sin resolver. En España ya hay algunas industrias queseras que están pagando la leche de cabra a los ganaderossegúnsucomposiciónquímicabásica(grasayproteína)asícomoenfuncióndelacalidad higiénico-sanitaria (microbiología, RCS), pudiendo aplicarse primas o penalizaciones, tal como se recoge en la homologación de contrato-tipo de suministro de leche de cabra con destino a su transformaciónenproductoslácteos(OrdenARM/2387/2010,de1deSeptiembre).
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 38 3. Factores que afectan al rendimiento y composición de la leche La cantidad de leche producida por una cabra y su composición tienen variaciones como consecuenciadeungrannúmerodefactores.Estospuedenactuaraisladamenteoencombinación. Clásicamente, los mencionados factores se han dividido en dos grupos, uno de carácter intrínseco, atribuido al animal, y otro de carácter extrínseco, debido a las condiciones y circunstancias externas queactúansobreél. 3.1. Factores intrínsecos 3.1.1.Razaeindividuo La producción lechera caprina está condicionada por factores genéticos que influyen tanto sobrelacantidad(Figura14)comoenlacalidaddelalecheproducida.Sinembargo,lasdiferentes condiciones de cría, alimentación, factores geográficos y climáticos a las que están expuestas las diferentes razas, hacen difícil evaluar la importancia de este factor, de tal manera que la mayoría de diferencias dentro de cabras de la misma raza pueden ser explicadas por el efecto rebaño (Capote y col.,2000). Figura14.Curvasdelactacióndealgunasrazasdealtaproducción.(AnimalImprovementProgramsLaboratory,2004). Introducción Página27 3.1. Factores intrínsecos 3.1.1. Raza e individuo La producción lechera caprina está condicionada por factores genéticos que influyen tanto sobre la cantidad (Figura 14) como en la calidad de la leche producida. Sin embargo, las diferentes condiciones de cría, alimentación, factores geográficos y climáticos a las que están expuestas las diferentes razas, hacen difícil evaluar la importancia de este factor, de tal manera que la mayoría de diferencias dentro de cabras de la misma raza pueden ser explicadas por el efecto rebaño (Capote y col., 2000). Figura 14. Curvas de lactación de algunas razas de alta producción. (Animal Improvement Programs Laboratory, 2004). Las cabras de alta producción lechera más difundidas en el mundo tienen su origen o se han seleccionado esencialmente en tres países: Suiza (Saanen y Toggenburg), Francia (Alpina) e Inglaterra (Anglonubia). Sobre estos animales se han realizado una gran cantidad de estudios que abarcan la mayoría de los aspectos relacionados con los individuos y su explotación, destacando aquellos dedicados a la 0,0 1,0 2,0 3,0 4,0 0 50 100 150 200 250 300 350 Produccióndeleche(Kg) Díasdelactación Alpina Nubia Saanen Toggenburg
INTRODUCCIÓN 39 Las cabras de alta producción lechera más difundidas en el mundo tienen su origen o se han seleccionado esencialmente en tres países: Suiza (Saanen y Toggenburg), Francia (Alpina) e Inglaterra (Anglonubia). Sobre estos animales se han realizado una gran cantidad de estudios que abarcan la mayoría de los aspectos relacionados con los individuos y su explotación, destacando aquellosdedicadosalaproducciónlechera(Britoycol.,2011;Garcia-Penicheycol.,2012).Enlos países, cuyas razas nativas son muy poco productivas, suele ser frecuente el cruzamiento con razas mejoradas(Kumeycol.,2012;Sanogoycol.,2012).Ladiscutiblefinalidaddeestoscruzamientosesla de conservar las cualidades de rusticidad y adaptación al medio de las razas nativas pero mejorando la producción lechera y alargando el tiempo de lactación. Lacomposiciónquímicadelalechetambiénpresentagrandesvariacionessegúnlaraza, ligadasalniveldeproduccióndeleche.Enestesentido,Garcia-Penicheycol.(2012)examinaronla composicióndelalecheenvariasrazasdealtaproduccióndurante3periodos(de1976a1984,de 1985a1994,yde1995a2005),yobservaronincrementosenelporcentajedeproteína,elcualfuevariablesegúnlasrazas(7,4%enToggenburg;7,1%enAlpina;6,5%enLaMancha;5,6%enAnglonubia; 3,4%enSaanen).Sinembargo,sóloencontraronincrementosenelporcentajedegrasaenunaraza (2,1%enAnglonubia). El estudio detallado de las variantes genéticas de la caseína as1(Ambrosoliycol.,1988;Jordanaycol.,1996)permitiórealizarunanuevaclasificacióndelasrazascaprinasenfuncióndesus frecuencias alélicas. Cabe destacar que la concentración de as1secorrelacionapositivamentecon las propiedades de coagulación de la leche, y que nuevos trabajos genéticos están enfocados en la mejoradeestavariable(Magaycol.,2009). Así como existe variabilidad entre razas en cuanto a producción y calidad de la leche, también existen variaciones entre animales de la misma raza, pudiendo incluso superar estas variaciones a las interraciales. 3.1.2.Estadoyduracióndelalactación La producción de leche no es constante a lo largo de toda la lactación. De manera general la producción aumenta hasta alcanzar el máximo pico de producción, luego desciende a medida que avanza la lactación. El aumento de la producción de leche hasta el pico de lactación parece ser debido a una mayor capacidad de síntesis de las células epiteliales mamarias, en lugar de un incremento
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 40 enelnúmerodecélulassecretoras(Capucoycol.,2001;Salama,2005).Posteriormente,eldescenso progresivo de la producción de leche, tras alcanzar el máximo, es asociado con una reducción en el contenidodeADNtotaldelparénquimamamario,implicandounadisminuciónenelnúmerodecélulassecretoras(KnightyPeaker,1984;Capucoycol.,2001). Lamayoríadelascabrassitúansumáximaproducciónentrela3ªy8ªsemanadelactación (Salama,2005).Así,sehanobtenidovaloresdepicodelactaciónde2,42kgalos45días(Leónycol., 2012)encabrasMurciano-Granadina,de2,48kgalos45díasencabrasTinerfeñas(Capoteycol., 2000),ode2,54kgalos54díasencrucedeToggenburgconrazaslocalesdeMéxico(Montaldoycol., 1997).DeacuerdoalDepartamentodeAgriculturadeEstadosUnidos,losmáximosvaloresdeproducciónalcanzadosparacabrasmultíparassonde4,63kgalos50díasenSaanen,4,49kgalos40días enAlpina,yde3,67kgalos45díasenOberhasli(AnimalImprovementProgramsLaboratory,2004). En lo que respecta a la composición, el contenido de grasa sigue una evolución opuesta a la evolución de la producción de leche, es decir, una rápida disminución en el transcurso de las primeras semanas de lactación, a la que sigue un mínimo que se alcanza aproximadamente entre el finaldel2ºyel6ºmesdelactación,yposteriormente,unaumentolentoyprogresivo(Peris,1994).Sin embargo, algunos autores no consiguieron observar diferencias de este componente entre las fases delactacióntemprana,mediaotardía(Capoteycol.,2008).Encuantoalaproteína,lamayoríadelos autores encontraron que permanece casi constante con pequeñas fluctuaciones alrededor de un valormedio(Peris,1994;Hejtmankovaycol.,2012).Finalmente,laevolucióndelalactosapresenta un comportamiento inverso al de la grasa, es decir aumentando en la primera parte de la lactación y disminuyendoenlaúltima(Parkycol.,2007). 3.1.3.Edadynúmerodelactación Parececlaroquelaproduccióndelecheesmenorencabrasprimíparasqueencabrasmultíparas(Goetschycol.,2011).Dehecho,lasúnicasdiferenciassignificativassehanobservadoentrela primerayelrestodelaslactaciones(ZengyEscobar,1995).Ellopuededeberseaqueentrelaprimera y segunda lactación los animales manifiestan una importante diferencia en el desarrollo corporal, más acentuada en cabras que se cubren precozmente de forma sistemática, como ocurre en las Islas Canarias(Capoteycol.,2000),Portanto,lascabrasenprimeralactacióntienenmenorvolumende ubre(Salamaycol.,2004)yportantounamenorcantidaddelechesecretadaporunidaddevolumen
INTRODUCCIÓN 47 enlabúsquedadezonasdepastoreo.Sinembargo,lasmejorastecnológicasproducidasenelsector caprinoenlosúltimosañosconlaproliferacióndemaquinariadeordeño,tanquesderefrigeracióne industrias con circuito de recogida de la leche, suponía que la variación en la frecuencia de ordeño permitiría aumentar los rendimientos de los rebaños, pero los primeros estudios realizados en cabras Tinerfeñasconsiguieronincrementosentresóloel6y8%(Capoteycol.,2000). 4. Estructura anatómica y conformación de la glándula mamaria 4.1. Anatomía de la glándula mamaria caprina La ubre caprina, conformada por dos glándulas independientes, está situada en la región inguinal cubriendo la cara interna de los muslos y con una proyección desde atrás hacia adelante. Cada glándula mamaria está compuesta por una cisterna y una papila o pezón, y se separa de la otra por un surco intermamario. En las cabras, al igual que en el resto de las hembras con aptitud lechera, el desarrollo mamario constituye la base donde podrá proliferar el tejido secretor (Knight yPeaker,1982). Cada complejo mamario se compone de diversos elementos funcionales responsables del procesobiosintético,almacenamientoytransportedelaleche(Figura19): Figura19.Vistalateralglándulamamariacaprina.A:parénquimamamario;b:porcióncisternaldelsenolactífero;c:porciónpapilardelsenolactífero;d:papilamamaria;e:nóduloslinfáticosmamarios;f:conductoyorificiopapilar;g:conductoslactíferoscolectores.(Sandoval,2003).
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 48 4.1.1.Parénquimaglandular En el parénquima glandular o tejido noble se encuentran las unidades secretoras, o alvéolos, que presentan como característica primordial la presencia de un epitelio secretor que delimita internamente el lumen donde se deposita la leche secretada por la células. Exteriormente cada alvéolo presenta una compleja red de capilares arteriales y venosos que están en íntimo y estrecho contacto conelepiteliobasal(ConstantinescuyConstantinescu,2010).Losalvéolosagrupadosenracimos, lobulillos y lóbulos, son vaciados por pequeños canalículos que confluyen para formar conductos de mayor tamaño, llamados canales galactóforos, los que a su vez convergen en estructuras de mayor diámetrointerno,conlímitesmásdifusosdenominadoscisternasdelamama(FerrandoyBoza,1990). Finalmente este sistema de conducción se comunica con una cisterna del pezón, ubicada en esteúltimoycuyovolumenvaríasegúneltamañodelpezón.Elinteriordelapapilamamariapresenta una mucosa muy plegada para evitar el flujo espontáneo de leche al exterior así como la penetración de agentes patógenos, y una concentración de fibras musculares que contienen numerosas terminacionesnerviosasyvasossanguíneos(Suárez-Trujilloycol.,2013). Otroelementoanatómicofuncionaldeimportancialoconstituyenlascélulasmioepiteliales que envuelven externamente a los alveolos y que por ser fibras musculares lisas responden activamente a las descargas de oxitocina, permitiendo un correcto vaciamiento de la leche acumulada en lasestructurasnocisternales(BruckmaieryBlum,1998). 4.1.2.Sistemasuspensorio El aparato suspensorio de la ubre lo conforma una red de fibras de naturaleza elástica y fibrosa, procedentes de la pared ventral del abdomen, que penetran en el parénquima mamario a diferentes niveles, evitando que los cuerpos glandulares graviten directamente sobre la piel que los envuelve(Suárez-Trujilloycol.,2013).Laproporcióndetejidoglandularydetejidodesosténpresenta una buena caracterización de una glándula mamaria en cuanto a su mayor o menor capacidad productiva. Así una glándula con una gran cantidad de tejido de sostén presentará un aspecto exterior con escasa variación antes o después del ordeño, mientras que una glándula rica en tejido noble presentaráunaspectomuyretraídodespuésdelordeño(FerrandoyBoza,1990).
INTRODUCCIÓN 49 4.1.3.Sistemacirculatorioylinfático Parapodersintetizarlaleche,debecircularporlaubreunaenormecantidaddesangre,ya que se requiere una elevada proporción de nutrientes para que las células secretoras la produzcan. Así mismo, las células alveolares requieren tiempo para la captura de estos nutrientes, por lo que un pasodesangreaaltavelocidadnoresolveríaelproblema.Paraquelasecreciónlácteasellevea cabo eficientemente, el aporte sanguíneo se ralentiza a nivel alveolar como consecuencia del enorme desarrollo del sistema venoso de la ubre, encontrándose alrededor de las mamas, ricas redes capilares conectadas con amplios plexos venosos por los que la sangre circula muy lentamente (FerrandoyBoza,1990). También cabe destacar la existencia de una gran representación linfática, destacando los ganglioslinfáticosmamariosqueactúancomolinfocentros,yquedesempeñanunimportantepapel como barrera defensiva frente a las infecciones que puedan afectar a la ubre (Constantinescu y Constantinescu,2010). 4.2. Morfología de la ubre de las razas canarias La morfología de la ubre es un importante parámetro en la ganadería caprina por su contribución en la producción de leche y la aptitud de ésta para el ordeño mecanizado. Los parámetros más utilizados en la definición de la morfología de la ubre son: profundidad y volumen de la ubre, morfología del pezón (longitud, anchura, ángulo de implantación y situación antero-posterior), y altura de las cisternasmamarias(Figura20). Una morfología de ubre adecuada es muy importante para una buena adaptación del animal a la máquina de ordeño, ya que puede evitar algunos efectos indeseables, como por ejemplo la inhibición del reflejo de eyección láctea, o la caída de pezoneras que conllevaría un mayor tiempo de ordeño(Barillet,2007).Peris(1994)alestudiarlaaptitudalordeñomecánicodecabrasMurcianoGranadina,describióqueexisteunagranheterogeneidadenloscriteriosmetodológicosylasmedidas morfológicas evaluadas, así como en el estado de lactación utilizado por cada autor para evaluar la aptitud al ordeño.
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 50 Figura20.Medidasmorfológicadelaubre.DEP:distanciaentrepezones;ACS:alturacisterna-suelo;APS:alturapezónsuelo;AIUS:alturainserción-suelo;PU:profundidadubre.(U.D.ProducciónAnimalULPGC). La morfología de la ubre ha sido descrita en las principales razas lecheras: Saanen y Alpina (Manfrediycol.,2001),Toggenburg(Wang,1989),Murciano-Granadina(Perisycol.,1999).Enlostrabajos se describen distintas formas de ubres: redondeadas o globosas, ovales, piriformes, pendulares o planas. También diferentes tipos de pezón: cónicos, cilíndricos, en forma de botella o bulbosos, pequeños, o voluminosos. En el caso de la razas canarias, la ubre se caracteriza porque la altura del pezónesmayorquelaalturadelfondodecisternaenungrannúmerodeanimales(Figura21),una circunstancia negativa en el momento del ordeño, ya que es necesaria la intervención manual para levantar la ubre y extraer la porción de leche que hay debajo del pezón, lo cual incrementa el tiempo deordeño(Capoteycol.,2008).
INTRODUCCIÓN 51 Figura21.Típicaubredelascabrascanarias.(U.D.ProducciónAnimalULPGC). Algunos autores han señalado que la selección genética para mejorar la producción lechera llevadaacaboenlasúltimasdécadas,haproducidoefectosindeseablesenlamorfologíamamaria, como la tendencia de que las ubres tengan ubicados los pezones más horizontalmente para incrementar la capacidad cisternal pero que trae como consecuencia una menor ordeñabilidad de los animales(MarnetyMcKusick,2001;Barillet,2007). 5. Fisiología de ordeño El inicio masivo de la secreción láctea corresponde al momento del parto en que se produce un cambio hormonal importante, con el descenso en el nivel de la progesterona y un incremento de estrógenos,prolactina,yglucocorticoides(Davisycol.,1979).Lalactogénesiscomprendelasíntesis intracelular de la leche y su posterior transferencia desde el citoplasma hacia el lumen alveolar. El componente de base del tejido secretor es el alvéolo, envuelto por una capa de células mioepiteliales que ayudan en la contracción de los alvéolos por efecto de la oxitocina, produciendo la expulsión de la leche hacia los conductos galactóforos. Este proceso neurohormonal es provocado por estímulos comoelamamantamientodelacríaoelprocesodeordeño(ParkyHaenlein,2010). Las terminaciones nerviosas del pezón están conectadas con el sistema nervioso central y el hipotálamo a través de las raíces dorsales de los nervios lumbares de la médula espinal. Cuando un estímulo alcanza el sistema nervioso central provoca que el lóbulo posterior de la hipófisis libere
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 52 oxitocina. La oxitocina viaja a través del flujo de sangre hasta la glándula mamaria, donde causa la contraccióndelascélulasmioepiteliales(Figura22)(BruckmaieryBlum,1998). Figura22.Esquemadeeyeccióndelecheencabras.(Caja,2003). 5.1. Efectos de la oxitocina sobre la eyección de leche La oxitocina es un neuropéptido responsable de la eyección de la leche, con el consecuente vaciado de la ubre. Dependiendo del grado de estimulación de la glándula mamaria, se producen diferentes respuestas en la liberación de oxitocina. De esta forma, el amamantamiento de la cría es un estímulo más potente que el ordeño, mientras que el ordeño manual induce una liberación más pronunciadadeoxitocinaqueelordeñoamáquina(BruckmaieryBlum,1998).Además,laestimulación previa al ordeño es importante en algunas especies como el ganado bovino porque aumenta los niveles de oxitocina y promueve la inducción temprana de eyección de la leche para evitar una interrupción del flujo de leche durante el ordeño, sin embargo en cabras no es tan importante esta estimulación previa por el gran volumen de leche almacenado en la cisterna, y que está disponible en elmomentodelordeño(BruckmaieryWellnitz,2008). El proceso de eyección de leche en cabras, en respuesta a la oxitocina, es similar al de vacas yovejas,perolaextraccióndelalecheesdiferentedebidoalamorfologíadelaubre(Bruckmaiery Blum,1998).Encabras,laliberacióndeoxitocinaesaltamentevariableenelmismoanimalyentre diferentes individuos de la misma raza, siendo fácilmente inducida por estimulación táctil previa o por lamáquinadeordeño(BruckmaieryBlum,1998;MarnetyMcKusick,2001).
INTRODUCCIÓN 53 5.2. Efectos de la administración de oxitocina exógena sobre la producción de leche Aunque existen numerosos informes de que la administración exógena de oxitocina en el momento del ordeño puede aumentar la producción de leche, hay contradicciones en la literatura con respecto a sus efectos sobre el rendimiento lechero y calidad de la leche. Éstos se deben principalmenteadiferenciasenlametodologíaydiseñoexperimental,quevandesdeelnúmerodeanimales utilizados, estado de lactación, inyección seguida de remoción de leche o no, inyección administrada conlasubresllenasovacías,ydosisdeoxitocinaadministrada(Lollivierycol.,2002). Laadministracióndedosisintravenosasentre0,1y1UIdeoxitocinapuedeinducirlabajadade la leche en cabras, ya que sólo es necesario rebasar un umbral mínimo de concentración de oxitocina parainiciarelproceso(Schamsycol.,1984).Sinembargo,enlamayoríadelostrabajosexperimentales, losinvestigadoreshanutilizadodosisconcantidadessuprafisiológicas(Lollivierycol.,2002). En vacas, se ha reportado que la administración exógena de oxitocina es una terapia eficaz contralamastitis(Macuhovaycol.,2004).Sinembargonosehanencontradocambiosaparentesen el sistema inmune por los tratamientos con oxitocina, aunque las inyecciones en cantidades suprafisiológicas pueden ayudar en la eliminación de microorganismos patógenos debido a un completo vaciadodelaubre(Werner-Misofycol.,2007).Adicionalmente,algunosestudiosconfirmanunareducción en la eyección espontanea de leche después de retirar los tratamientos crónicos de oxitocina, lo cual puede deberse a una disminución de la oxitocina liberada desde la hipófisis, o por una reducción en la contractibilidad de las células mioepiteliales a niveles fisiológicos de oxitocina en sangre(Bruckmaier,2003). 6. Fraccionamiento lechero En el instante del ordeño, se considera que la leche se encuentra almacenada en la ubre en dos niveles bien diferenciados (fracciones de ubre), o como se obtiene durante una rutina de ordeño completa (fracciones de ordeño).
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 54 6.1. Fracciones de ubre 6.1.1.Lechecisternal Cierta cantidad de leche está contenida en la cisterna o seno glandular. La especial estructuración anatómica de la glándula mamaria del caprino, que incluye la presencia de grandes cisternas(Figura23),permitequebuenapartedelcontenidodelechealmacenadaenelinteriorde laglándulapuedaserevacuadaenformapasiva,esdecir,sinunprocesodecontracción(BruckmaieryBlum,1998). Figura23.Laubrecaprinacanariadestacaporsusgrandescisternas.(U.D.ProducciónAnimalULPGC). 6.1.2.Lechealveolar Una parte de la leche se acumula en los alvéolos y en la red de canales y conductos (Figura24),yestáfijadaporfuerzascapilares.Parasuobtenciónseprecisadelaparticipaciónactiva delanimal,atravésdelapuestaenmarchadelmecanismodeeyeccióndeleche(Bruckmaiery Wellnitz,2008).
INTRODUCCIÓN 55 Figura24.Representacióndelaexpulsióndelalechecontenidaenlosalveolos.(Schmidt,1971). El reparto entre la leche cisternal y alveolar se determinaba mediante el uso de una cánula que seintroducíaporelesfínterdelpezónypermitíaeldrenajedelalechecisternal(PeakeryBlatchford, 1988).Noobstante,estatécnicapuedesobreestimarelvolumendelechecisternal,yaquealgunas razas son muy sensibles a la liberación espontánea de oxitocina endógena, como consecuencia de reflejoscondicionadosalordeñoocomoresultadodelamanipulacióndelpezón.Porello,lasnuevas técnicas incluyen el uso de un antagonista de los receptores de oxitocina para bloquear la eyección espontáneadeleche(Wellnitzycol.,1999). 6.2. Fracciones de ordeño 6.2.1.Lechedemáquina El fraccionamiento obtenido durante el ordeño mecánico permite diferenciar una porción de leche recogida desde la colocación de las pezoneras hasta el cese de flujo de leche sin intervención algunaporpartedelordeñador(Figura25). 6.2.2.Lechedeapuradoamáquina La morfología de ubre de muchas razas caprinas hace necesario realizar un masaje de las regiones cisternales y alzar el ligamento suspensorio por parte del ordeñador, antes de la retirada de laspezoneras,parafavorecerlaremocióndelalechecontenidadebajodelospezones(Figura25).
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 56 6.2.3.Lecheresidual La leche total contenida en la glándula mamaria difícilmente se puede extraer en su totalidad por medios mecánicos o manuales, puesto que una parte sólo puede ser extraída por mecanismos hormonales. Así pues, mediante una inyección de oxitocina se extrae la fracción retenida en el tejido mamario, y aunque no se considera propiamente como una fracción de ordeño, permite expresar el grado de vaciado de la ubre conseguido por medio del ordeño mecánico. Figura25.Fraccióndelechedemáquina(izquierda)ydeapuradoamáquina(derecha).(ICIA). Porconsiguiente,lascabrasconmejoradaptaciónalamáquinadeordeñoseránaquellasque presenten una mayor cantidad de leche de máquina, y menor volumen de leche de apurado y residual, lo que implica una reducción en el tiempo dedicado al ordeño. Sin embargo, en las explotaciones ganaderas,hayunatendenciacentradaenreducirelnúmerodeoperacionesduranteelordeño,omitiendoelapuradoamáquina(McKusickycol.,2003). Porotrolado,sehaseñaladolaimportanciadelamorfologíadeubresobrelasfraccionesde ordeño, destacando la red canalicular, la altura de las cisternas mamarias y el ángulo de inclinación delospezones(LeDu,1985),habiéndoseresaltadotambiénquelasubresglobosassonmásfáciles deordeñarquelasubresdescendidas(Capoteycol.,2006).Además,lafrecuenciadeordeñoafecta especialmente la fracción de apurado a máquina, donde el doble ordeño incrementa significativa-
BIBLIOGRAFÍA 63 KomaraM,BoutinaudM,BenChedlyH,Guinard-FlamentJ,&MarnetP.2009.Once-dailymilking effectsinhigh-yieldingalpinedairygoats.JournalofDairyScience,92:5447–5455. KumeK,PapaL,&HajnoL.2012.EffectsonmilkproductioninF-1crossbredofAlpinegoatbreed (male)andAlbaniangoatbreed(female).ItalianJournalofAnimalScience,11:258–261. LeDuJ.1985.Functionalparametersaffectingtheefficiencyofmilkingmachineadaptedtosheep andgoat.En:Proceedingsofthe36thAnnualMeetingoftheEuropeanAssociationforAnimal Production,Kallithea,Grecia,pp.430–431.EAAP. LeónJ,MacciottaN,GamaL,BarbaC,&DelgadoH.2012.Characterizationofthelactationcurvein Murciano-Granadinadairygoats.SmallRuminantResearch,107:76–84. LollivierV,Guinard-FlamentJ,Ollivier-BousquetsM,&MarnetP.2002.Oxytocinandmilkremoval:two importantsourcesofvariationinmilkproductionandmilkqualityduringandbetweenmilkings. ReproductionNutritionDevelopment,42,173–186. MacuhovaJ,TancinV,&BruckmaierR.2004.Effectsofoxytocinadministrationonoxytocinrelease andmilkejection.JournalofDairyScience,87:1236–1244. MagaE,DaftariP,KueltzD,&PenedoM.2009.Prevalenceofalpha(s1)-caseingenotypesinAmerican dairygoats.JournalofAnimalScience,87:3464–3469. MAGRAMA.2011.MinisteriodeAgriculturaAlimentaciónyMedioAmbiente.http://www.magrama. gob.es. MaltzE,SilanikoveN,&ShkolnikA.1982.EnergycostandwaterrequirementofblackBedouingoats atdifferentlevelsofproduction.TheJournalofAgriculturalScience,98:499–504. ManfrediE,PiacereA,LahayeP,&DucrocqV.2001.GeneticparametersoftypeappraisalinSaanen andAlpinegoats.LivestockProductionScience,70:183–189. ManlongatN,YangT,HinckleyL,BendelR,&KriderH.1998.Physiologic-chemoattractant-inducedmigrationofpolymorphonuclearleukocytesinmilk.ClinicalandVaccineImmunology,5:375–381. MarnetP,&McKusickB.2001.Regulationofmilkejectionandmilkabilityinsmallruminants.Livestock ProductionScience,70:125–133. MartínezA,AcostaJ,Vega-PláJ,&DelgadoJV.2006.Analysisofthegeneticstructureofthecanary goatpopulationsusingmicrosatellites.LivestockScience,102:140–145. MataJ,BermejoL,deNascimentoL,&CamachoA.2010.Theproblemofgrazingplanninginanonequilibrated environment, from the analytical procedure toward the system approach. Small RuminantResearch,89:91–101. McDougallS,AnnissFM,&CullumA.2002.Effectoftransportstressonsomaticcellcountsindairy goats.ProceedingsoftheNewZealandofAnimalProduction,62:16–18.
BIBLIOGRAFÍA 64 McKusickBC,ThomasDL,&BergerYM.2003.EffectofomissionofmachinestrippingonmilkproductionandparlorthroughputinEastFriesiandairyewes.JournalofDairyScience,86:680–687. MehdidA,DíazJR,MartíA,VidalG,&PerisC.2013.Effectofestrussynchronizationondailysomatic cell count variation in goats according to lactation number and udder health status. Journal of DairyScience,96:4368–4374. MinB,HartS,SahluT,&SatterL.2005.Theeffectofdietsonmilkproductionandcomposition,andon lactationcurvesinpastureddairygoats.JournalofDairyScience,88:2604–2615. MocquotJC,&AuranT.1974.Effetsdedifférentesfréquencesdetraitesurlaproductionlaitièredes caprins.AnnalesdeGénétiqueetdeSélectionAnimale,6:463–476. MiocB,PrpicZ,VnucecI,BaracZ,SusicV,SamarzijaD,&PavicV.2008.Factorsaffectinggoatmilk yieldandcomposition.Mljekarstvo,58:305–313. MontaldoH,AlmanzaA,&JuárezA.1997.Geneticgroup,ageandseasoneffectsonlactationcurve shapeingoats.SmallRuminantResearch,24:195–202. Morand-FehrP,BlanchartG,LeMensP,RemeufF,SauvantD,LenoirJ,LamberetG,LeJauoen,JC,& BasP.1986.Donnéerecentessurlacompositiondulaitdechévre.JournéesdelaRecherche OvineetCaprine,11:253–298. Morand-FehrP,FedeleV,DecandiaM,&LeFrileuxY.2007.Influenceoffarmingandfeedingsystems oncompositionandqualityofgoatandsheepmilk.SmallRuminantResearch,68:20–34. MowlenA.2005.MarketinggoatdairyproduceintheUK.SmallRuminantResearch,60:207–213. PaapeM,WiggansG,BannermanD,ThomasD,SandersA,ContrerasA,MoroniP,&Miller,R.2007. Monitoringgoatandsheepmilksomaticcellcounts.SmallRuminantResearch,68:114–125. ParkY.2006.Goatmilk—chemistryandnutrition.En:HandbookofMilkofNon-bovineMammals.Park Y,&HaenleinG.(Eds.)BlackwellPublishing,Oxford,UK,34–58. ParkY.2007.Rheologicalcharacterisiticsofgoatandsheepmilk.SmallRuminantResearch,68:73–87. ParkY,JuárezM,RamosM,&HaenleinG.2007.Physico-chemicalcharacteristicsofgoatandsheep milk.SmallRuminantResearch,68:88–113. ParkY,&HaenleinG.2010.Milkproduction.En:GoatScienceandProduction.SolaimanS.(Ed.)BlackwellPublishing,Iowa,USA,275-292. PeakerM,&BlatchfordD.1988.Distributionofmilkinthegoatmammaryglandanditsrelationtothe rateandcontrolofmilksecretion.JournalofDairyResearch,55:41–48. PerisS.1994.Característicasdelacurvadelactaciónyaptitudalordeñomecánicodelacabra derazaMurciano-Granadina.TesisDoctoral.UniversidadAutónomadeBarcelona,España,149pp.
BIBLIOGRAFÍA 65 PerisS,CajaC,SuchX,CasalsR,FerretA,&TorreC.1997.InfluenceofkidrearingsystemsonmilkcompositionandyieldofMurciano-Granadinadairygoats.JournalofDairyScience,80:3249–3255. PerisS,CajaG,&SuchX.1999.RelationshipsbetweenudderandmilkingtraitsinMurciano-Granadinadairygoats.SmallRuminantResearch,33:171–179. PirisiA,LauretA,&DubeufJ.2007.Basicandincentivepaymentsforgoatandsheepmilkinrelation toquality.SmallRuminantResearch,68:167–178. PulinaG,NuddaA,&BattaconeG.2008.Nutritionandqualityofgoat’smilk.En:DairyGoatsFeeding andNutrition.PulinaG,&CannasA.(Eds.)CABInternational,Bolonia,Italia,1–30. RamírezM.2009.Guíadelosquesosespañoles.PublicacionesTécnicasAlimentarias,Madrid,España,253pp. RancourtM,FoisN,LavínM,TchakérianE,&VallerandF.2006.Mediterraneansheepandgoatsproduction:Anuncertainfuture.SmallRuminantResearch,62:167–179. Raynal-LjutovacK,PirisiA,deCrémouxR,&GonzaloC.2007.Somaticcellsofgoatandsheepmilk: Analytical,sanitary,productiveandtechnologicalaspects.SmallRuminantResearch,68:126– 144. RibeiroA,&RibeiroS.2010.Specialtyproductsmadefromgoatmilk.SmallRuminantResearch,89: 225–233. Romero-HuelvaM,Ramos-MoralesE,&Molina-AlcaideE.2012.Nutrientutilization,ruminalfermentation,microbialabundances,andmilkyieldandcompositionindairygoatsfeddietsincluding tomatoandcucumberwastefruits.JournalofDairyScience,10:6015–6026. RovaiM.2001.Caracteresmorfológicosyfisiológicosqueafectanlaaptitudalordeñomecánicoen ovejasderazaManchegayLacaune.TesisDoctoral.UniversidadAutónomadeBarcelona, España,281pp. SalamaA.2005.Modifyingthelactationcurveindairygoats:Effectsofmilkingfrequency,dryperiod, andkiddinginterval.TesisDoctoral.UniversidadAutónomadeBarcelona,España,142pp. SalamaA,SuchX,CajaG,RovaiM,CasalsR,AlbanellE,MarínMP,&MartíA.2003.Effectsofonce versustwicedailymilkingthroughoutlactationonmilkyieldandmilkcompositionindairy goats.JournalofDairyScience,86:1673–1680. SalamaA,CajaG,SuchX,PerisS,SorensenA,&KnightC.2004.Changesincisternaluddercompartmentinducedbymilkingintervalindairygoatsmilkedonceortwicedaily.JournalofDairy Science,87:1181–1187. Sánchez-MacíasD,Morales-delaNuezA,Moreno-IndiasI,Hernández-CastellanoL,Mendoza-Grimón V,CastroN,&ArgüelloA.2011.Lipolysisandproteolysisprofilesoffreshartisanalgoatcheese madewithrawmilkwith3differentfatcontents.JournalofDairyScience,94:5786–5793.
BIBLIOGRAFÍA 66 SandovalJ.2003.TratadodeAnatomíaVeterinaria,TomoIV.ImprentaSorbes,León,España.281pp. Sanogo S, Shaker M, Nantoumé H, & Salem AF. 2012. Milk yield and composition of crossbred Sahelian×Anglo-Nubiangoatsinthesemi-intensivesysteminMaliduringthepreweaningperiod.TropicalAnimalHealthandProduction,45:305–310. SanzSampelayoM,ChilliardY,SchmidelyP,&BozaJ.2007.Influenceoftypeofdietonthefatconstituentsofgoatandsheepmilk.SmallRuminantResearch,68:42–63. SchamsD,MayerH,ProkoppA,&WorstorffH.1984.Oxytocinsecretionduringmilkingindairycows withregardtothevariationandimportanceofathresholdlevelformilkremoval.Journalof Endocrinology,102:337–343. SchmidtGH.1971.Biologyoflactation.WH.FreemanandCompany,SanFrancisco,USA,317pp. ScolozziC,MartiniM,&AbramoF.2003.Amethodforidentificationandcharacterizationofewe’smilk fatglobules.Milchwissenschaft,58:490–493. SilanikoveN.2000a.Effectsofheatstressonthewelfareofextensivelymanageddomesticruminants. LivestockProductionScience,67:1–18. SilanikoveN.2000b.Thephysiologicalbasisofadaptationingoatstoharshenviroments.SmallRuminantResarch,35:181–193. SilanikoveN,LeitnerG,MerinU,&ProsserC.2010.Recentadvancesinexploitinggoat’smilk:Quality, safetyandproductionaspects.SmallRuminantResearch,89:110–124. SinapisE,HatziminaoglouaI,MarnetP,AbasZ,&BolouA.2000.Influenceofvacuumlevel,pulsation rateandpulsatorratioonmachinemilkingefficiencyinlocalGreekgoats.LivestockProductionScience,64:175–181. SoryalK,ZengS,MinB,&HartS.2004.EffectoffeedingtreatmentsandlactationstagesoncompositionandorganolepticqualityofgoatmilkDomiaticheese.SmallRuminantResearch,52: 109–116. Suárez-TrujilloA,CapoteJ,ArgüelloA,CastroN,Morales-delaNuezA,TorresA,MoralesJ,&Rivero M.2013.Effectsofbreedandmilkingfrequencyonudderhistologicalstructuresindairygoats. JournalofAppliedAnimalResearch,41:166–172. TorresA,&CapoteJ.2011.Venezuelaylascabrascanarias.RevistaAgropalca,15:25. Tziboula-ClarkeA.2003.Goatmilk.En:EncyclopediaofDairySciences.RoginskiH,&FuquayJ.(Eds.) AcademicPress,Cornwall,UK,1270–1279. ValentiB,PaganoR,&AvondoM.2012.EffectofdietatdifferentenergylevelsonmilkcaseincompositionofGirgentanagoatsdifferinginCSN1S1genotype.SmallRuminantResearch,105: 135–139.
BIBLIOGRAFÍA 67 VigneJ,&HelmerD.2006.Wasmilka“secondaryproduct”intheOldWorldNeolithisationprocess? Itsroleinthedomesticationofcattle,sheepandgoats.Anthropozoologica,42:9–40. WangP.1989.UddercharacteristicsinToggenburgdairygoats.SmallRuminantResearch,2:181–190. WellnitzO,BruckmaierR,AlbrechtC,&BlumJ.(1999).Atosiban,anoxytocinreceptorblocking agent:Pharmacokineticsandinhibitionofmilkejectionindairycows.JournalofDairyResearch,66:1–8. Werner-MisofC,PfafflM,MeyerH,&BruckmaierR.2007.Theeffectofchronicoxytocin-treatmenton thebovinemammaryglandimmunesystem.VeterinarniMedicina,11:475–486. WildeC,&KnightC.1990.Milkyieldandmammaryfunctioningoatsduringandafteronce-dailymilking.JournalofDairyResearch,57:441–447. ZahraddeenD,ButswastI.,&MbapS.2009.Anoteonfactorsinfluencingmilkyieldoflocalgoatsundersemi-intensivesysteminSudansavannahecologicalzoneofNigeria.LivestockResearch forRuralDevelopment,21:34–37. ZengS,&EscobarE.1995.Effectofparityandmilkproductiononsomaticcellcount,standardplate countandcompositionofgoatmilk.SmallRuminantResearch,17:269–274. ZengS,&EscobarE.1996.Effectofbreedandmilkingmethodonsomaticcellcount,standardplate countandcompositionofgoatmilk.SmallRuminantResearch,19:169–175. ZengS,EscobarE,&PophamT.1997.Dailyvariationsinsomaticcellcount,composition,andproductionofAlpinegoatmilk.SmallRuminantResearch,26:253–260. ZengS,ZhangL,WiggansG,ClayJ,LacroixR,&WangJG.2008.Currentstatusofcompositionand somaticcellcountinmilkofgoatsenrolledinDairyHerdImprovementProgramintheUnited States.En:NewResearchonLivestockScienceandDairyFarming.DiAlbertoP,&CostaC. (Eds.)NovaSciencePublisher,NewYork,USA,129–144. ZygoyiannisD.1994.Anoteontheeffectofnumberandgenotypeofkidsonmilkyieldandcomposition ofindigenousGreekgoats(CapraPrisca).AnimalProduction,58:423–426.
ARTÍCULO 1
ARTÍCULO 1 71 1071 J. Dairy Sci. 96 :1071–1074 http://dx.doi.org/ 10.3168/jds.2012-5435 © American Dairy Science Association®, 2013 . ABSTRACT Thirty-six dairy goats of 3 breeds (Majorera, Tinerfeña, and Palmera) in mid lactation (124 ± 8 d in milk) were subjected unilaterally to once (×1) or twice daily milking (×2) for 5 wk to evaluate udder morphology, milk partitioning, and somatic cell count. Majorera and Palmera goats presented the highest and lowest udder depth values, respectively, whereas the differences between initial and final cistern-floor and teat-floor distances were not affected by milking frequency or breed factors. Cisternal and alveolar milk percentages were similar between ×1 and ×2 in the studied breeds. Milking frequency did not affect milk composition in the cisternal fraction, suggesting a greater transfer of milk from the alveoli to the cistern during early udder filling. However, milking frequency caused diverse changes in the milk composition in the alveolar fraction, especially in fat, lactose, and total solids contents. No udder halves presented clinical mastitis during the experimental period, suggesting that ×1 does not impair udder health and indicating that the studied breeds are adapted to this milking frequency. Key words: milking frequency , milk partitioning , milk quality , dairy goat Short Communication Intramammary filling rate and cisternal capacity to store milk determine the choice of an adequate milking routine. Overfilling of the udder increases intramammary pressure and distention of the alveoli, which can compromise subsequent milk synthesis as has been reported by Peaker (1980). Animals with large cisterns are milked faster with simplified routines and are better at tolerating extended milking intervals (Knight and Dewhurst, 1994; Ayadi et al., 2003; Salama et al., 2003). Techniques for determining cisternal and alveolar milk fractions have been improved and include the use of an oxytocin receptor antagonist to block spontaneous milk ejection (Wellnitz et al., 1999), allowing a reliable separation between both fractions. This is important because the udder morphology of some dairy goat breeds (e.g., Tinerfeña breed) is characterized by higher teat-floor distance (TF) than cistern-floor distance (CF), a negative circumstance that makes more difficult the emptying of cisternal milk by gravity (López et al., 1999). The aim of the present study was to determine the effects of milking frequency on udder morphology, milk partitioning, composition of each fraction, and SCC of 3 dairy goat breeds (Majorera, Tinerfeña, and Palmera). The present study was performed on the experimental farm of the Instituto Canario de Investigaciones Agrarias in Tenerife (Spain) on 36 dairy goats belonging to 3 different breeds: Majorera (n = 12), Tinerfeña (n = 12), and Palmera (n = 12). The experimental animal procedures were approved by the Ethical Committee of the Universidad de Las Palmas de Gran Canaria (Arucas, Spain). Goats with symmetrical udder halves were in third parity with 124 ± 8 DIM at the beginning of the experiment. The milking frequency before the start of the experimental period was once per day. During a 5-wk period, each goat was milked once daily in the left mammary gland (×1; at 0700 h), whereas the right mammary gland was milked twice daily (×2; at 0700 and 1700 h). The animals were fed with commercial concentrate, maize, lucerne, wheat straw, and a vitamin-mineral corrector in accordance with the guidelines issued for lactating goats by Institut National de la Recherche Agronomique (INRA, Paris, France; Jarrige, 1990). Goats were milked in a double 12-stall parallel milking parlor (Alfa Laval Iberia SA, Madrid, Spain) equipped with recording jars (4 L ± 5%) and a low-line milk pipeline. Milking was performed at a vacuum pressure of 42 kPa, a pulsation rate of 90 pulses/min, and a pulsation ratio of 60/40, in accordance with Capote et al. (2006). The milking routine included wiping dirt off teat ends and stripping 2 to 3 squirts of milk from each teat; machine milking and stripping milking, done by the operator to remove the milk remaining in the udder before cluster removal; and teat dipping in an Short communication: Effects of milking frequency on udder morphology, milk partitioning, and milk quality in 3 dairy goat breeds A. Torres ,* N. Castro ,† L. E. Hernández-Castellano ,† A. Argüello ,†1 and J. Capote * * Instituto Canario de Investigaciones Agrarias, La Laguna, Tenerife 38200, Spain † Department of Animal Science, Universidad de Las Palmas de Gran Canaria, 35413 Arucas, Spain Received February 15, 2012. Accepted October 26, 2012. 1 Corresponding author: [email protected]
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 72 1072 TORRES ET AL. Journal of Dairy Science Vol. 96 No. 2, 2013 iodine solution (P3-cide plus; Henkel Hygiene, Barcelona, Spain). Milk recording and sampling were done at wk 1, 3, and 5. Before the experiment, the goats were exposed to 3 wk of adaptation. In the first and second weeks, the goats began to enter the milking parlor in the afternoon, but the goats were not milked. During the third week of adaptation, the goats were milked once and twice daily in the left and right mammary gland, respectively, but the milk was not collected. Udder measurements of each goat were taken just before the first and the last milking of the experimental period. The following udder measurements were performed: CF and TF, recorded as the differences between initial and final measurements (ΔCF and ΔTF), and udder depth (UD), recorded as the difference in distance between the udder floor and the cistern floor. Before the a.m. milking (24and 14-h milking intervals for ×1 and ×2, respectively) on the sampling days, each goat was injected intravenously with 0.8 mg of an oxytocin receptor blocking agent (Tractocile; Ferring SAU, Madrid, Spain) inside a pen immediately before entering the parlor to record cisternal milk volume. After cisternal milk removal, the goats were injected intravenously with 2 IU of oxytocin (Oxiton; Laboratorios Ovejero, León, Spain) to reestablish milk ejection to allow the measurement of alveolar milk. Cisternal and alveolar milk volumes were recorded by using the recording jars in the milking parlor and milk samples were collected separately for each udder half and fraction. Milk samples (cisternal and alveolar fractions) were analyzed immediately after collection to determine milk composition and SCC. Protein, fat, lactose, TS, and SNF percentages were determined using a MilkoScan 133 analyzer (Foss Electric A/S, Hillerød, Denmark), and SCC using a Fossomatic 90 cell counter (Foss Electric A/S). Somatic cell count was calculated by a weighted average of the cisternal and alveolar SCC. The statistical analysis used to evaluate the effects of breed and milking frequency on morphological parameters of udder, milk partitioning and SCC was PROC MIXED of SAS (version 9.0; SAS Institute Inc., Cary, NC). The model included fixed effects of milking frequency (×1 or ×2) and breed (Majorera, Tinerfeña, or Palmera) and their interactions. The repeated statement was used to take into account repeated measures for each individual animal. Differences among the breeds and milking frequencies were evaluated using a multiple comparison test following the Tukey-Kramer method. Statistical differences were considered significant at P < 0.05. Data are presented as least squares means. The ΔCF and ΔTF (Table 1) did not differ due to milking frequency or breed (P > 0.05). Knight and Dewhurst (1994) found that large cisternal size may explain the small negative effects of longer milking intervals on udder morphology because it is better prepared to accommodate greater milk accumulation, and may explain the absence of differences in the cistern descent of goat udders. Majorera and Palmera goats presented the highest and lowest UD values, respectively (Table 1). The increase in UD values during the experimental period can be explained because ΔTF were lower than ΔCF, which implies that increasing the cistern depth increases the UD. The cistern depth is a consequence of teat placement of the studied goats whose teats are not located in the ventral portion of the udder (Capote et al., 2006). Cisternal and alveolar milk percentages were similar between ×1 (24 h after milking) and ×2 (14 h after milking) in Majorera, Tinerfeña, and Palmera breeds (Table 1). Salama et al. (2004) did not find differences in cisternal milk fraction in Murciano-Granadina goats between ×1 and ×2 when milking intervals were 16 and 24 h (values ranged from 66 to 76%). The differences observed in the cisternal and alveolar fractions between breeds may be explained by the cisternal size, because greater cisterns are able to store more milk. Bruckmaier et al. (1997) explained that a large absolute cisternal volume implies that a large fraction of the milk is stored within the cisternal cavities and it varies according to breed. Percentages of cisternal milk components (Table 1) were not affected by milking frequency (P > 0.05). This absence of differences between ×1 and ×2 goats might be due to the fact that approximately 80% of total milk was stored in the cisternal compartment and most of the transfer of milk from the alveoli and small milk ducts had already taken place. However, McKusick et al. (2002) observed marked differences in milk fat percentage in the cisternal fraction between different milking intervals in dairy ewes, in which the cistern was only capable of storing approximately 50% of the total milk volume, being more susceptible to changes in the transfer of milk components. Alveolar milk of ×1 goats contained higher percentages of fat and TS than alveolar milk of ×2 goats, but these differences were significant only in the Majorera breed. McKusick et al. (2002) explained that a transfer of milk fat from the alveoli to the cistern occurs during early udder filling; however, this transfer no longer takes place during later intervals, resulting in an accumulation of milk fat in the alveolar compartment. Alveolar milk was richer in fat content than cisternal milk in all breeds and milking intervals, which agrees
ARTÍCULO 2 79 Please cite this article in press as: Torres, A., et al., Comparison between two milk distribution structures in dairy goats milked at different milking frequencies. Small Ruminant Res. (2013), http://dx.doi.org/10.1016/j.smallrumres.2013.04.013 ARTICLE IN PRESS GModel RUMIN-4519; No.of Pages6 A. Torres et al. / Small Ruminant Research xxx (2013) xxx–xxx 3 Table 1 Milk yield, milk composition and milk component yield of each udder half of three dairy goat breeds milked once (X1) or twice (X2) daily.a Parameter Goat breed SEM Majorera Tinerfe˜ na Palmera X1 X2 X1 X2 X1 X2 Milk yield (L/d) 1.39ab 1.51a1.27ab 1.31ab 1.04c1.19b0.049 FCMb(L/d) 1.34a1.50a1.21ab 1.28a1.05b1.24a0.045 Fat (%) 3.79b3.94b3.76b3.88b4.06ab 4.29a0.060 Protein (%) 3.67bc 3.59c3.63bc 3.51c3.92a3.72b0.041 Lactose (%) 4.83 4.86 4.85 4.83 4.78 4.81 0.028 Total solids (%) 12.99b13.06b12.92b12.91b13.58a13.53a0.083 Fat (g/d) 52.47a59.42a46.90ab 50.00ab 41.77b50.98a1.785 Protein (g/d) 50.95a54.40a44.78ab 44.73ab 40.79b44.45ab 1.504 Lactose (g/d) 67.20ab 73.65a61.70ab 64.22ab 49.96c57.48b2.513 Total solids (g/d) 180.42a197.58a162.07ab 168.04a141.01b161.42a5.936 a–cMeans with different superscripts within the same row are different (P< 0.05). aData are least squares means and standard error of means. bFCM = total milk yield (L/d) ×(0.400 + 0.150 ×total fat content (%)). Majorera and Tinerfe˜ na goats were not different in milk component yields between X1 and X2 (Table 1). In contrast, Palmera goats had significant increases by 22%, 15%, and 14% in X2 daily yields of fat, lactose and total solids, respectively, compared with X1. However, protein yield did not significantly increase as did the other milk components. CM and AM percentages (Table 2) did not differ due to milking frequency in the studied breeds (P> 0.05). Majorera and Palmera had the highest and lowest CM percentages, respectively, both in X1 and X2 (P< 0.05). In the same way, MM and MSM percentages (Table 2) were not affected by milking frequency in Tinerfe˜ na and Palmera breeds (P> 0.05). However, Majorera goats had higher and lower values in MM and MSM fractions, respectively, in X1 with regardto X2. RM percentages were not affected by the milking frequency and breed factors (P> 0.05), ranging from 10.66 to 14.49% in the studied conditions. Correlation coefficients among milk fractions are reported in Table 3. High negative correlations between MM and MSM fractions (P< 0.05) were observed for X1 (Majorera, r=−0.76; Tinerfe˜ na, r=−0.94; Palmera, r=−0.90) and X2 (Majorera, r=−0.72; Tinerfe˜ na, r=−0.70; Palmera, r=−0.90). Moreover, MM and RM were only significantly correlated for X1 (Majorera, r=−0.82; Tinerfe˜ na, r=−0.93; Palmera, r=−0.86). In addition, no significant correlation coefficients were found between MSM and RM for X1 and X2. Finally, CM and AM were not correlated with MM, MSM and RM fractions in the studied breeds milked at X1 and X2 (P> 0.05). 4. Discussion The increase in milk yield in Palmera goats was higher than the values reported in Tinerfe˜ na goats (6%) by Capote et al. (1999) and Damascus goats (7%) by Papachristoforou et al. (1982) and similar to loss caused by X1 in Alpine goats (16%) by Komara et al. (2009). The increase in FCM in Palmera goats was comparable with the FCM value reported in Murciano-Granadina goats (18%) by Salama et al. (2003). However, the goats of those studies were milked with the same frequency in both glands. The unilateral milking frequency effect indicates that the increase in milk yield is a response strictly at the level of the mammary gland via local factors, and not due to the greater availability of nutrient supply caused by the suppression of milking in the opposite gland (Nudda et al., 2002; Wall and McFadden, 2008). Table 2 Milk fractions of three dairy goat breeds milked once (X1) or twice (X2) daily.a,b FractioncGoat breed SEM Majorera Tinerfe˜ na Palmera X1 X2 X1 X2 X1 X2 CM (%) 82.28a81.75a80.12ab 80.30ab 77.22bc 76.70c0.528 AM (%) 18.41c18.77c20.15bc 19.99bc 23.02ab 23.43a0.498 MM (%) 77.29a71.66b67.21bc 61.21c65.86bc 59.07c1.366 MSM (%) 12.67c17.41b19.71b24.94ab 22.34ab 27.57a1.100 RM (%) 10.66 11.61 12.96 14.49 12.48 13.24 0.449 a–cMeans with different superscripts within the same row are different (P< 0.05). aData are least square means and standard error of means. bMilk fractions were measured at 24and 14-h milking intervals for X1 and X2 goats, respectively. cCM, cisternal milk; AM, alveolar milk; MM, machine milk; MSM, machine stripping milk; RM, residual milk.
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 80 Please cite this article in press as: Torres, A., et al., Comparison between two milk distribution structures in dairy goats milked at different milking frequencies. Small Ruminant Res. (2013), http://dx.doi.org/10.1016/j.smallrumres.2013.04.013 ARTICLE IN PRESS GModel RUMIN-4519; No.of Pages6 4A. Torres et al. / Small Ruminant Research xxx (2013) xxx–xxx Table 3 Pearson’s correlation coefficients matrix among milk fractions of three dairy goat breeds milked once (above diagonal) or twice (below diagonal) daily. Breed Fractiona CM AM MM MSM RM CM Majorera −0.885*−0.285 0.379 0.181 Tinerfe˜ na −0.989*0.084 −0.050 −0.159 Palmera −0.987*−0.051 0.162 0.007 AM Majorera −0.892*−0.007 −0.245 0.173 Tinerfe˜ na −0.935*−0.189 0.143 0.232 Palmera −0.990*0.008 −0.136 0.023 MM Majorera 0.411 −0.550 −0.761*−0.823* Tinerfe˜ na 0.067 −0.082 −0.941*−0.933* Palmera 0.617 −0.586 −0.897*−0.863* MSM Majorera −0.164 0.314 −0.721*0.139 Tinerfe˜ na 0.158 −0.210 −0.702*0.694 Palmera −0.615 0.636 −0.895*0.666 RM Majorera 0.128 0.053 −0.050 −0.258 Tinerfe˜ na −0.476 0.433 −0.253 −0.107 Palmera 0.024 −0.107 −0.406 0.006 *P< 0.05. aCM, cisternal milk; AM, alveolar milk; MM, machine milk; MSM, machine stripping milk; RM, residual milk. The differences observed in milk yield in Majorera, Tinerfe˜ na and Palmera goats between X1 and X2 may be explained as a consequence of cisternal capacity of each breed (Bruckmaier and Blum, 1998). A large voluminous cistern takes more time in filling up, delaying the effects of the intramammary feedback inhibitor, intramammary pressure, or tight junction integrity on milk transference from the alveoli to the cisterns, during the filling of the udder (Capote et al., 2008). Recently, serotonin has been proposed as a feedback inhibitor of lactation, being a component involved in milk regulation (Hernandez et al., 2008). However, milk yields did not differ between treatment and control halves, which suggest that serotonin is not a local factor. In addition, Silanikove et al. (2000) showed in goats and cows that the plasmin-induced -casein f(1–28) peptide can serve as a local regulator on milk secretion by functioning as a potassium channel blocker, which was subsequently confirmed in dairy cows by Silanikove et al. (2009). It is predicted that for milking intervals of less than 20 h in goats and 18 h in cows, the concentration of caseinderived peptides, including the active component -casein f(1–28), would be higher in the cistern than in the alveoli; therefore, the alveoli will not be exposed to the full impact of the negative feedback signal of this peptide. Extending milk stasis beyond these times exceeds the storage capacity of the cistern, resulting in the equilibration of -casein f(1–28) concentration between the cistern and the alveoli (Silanikove et al., 2010). Thus, animals with smaller udder size, and hence of cisternal compartment, such as Palmera goats (SuárezTrujillo et al., 2013; Torres et al., 2013), are more affected by mechanisms of feedback inhibition. Silanikove et al. (2010) explained that high milk producing goats, as Saanen, selected to high alveolar to cistern compartment ratio, are the most sensitive to changes in milking frequency. In contrast, medium milk producing goats, as some Spanish breeds, may attain their genetic potential for milk yield in X1 regimen due to selection for high cistern capacity. The physiological explanation relates to the suggestion that - casein f(1–28) is effective only in the alveoli where it is in contact with the epithelial cells. Exposing the alveoli to high concentration of -casein f(1–28) will induce disruption of the tight junction (Silanikove et al., 2010). Milk fat content was not affected by milking frequency which is in accordance with Komara et al. (2009), who also did not observe differences in fat globule size between X1 and X2 for Alpine goats. However, Salama et al. (2003) showed that milk of X1 goats had a 10% more fat content than milk of X2 goats. Milk fat is considered to be the most variable component in ruminant milk, due to differing regulatory mechanisms for secretion of milk fat globules relative to the components in the aqueous phase of milk and to the transfer between alveolar and cisternal compartments (Salama et al., 2003). X1 management in high-yielding goats is a potent stressor that is able to disturb alveolar milk ejection because alveolar milk was shown to contain up to 75% of milk fat when milk ejection was inhibited (Labussière, 1988). However, the absence of significant differences in the studied breeds might be due to the fact that approximately 80% of total milk was stored in the cisternal compartment and most of the transfer of milk fat from the alveoli to the cistern had already taken place. Milk protein concentration was significantly higher in X1 than in X2 udder halves in Palmera goats, which agrees with observations in dairy goats by Komara et al. (2009) and dairy ewes by Nudda et al. (2002).Salama et al. (2003) explained that the concentration effect of the protein in X1 with respect to X2 was due to the milk volume, this was lower with X1 but the casein synthesized remained and became more concentrated in the milk. In goats, Capote et al. (1999) found that milking frequency did not affect lactose percentage and reiterate the assertion that lactose is the milk component least influenced by breed and milking factors, indicating a similar
ARTÍCULO 2 81 Please cite this article in press as: Torres, A., et al., Comparison between two milk distribution structures in dairy goats milked at different milking frequencies. Small Ruminant Res. (2013), http://dx.doi.org/10.1016/j.smallrumres.2013.04.013 ARTICLE IN PRESS GModel RUMIN-4519; No.of Pages6 A. Torres et al. / Small Ruminant Research xxx (2013) xxx–xxx 5 performance of the synthetic activity of the mammary gland. In the studied breeds there were no significant differences found in total solids content between X1 and X2. There is disagreement about the milking frequency effects on total solids percentages. Capote et al. (1999) had observed a lower total solids fraction in X1 (12.48%) than X2 (12.84%), while for Salama et al. (2003) the total solids were higher in X1 (13.60%) than X2 (12.90%) in goats during an entire lactation. Finally, the fact that Palmera goats had higher percentages of total solids than Majorera and Tinerfe˜ na both in X1 and X2, may be explained because the Palmera had higher percentages of fat and protein than the other two breeds. The increases in fat, lactose, and total solids yields were consistent with the significant increase in the milk production of Palmera goats. However, the absence of differences in protein yield between X1 and X2 can be explained by a lower concentration of protein in X2, suggesting that cheese yield could not be maintained. Marnet and Komara (2008) explained that the regulation of milk components synthesis is dependent on the duration of the milking interval, which can influence cheese-making capacity and cheese quality. Despite the differences in milk yield in Palmera goats between X1 and X2, there were not differences in the distribution of milk in the udder. Salama et al. (2004) did not find differences in milk accumulation rates in the cisternal compartment at 16 and 24 h in Murciano-Granadina goats milked X1 or X2, whereas Torres et al. (2013) suggested that the high percentages of milk stored in cisternal compartments for 14and 24-h milking intervals may be explained by a greater transfer of milk from the alveoli to the cisterns during early udder filling. The differences in milk partitioning among breeds were due to the cisternal size of each breed that influences the capacity to store milk in this compartment. For example, Rovai et al. (2008) found CM–AM ratio of 59–41 and 77–23 for Manchega and Lacaune ewes, respectively, where Lacaune breed presented a greater cisternal area than Manchega breed (24.0 vs. 12.4 cm2). MM and MSM percentages were higher and lower, respectively, in X1 udder halves in the studied breeds, but the differences were significant only in Majorera goats. Previously, Capote et al. (2009) found no differences in MM percentages between X1 (67.8%) and X2 (64.5%) in Tinerfe˜ na goats of high milk production, while MSM percentages were higher in X2 (27.8%) than X1 (20.7%), and RM percentages were higher in X1 (11.5%) than X2 (7.7%), suggesting that an increase in milking frequency in a normal routine implies greater stimulation and thus a higher milk drop to the cisterns. Moreover, Majorera goats had a higher and lower MM and MSM percentages, respectively, than Tinerfe˜ na and Palmera goats. Caja et al. (1999) explained that quantities of milk in each partition obtained by mechanical milking depend on the udder morphology and the development of cisternal and canalicular systems; which suggests a high variability between breeds and even between animals of same breed. RM percentages were not affected by the breed, and they were similar than those reported in Murciano-Granadina (9–11%; Peris et al., 1996) and Tinerfe˜ na (7–12%; Capote et al., 2009) goats. In addition, Marnet and McKusick (2001) reported significant increases in MSM percentage without proportional modification of AM or CM volume in Lacaune ewes between the years 1982 and 1992. The increase in MSM fraction was a consequence of the tendency to have more horizontally placed teats in the udder which increases cisternal storage capacity to improve milk production (Bruckmaier et al., 1997; Marnet and McKusick, 2001). High negative correlations observed between MM and MSM fractions both in X1 and X2 in the studied breeds differs with these observed by Peris et al. (1996) and Caja et al. (1999) who did not find significant correlations between both fractions. However, it is clear that the correlation between both them could help in the selection of goats to improve the milkability. Furthermore, Peris et al. (1996) noted that the negative correlation between MM and RM in goats could reduce the milking time because they accumulate more milk into the cisterns. Although, CM and AM (Salama et al., 2004) or MM, MSM and RM percentages (Capote et al., 2008) have a strong dependence on udder morphology, the absence of significant correlation coefficients between CM and AM with MM, MSM, and RM fractions impeded the establishment of a relationship between both milk partitioning structures, at least in goat udders that have a more horizontal teat insertion. 5. Conclusion The results demonstrated that X2 practice did not improve the milk production of the Majorera and Tinerfe˜ na breeds, so it is a consequence of the adaptation of these breeds to X1, which is an interesting issue in goat production systems, because it requires fewer variable costs. Nevertheless, the high increase in milk yield in the Palmera goats due to X2 could seem a profitable management at certain times during the lactation. However, this practice did not produce an increased in milk protein yield in accordance with milk yield. Therefore, other studies are required to evaluate how the milking frequency affects the cheese yield, which is a very important part of the Canary Islands livestock economy. Additionally, the knowledge of the structures of milk partitioning can serve as a basis for future selection programs to improve the milkability of the studied breeds. Furthermore, if a wider selection of breeds could be studied, ranging from low milk yielding to high milk yielding breeds, the relationship among milk fractions would be more noticeable. Conflict of interest None. Acknowledgment This work was supported by Fondo Europeo de Desarrollo Regional-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (FEDER-INIA) RTA200900125.
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 82 Please cite this article in press as: Torres, A., et al., Comparison between two milk distribution structures in dairy goats milked at different milking frequencies. Small Ruminant Res. (2013), http://dx.doi.org/10.1016/j.smallrumres.2013.04.013 ARTICLE IN PRESS GModel RUMIN-4519; No.of Pages6 6A. Torres et al. / Small Ruminant Research xxx (2013) xxx–xxx References Bruckmaier, R.M., Paul, G., Mayer, H., Schams, D., 1997. Machine milking of Ostfriesian and Lacaune dairy sheep: udder anatomy, milk ejection and milking characteristics. J. Dairy Res. 64, 163–172. Bruckmaier, R.M., Blum, J.W., 1998. Oxytocin release and milk removal in ruminants. J. Dairy Sci. 81, 939–949. Caja, G., Capote, J., López, J.L., Peris, S., Such, X., Argüello, A., 1999. Milk partitioning and milk flow rate of Canarian dairy goats under once daily or twice daily milking frequencies. In: Barillet, F., Zervas, N.P. (Eds.), Milking and Milk Production of Dairy Sheep and Goats. Wageningen Pers, Wageningen, pp. 274–280. Capote, J., López, J.L., Caja, G., Peris, S., Argüello, A., Darmanin, N., 1999. The effects of milking once or twice daily throughout lactation on milk production of Canarian dairy goats. In: Barillet, F., Zervas, N.P. (Eds.), Milking and Milk Production of Dairy Sheep and Goats. Wageningen Pers, Wageningen, pp. 267–273. Capote, J., Castro, N., Caja, G., Fernández, G., Briggs, H., Argüello, A., 2008. Effectsofthefrequency of milking and lactationstageonmilk fractions and milk composition in Tinerfe˜ na dairy goats. Small Rumin. Res. 75, 252–255. Capote, J., Castro, N., Caja, G., Fernández, G., Morales-delaNuez, A., Argüello, A., 2009. The effects of the milking frequency and milk production levels on milk partitioning in Tinerfe˜ na dairy goats. Milchwissenschaft 64, 239–241. Castillo, V., Such, X., Caja, G., Salama, A.A.K., Albanell, E., Casals, R., 2008. Changes in alveolar and cisternal compartments induced by milking interval in the udder of dairy ewes. J. Dairy Sci. 91, 3403–3411. Hernandez, L.L., Stiening, C.M., Wheelock, J.B., Baumgard, L.H., Parkhurst, A.M., Collier, R.J., 2008. Evaluation of serotonin as a feedback inhibitor of lactation in the bovine. J. Dairy Sci. 91, 1834–1844. Jarrige, J., 1990. Alimentación de bovinos, ovinos y caprinos (Nutrition in bovine, ovine and caprine), first ed. Mundi Prensa, Madrid, Spain. Komara, M., Boutinaud, M., Ben Chedly, H., Guinard-Flament, J., Marnet, P.G., 2009. Once-daily milking effects in high-yielding alpine dairy goats. J. Dairy Sci. 92, 5447–5455. Labussière, J., 1988. Review of the physiological and anatomical factors influencingthemilkingability of ewes and theorganizationofmilking. Livest. Prod. Sci. 18, 253–274. Marnet, P.G., Komara, M., 2008. Management systems with extended milking intervals in ruminants: regulation of production and quality of milk. J. Anim. Sci. 86, 47–56. Marnet, P.G., McKusick, B.C., 2001. Regulation of milk ejection and milkability in small ruminants. Livest. Prod. Sci. 70, 125–133. Nudda, A., Bencini, R., Mijatovic, S., Pulina, G., 2002. The yield and composition of milk in Sarda, Awassi, and Merino sheep milked unilaterally at different frequencies. J. Dairy Sci. 85, 2879–2884. Papachristoforou, C., Roushias, A., Mavrogenis, A.P., 1982. The effect of milking frequency on the milk production of Chios ewes and Damascus goats. Ann. Zootech. 31, 37–46. Peaker, M., Blatchford, D.R., 1988. Distribution of milk in the goat mammary gland and its relation to the rate and control of milk secretion. J. Dairy Res. 55, 41–48. Peris, S., Such, X., Caja, G., 1996. Milkability of Murciano-Granadina dairy goats. Milk partitioning and flow rate during machine milking according to parity, prolificacy and mode of suckling. J. Dairy Res. 63, 1–9. Rovai, M., Caja, G., Such, X., 2008. Evaluation of udder cisterns and effects on milk yield of dairy ewes. J. Dairy Sci. 91, 4622–4629. Salama, A.A.K., Such, X., Caja, G., Rovai, M., Casals, R., Albanell, E., Marín, M.P., Martí, A., 2003. Effects of once versus twice daily milking throughout lactation on milk yield and milk composition in dairy goats. J. Dairy Sci. 86, 1673–1680. Salama, A.A.K., Caja, G., Such, X., Peris, S., Sorensen, A., Knight, C.H., 2004. Changes in cisternal udder compartment induced by milking interval in dairy goats milked once or twice daily. J. Dairy Sci. 87, 1181–1187. Silanikove, N., Shamay, A., Shinder, D., Moran, A., 2000. Stress down regulates milk yield in cows by plasmin induced -casein product that blocks K+ channels on the apical membranes. Life Sci. 67, 2201–2212. Silanikove, N., Shapiro, F., Shinder, D., 2009. Acute heat stress brings down milk secretion in dairy cows by up-regulating the activity of the milkborne negative feedback regulatory system. BMC Physiol. 9, 13. Silanikove, N., Leitner, G., Merin, U., Prosser, C., 2010. Recent advances in exploiting goat’s milk: quality, safety and production aspects. Small Rumin. Res. 89, 110–124. Suárez-Trujillo, A., Capote, J., Argüello, A., Castro, N., Morales-delaNuez, A., Torres, A., Morales, J., Rivero, M., 2013. Effects of breed and milking frequencyonudderhistological structures in dairygoats.J.Appl. Anim. Res. 41, 166–172. Torres, A., Castro, N., Hernández-Castellano, L.E., Argüello, A., Capote, J., 2013. Effects of milking frequency on udder morphology, milk partitioning, and milk quality in 3 dairy goat breeds. J. Dairy Sci. 96, 1071–1074. Wall, E.H., McFadden, T.B., 2008. Use it or lose it: enhancing milk production efficiency by frequent milking of dairy cows. J. Anim. Sci. 86, 27–36. Wellnitz, O., Bruckmaier, R.M., Albrecht, C., Blum, J.W., 1999. Atosiban, an oxytocin receptor blocking agent: pharmacokinetics and inhibition of milk ejection in dairy cows. J. Dairy Res. 66, 1–8. Wilde, C.J., Knight, C.H., 1990. Milk yield and mammary function in goats during and after once-daily milking. J. Dairy Res. 57, 441–447.
MANUSCRITO 3
MANUSCRITO 3 85 1 Short-term effects of milking frequency on milk yield, milk composition, SCC and 1 milk protein profile in dairy goats 2 Alexandr Torres1, Lorenzo-Enrique Hernández-Castellano2, Antonio 3 Morales-delaNuez2, Davinia Sánchez-Macías3, Isabel Moreno-Indias2, 4 Noemi Castro2, Juan Capote1 and Anastasio Argüello2* 5 1 Instituto Canario de Investigaciones Agrarias, La Laguna, Tenerife 38200, Spain. 6 2 Department of Animal Science, Universidad de Las Palmas de Gran Canaria, Arucas 7 35413, Spain. 8 3 Agroindustrial Engineering Department, Universidad Nacional de Chimborazo. 9 Riobamba 060150, Ecuador. 10 * Corresponding author: Anastasio Argüello, Fac. Veterinaria s/n, 35413 Arucas, Spain. 11 Tel.: +34 928451094; fax: +34 928451142. E-mail address: [email protected] 12 13 14 15 16 17 18 19 20 21 22 23 24
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 86 2 The goats in Canary Islands are milked once daily by tradition, but in other areas, is 25 carried out two times, with an increase of milk yield. Therefore it is important know if 26 the increase of milking frequency can improve the production without impairing the 27 milk quality. The objective of this study was to investigate the short term effects of 3 28 milking frequencies on milk yield, milk composition, SCC, and milk protein profile in 29 dairy goats traditionally milked once a day. Twelve Majorera goats in early lactation (48 30 ± 4 d in milk) were used to determine the milk yield, milk composition, somatic cell 31 count, and milk protein profile at 3 different milking frequencies. During a 5-wk period, 32 goats were milked once a day (X1) at wk 1 and 5, twice a day (X2) at wk 2 and 4, and 33 three times a day (X3) at wk 3. Milk recording and sampling were done on the last day 34 of each experimental week. Milk yield increased by 26% from X1 to X2. No differences 35 were obtained when switched from X2 to X3, and from X3 to X2. The goats recovered 36 the production level when they returned to X1. Different patterns of changes in the milk 37 constituents due to milking frequency were observed. Fat percentages increased when 38 switched from X1 to X2, there was a significant decrease from X2 to X3, and continued 39 to decline as milking frequency was decreased. Protein and lactose percentages were 40 similar among X1, X2, and X3. SCC values were similar when goats were milked X1, 41 X2, and X3, but then increased slightly when milking frequency returned to X2 and X1. 42 Finally, different patterns were observed for caseins (αS1-CN, αS2-CN, β-CN, κ-CN). 43 Thus, milking frequency did not affect the proportion of αS1-CN in milk, while αS2-CN 44 and β-CN increased from X1 to X2, stayed stable from X2 to X3, and then decreased as 45 milking frequency decreased. In contrast, κ-CN decreased from X1 to X2, and 46 recovered to initial values when milking frequency was returned to X1. 47 48 Keywords: milking frequency, milk yield, milk quality, dairy goat. 49
MANUSCRITO 3 87 3 Goat research needs progress rapidly to reach the level of knowledge of other 50 species like cattle or sheep, especially in milk production (Argüello, 2011). Many 51 studies seek to implement management systems in dairy farms with extended milking 52 intervals, or to minimize additional cost associated with extra milking if it is 53 outweighed by the value of additional milk obtained as observed in dairy cows (Wall & 54 McFadden, 2008). Milking is done twice daily (X2) in countries with high-yielding 55 dairy goats (Capote et al. 2009). However, dairy farmers want to reduce their labor 56 requirements associated with milking, to devote time to other farm practices or to social 57 activities (Komara et al. 2009). In this way, the practice of once daily milking (X1) is 58 viewed with interest by dairy farmers. In contrast, thrice daily milking (X3) is a 59 relatively novel management practice and it is not generally used in small ruminants, 60 but in dairy cows it has emerged as an effective management tool for dairy farmers to 61 increase milk production (Wall & McFadden, 2008). 62 Silanikove et al. (2010) explained that high milk producing goats, as Saanen, 63 selected to high alveolar to cistern compartment ratio, are the most sensitive to changes 64 in milking frequency. In contrast, medium milk producing goats, as Majorera, may 65 attain their genetic potential for milk yield in X1 regimen due to selection for high 66 cistern capacity (Torres et al. 2013). Previous studies revealed losses in milk yield of 67 X1 of 8 to 45% compared to X2 (Mocquot & Auran, 1974; Capote et al. 2009) and 68 increases of 8 to 28% when the goats were milked X3 instead of X2 (Henderson et al. 69 1985; Boutinaud et al. 2003). The wide variation in milk yield due to milking frequency 70 in the literature reports is a consequence of differences in breed, lactation stage, level of 71 production, duration of X1, X2 or X3, and individual characteristics (Marnet & 72 Komara, 2008). Additionally, the regulation of milk components synthesis and somatic 73
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 88 4 cells are dependent on the milking intervals, which can influence on the milk quality 74 (Marnet & Komara, 2008). 75 The hypothesis of this research paper is that 3 milking frequencies might have 76 minor effect on milk yield and chemical composition in a goat breed that is generally 77 milked X1. In addition, no information regarding the influence of milking interval on 78 milk protein profile in dairy goats is available. Therefore, the objective of this study was 79 to investigate the short term effects of 3 milking frequencies on milk yield, milk 80 composition, SCC, and milk protein profile in dairy goats traditionally milked X1. 81 82 Materials and Methods 83 The experimental animal procedures were approved by the Ethical Committee of 84 the Universidad de Las Palmas de Gran Canaria. A total of 12 Majorera goats were in 85 second parity with 48 ± 4 DIM at the beginning of the experiment. The goats which 86 were used in the experiment were from the experimental farm of the Faculty of 87 Veterinary of this University. Kids were separated from their dams within 8 h of birth. 88 The milking frequency before the start of the experimental period was once per day. 89 During a 5-wk period, goats were milked: once daily at wk 1 and 5 (X1, at 09:00), twice 90 daily at wk 2 and 4 (X2, at 09:00 and 17:00), and thrice daily at wk 3 (X3, at 09:00, 91 13:00, and 19:00). The animals had access to wheat straw ad libitum and a vitamin92 mineral corrector. The supplement per goat was 800 g/d of alfalfa and 1200 g/d of a mix 93 of maize, lucerne, and dehydrated beetroot, which it meets the nutritional requirements 94 in accordance with the guidelines issued for lactating goats by Institut National de la 95 Recherche Agronomique (INRA, Paris, France; Jarrige, 1990). The amount of 96 supplement did not differ according to milking frequency. Goats were milked in a 97 double 12-stall parallel milking parlor (Alfa Laval Iberia SA, Madrid, Spain) equipped 98
MANUSCRITO 3 95 11 X1 to X2. However, Svennersten-Sjaunja et al. (2007) reported a lower plasmin activity 248 when milking frequency was increased in dairy cows, but proteolytic degradation of 249 milk proteins was maintained. Therefore, more experiments will be necessary to 250 evaluate the plasmin activity at different milking frequencies and its effects on 251 degradation of milk proteins in dairy goats. 252 In conclusion, short-term changes of the normal milking frequency in goats 253 traditionally milked X1 during early lactation can affect milk production as reflected the 254 high increase in milk yield when milking frequency was increased from X1 to X2. 255 However, the changes in milk quality, especially in the fat content and milk protein 256 profile, requires new studies on how the milking frequency affect the yield and quality 257 of the cheeses, because the goat milk in Canary Islands is used mainly for cheese 258 production. In addition, the modification in milk yield did not take place when goats 259 were switched from X2 to X3, but the decreased in fat content requires further studies to 260 evaluate the factors that cause this decline. 261 262 This research was supported by grant AGL 2006-08444/GAN from the Spanish 263 Government. The authors want to thank A. Alavoine, G. Pons, V. Bissières, and S. 264 Cyrille from École Vetérinaire de Toulouse (France) for their technical assistance 265 during the experiment. 266 267 References 268 Argüello A 2011 Trends in goat research, a review. Journal of Applied Animal 269 Research 39 429–434 270 Bastian ED 1996 Plasmin in milk and dairy products: An update. International Dairy 271 Journal 6 435–457 272
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 96 12 de Bie L, Berger YM & Thomas DL 2000 The effect of three times a day milking at the 273 beginning of lactation on the milk production of East Friesian crossbred ewes. 274 Proceedings of the 6th Great Lakes Dairy Sheep Symposium 1–9 275 Boutinaud M, Rousseau C, Keisler DH & Jammes H 2003 Growth hormone and 276 milking frequency act differently on goat mammary gland in late lactation. 277 Journal of Dairy Science 86 509–520 278 Capote J, López JL, Caja G, Peris S, Argüello A & Darmanin N 1999 The effects of 279 milking once or twice daily throughout lactation on milk production of Canaria 280 dairy goats. In Milking and milk production of dairy sheep and goats, pp 267– 281 273 (Ed. F Barillet & NP Zervas) Wageningen: Wageningen Pers 282 Capote J, Castro N, Caja G, Fernández G, Morales-delaNuez A & Argüello A 2009 The 283 effects of the milking frequency and milk production levels on milk partitioning 284 in Tinerfeña dairy goats. Milchwissenschaft 64 239–241 285 Grieve PA & Kitchen BJ 1985 Proteolysis in milk: the significance of the proteinases 286 originating from leucocytes and a comparison of the action of leucocyte, 287 bacterial and natural milk proteinases on casein. Journal of Dairy Research 101– 288 112 289 Henderson AJ, Blatchford DR & Peaker M 1985 The effects of long-term thrice-daily 290 milking on milk secretion in the goat: evidence for mammary growth. Quarterly 291 Journal of Experimental Physiology 70 557–565 292 Hernández-Castellano LE, Torres A, Alavoine A, Ruiz-Díaz MD, Argüello A, Capote C 293 & Castro N 2011 Effect of milking frequency on milk immunoglobulin 294 concentration (IgG, IgM and IgA) and chitotriosidase activity in Majorera goats. 295 Small Ruminant Research 98 70–72 296
MANUSCRITO 3 97 13 Hopster H, Bruckmaier RM, Van der Werf JTN, Korte SM, Macuhova J, Korte-Bouws 297 G & van Reenen CG 2002 Strees responses during milking; comparing 298 conventional and automatic milking in primiparous dairy cows. Journal of Dairy 299 Science 85 3206–3216 300 Jarrige J 1990 Alimentación de bovinos, ovinos y caprinos [Nutrition in cattle, sheep 301 and goats]. Madrid: Mundi-Prensa 302 Kamote HI, Holmes CW, Mackenzie DDS, Holdaway RJ & Wickham BW 1994 Effects 303 of once-daily milking in later lactation on cows with either low or high initial 304 somatic cell counts. Proceedings of the New Zealand Society of Animal 305 Production 54 285–287 306 Klei LR, Lynch JM, Barbano D, Oltenacu P, Lednor AJ & Bandler DK 1997 Influence 307 of milking three times a day on milk quality. Journal of Dairy Science 80 427– 308 436 309 Komara M, Boutinaud M, Ben Chedly H, Guinard-Flament J & Marnet PG 2009 Once310 daily milking effects in high-yielding alpine dairy goats. Journal of Dairy 311 Science 92 5447–5455 312 Laemmli UK 1970 Cleavage of structural proteins during the assembly of the head of 313 bacteriophage T4. Nature 227 680–685 314 Lakic B, Svennersten-Sjaunja K, Norell L, Dernfalk J & Östensson K 2011 The effect 315 of a single prolonged milking interval on inflammatory parameters, milk 316 composition and yield in dairy cows. Veterinary Immunology and 317 Immunopathology 140 110–118 318 Marnet PG & Komara M 2008 Management systems with extended milking intervals in 319 ruminants: Regulation of production and quality of milk. Journal of Animal 320 Science 86 47–56 321
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 98 14 McKusick BC, Thomas DL, Berger YM & Marnet PG 2002 Effect of milking interval 322 on alveolar versus cisternal milk accumulation and milk production and 323 composition in dairy ewes. Journal of Dairy Science 85 2197–2206 324 Mocquot JC & Auran T 1974 Effets de différentes fréquences de traite sur la production 325 laitière des caprins [Effects of milking frequency on milk production of goats]. 326 Annales de Génétique et de Sélection Animale 6 463–476 327 Negrao JA, Porcionato MA, Passille A & Rushen J 2004 Cortisol in saliva and plasma 328 of cattle after ACTH administration and milking. Journal of Dairy Science 87 329 1713–1718 330 Paape MJ, Poutrel B, Contreras A, Marco JC & Capuco AV 2001 Milk somatic cells 331 and lactation in small ruminants. Journal of Dairy Science 84 E237–E244 332 Raskin RL, Raskin M & Baldwin RL 1973 Effects of chronic insulin and cortisol 333 administration on lactational performance and mammary metabolism in rats. 334 Journal of Dairy Science 56 1033–1041 335 Salama AAK, Such X, Caja G, Rovai M, Casals R, Albanell E, Marín MP & Martí A 336 2003 Effects of once versus twice daily milking throughout lactation on milk 337 yield and milk composition in dairy goats. Journal of Dairy Science 86 1673– 338 1680 339 Silanikove N, Leitner G, Merin U & Prosser C 2010. Recent advances in exploiting 340 goat's milk: Quality, safety and production aspects. Small Ruminant Research 89 341 110–124 342 Shamay A, Homans R, Fuerman Y, Levin I, Barash H, Silanikove N & Mabjeesh J 343 2005 Expression of albumin in nonhepatic tissues and its synthesys by the 344 bovine mammary gland. Journal or Dairy Science 88 569–576 345
MANUSCRITO 3 99 15 Sorensen A, Muir DD & Knight CH 2001 Thrice-daily milking throughout lactation 346 maintains epithelial integrity and thereby improves milk protein quality. Journal 347 of Dairy Research 68 15–25 348 Svennersten-Sjaunja K, Wiking L, Edvardsson A, Bavius A-K, Larsen LB & Nielsen 349 JH 2007 Effect of frequent milking on milk fat and protein. Journal of Animal 350 and Feed Sciences 16 151–155 351 Torres A, Castro N, Hernández-Castellano LE, Argüello A & Capote J 2013 Effects of 352 milking frequency on udder morphology, milk partitioning, and milk quality in 3 353 dairy goat breeds. Journal of Dairy Science 96 1071–1074 354 Wall EH & McFadden TB 2008 Use it or lose it: Enhancing milk production efficiency 355 by frequent milking of dairy cows. Journal of Animal Science 86 27–36 356 357 358 359 360 361 362 363 364 365 366 367 368 369
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 100 16 Table 1. Milk yield, milk composition, and SCC from dairy goats milked at different 370 milking frequencies†‡ 371 Milking Frequency§ X1 X2 X3 X2 X1 SEM P value Milk yield (L/d) 1.69b 2.13a 2.09a 2.01a 1.89b 0.127 0.001 Fat (%) 3.86b 4.38a 3.61b 3.34c 3.13c 0.084 0.001 Protein (%) 3.39 3.06 3.07 3.03 3.12 0.054 0.073 Lactose (%) 5.17 5.09 5.26 5.21 5.22 0.035 0.514 Total Solids (%) 13.24a 13.34a 12.74b 12.26c 12.30c 0.109 0.001 SCC (log/ml) 5.99ab 5.82b 5.88ab 6.21a 6.06a 0.077 0.050 a–cMeans with different superscripts within the same row are different (P < 0.05) 372 † Data are least squares means and standard error of means 373 ‡ Milk composition and SCC were determined with milk samples from a.m. milking for 374 X2 and X3 375 § X1 = once daily; X2 = twice daily; X3 = thrice daily 376 377 378 379 380 381 382 383 384 385 386
MANUSCRITO 3 101 17 Table 2. Protein profile from dairy goats milked at different milking frequencies†‡ 387 Milking Frequency§ Protein (%)¶ X1 X2 X3 X2 X1 SEM P value αS1-CN 11.15 10.41 11.67 10.03 10.36 0.399 0.302 αS2-CN 16.22bc 20.86a 20.63a 18.05b 15.70c 0.975 0.001 β-CN 21.63b 25.95a 25.29a 24.39ab 22.85b 0.692 0.021 κ-CN 12.01a 9.24b 9.64b 8.29b 9.84ab 0.513 0.038 β-Lg 14.67a 15.44a 14.68a 15.39a 12.96b 0.449 0.045 α-La 10.43a 10.30ab 8.73b 9.95ab 11.52a 0.509 0.050 LF 3.02b 1.57b 2.10b 3.66ab 4.97a 0.558 0.007 SA 3.91ab 2.40b 3.22b 4.89a 5.30a 0.501 0.001 IgH 3.74ab 2.38b 2.61ab 3.28ab 4.20a 0.390 0.042 IgL 3.17a 1.45b 1.43b 2.09ab 2.31ab 0.421 0.010 a–cMeans with different superscripts within the same row are different (P < 0.05) 388 †Data are least squares means and standard error of means 389 ‡Protein profile was determined with milk samples from a.m. milking for X2 and X3 390 § X1 = once daily; X2 = twice daily; X3 = thrice daily 391 ¶ CN = casein; β-Lg = β-lactoglobulin; α-La = α-lactalbumin; LF = lactoferrin; SA = 392 serum albumin; IgH = immunoglobulin G heavy-chain; IgL = immunoglobulin G light393 chain 394 395 396 397 398 399
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 102 18 Figure 1. SDS-PAGE patterns of milk proteins from dairy goats (lanes 1–9 and 11–13) 400 milked at different milking frequencies (X1 = once daily; X2 = twice daily; X3 = thrice 401 daily). 402 403
MANUSCRITO 4
MANUSCRITO 4 111 7 Oxytocin treatments did not affect the milk composition (Table 1). Lollivier and 151 Marnet (2005b) observed changes in protein content due to oxytocin injection in dairy 152 goats not milked immediately (28.9 vs. 27.6 g/kg in control and oxytocin group, 153 respectively), but fat (33.2 vs. 34.3 g/kg) and lactose contents (44.9 vs. 45.3 g/kg) were 154 unaffected. In cows, Caja et al. (2004) demonstrated a back-flux of milk to the ductal 155 and alveolar compartments when they are not milked promptly after milk letdown, 156 which influences the transference of milk components, as the upward movement of the 157 fat globules in the opposite direction to the downward draining and newly secreted milk 158 (Ayadi et al., 2004). However, Salama et al. (2004) indicated the absence of recoil and 159 milk return from cistern to alveoli in goats, due to the greater cisternal milk percentages 160 and the small contact surface between the alveolar and cisternal compartments. 161 162 Experiment 2. 163 Total milk volumes and percentages of machine milk and residual milk at 1200, 164 1600 and 2000 h are presented in Table 2. No differences were observed in total milk 165 volumes due to treatments at different milking times (P > 0.05). Since the control goats 166 were not subjected to a complete emptying of the udder, the milk accumulated in the 167 alveoli and small ducts was transferred to the cistern and was obtained in the next 168 milking; while the other goats began to store milk in the alveolar tissue which was 169 ejected after having received doses of oxytocin. Thus, there was no effect of treatments 170 on total milk volume within the udder. On the other hand, percentages of residual milk 171 obtained after saline solution injection were lower (P < 0.05) in control group (< 20%) 172 than oxytocin groups (ranged from 38.31 to 59.79%) at 1200, 1600 and 2000 h, which 173 corroborate that oxytocin has an effect on the milk transfer from alveolar tissue to 174 cistern. Moreover, the absence of differences in the milk partitioning among the 4 175
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 112 8 oxytocin groups at these intervals (P > 0.05), could indicate that the contraction of the 176 myoepithelial cells that surround the mammary alveoli is similar between low and high 177 doses of oxytocin. Previously, Lollivier et al. (2002) have indicated that a complete 178 milk removal is obtained following intravenous injection with 0.1 to 1 IU of oxytocin in 179 dairy goats. 180 Fat, protein and lactose percentages in machine and residual milk are shown in 181 Table 3. Fat percentages in machine milk significantly decreased between 1200 and 182 1600 h for the studied groups, and although another decline was observed between 1600 183 and 2000 h, the differences were not significant. A similar pattern was detected in fat 184 fractions of residual milk for the oxytocin groups between 1200 and 1600h. This decline 185 in milk fat content of both fractions could be due to cortisol released in response to the 186 stress caused by the experiment. Some research work on dairy ruminants studied the 187 association of plasma cortisol levels with different factors that cause stress in animals 188 (e.g., milking) (Hopster et al., 2002; Negrao et al., 2004). Previously, Raskin et al. 189 (1973) found that cortisol may produce a decrease in milk lipid formation from glucose 190 and acetate. In addition, no differences were observed in fat percent in milk fractions 191 among oxytocin groups at any studied milking time (P > 0.05). Gorewit and Sagi (1984) 192 observed that fat percentage in total residual milk was not affected by administration of 193 different doses of oxytocin (0.5, 1, 1.5, 2, and 3 IU) in dairy cows, but they used 194 different experimental techniques for determination of residual milk. 195 Protein and lactose percentages in machine milk and residual milk were not 196 affected due to oxytocin doses at 1200, 1600 and 2000 h (P > 0.05). In cows, some 197 authors claim that there is no modification of milk protein and lactose contents 198 regardless if oxytocin is administered over medium or long periods of time, indicating 199 that the effect of oxytocin is not manifested through an effect on cell activity (Nostrand 200
MANUSCRITO 4 113 9 et al., 1991; Ballou et al., 1993). However, Gorewit and Sagi (1984) observed that milk 201 protein percentage was lower for those cows receiving higher doses of oxytocin, 202 attributed to a dilution effect as a result of increased total milk yield. 203 Milk yield, chemical composition and SCC before (day 0) and after (day 1–3) 204 injecting different treatments are presented in Table 4. In all groups, an expected 205 decrease in milk yield at day 1 after applying the treatments was observed (P < 0.05). 206 This was because 12 hours had elapsed since the last milking. Therefore, the goats 207 stored less milk inside the udder. However, there was no effect due to treatments on 208 milk production in the following days (P > 0.05), recovering similar values to day 0. 209 Bruckmaier (2003) and Macuhova et al. (2004) found a reduction of milk ejection when 210 chronic oxytocin treatment (50 IU) was withdrawn in dairy cows. It seems that the 211 reduction of spontaneously removed milk was caused by reduced contractibility of 212 myoepithelial cells in the mammary gland at the normal physiological oxytocin 213 concentrations (Macuhova et al., 2004). 214 Fat percentages declined significantly at days 1 and 2 in all studied groups, but 215 at day 3 it reached similar values to day 0 (Table 4). In contrast, protein contents 216 increased at days 1 and 2, and subsequently decreased. Lactose percentages did not 217 show significant changes in the following days after experiment. This behavior could be 218 due to different regulatory mechanisms for secretion of milk components. No statistical 219 differences were found in SCC levels for the experimental days in the oxytocin groups 220 (Table 4). Allen (1990) observed that milk SCC increased in a dose dependent manner 221 at 12, 24, 36, 48, 60, and 72 h after the injected dose (1, 10, 100, or 1000 IU), and some 222 cows had a mastitis-like response with clots in the milk. Finally, variability of SCC 223 among the groups was high, and may be due to multiple individual factors (e.g., oestrus) 224 and not necessarily a response caused by treatments. 225
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 114 10 226 CONCLUSIONS 227 The oxytocin release by the stimulatory effect of milking procedures or the 228 administration of synthetically manufactured oxytocin had no galactopoietic effect and 229 did not produce apparent changes in the milk composition on goats not milked 230 immediately, and that are traditionally milked once a day. Likewise, it did not produce 231 apparent changes in the milk composition. In addition, the absence of differences in the 232 milk partitioning and milk composition among the administration of 4 doses of oxytocin 233 indicated that the contraction of the myoepithelial cells that surround the mammary 234 alveoli is similar between low and high doses of oxytocin in dairy goats milked once a 235 day by tradition. 236 237 ACKNOWLEDGMENTS 238 This work was supported by Fondo Europeo de Desarrollo Regional-Instituto 239 Nacional de Investigación y Tecnología Agraria y Alimentaria (FEDER-INIA) 240 RTA2009-00125. 241 242 REFERENCES 243 Akers, R. M., and A. M. Lefcourt. 1982. Milkingand sucklinginduced secretion of 244 oxytocin and prolactin in parturient dairy cows. Horm. Behav. 15:87–93. 245 Allen, J. C. 1990. Milk synthesis and secretion rates in cows with milk composition 246 changed by oxytocin. J. Dairy Res. 73:975–984. 247 Ayadi, M., G. Caja, X. Such, M. Rovai, and E. Albanell. 2004. Effect of different 248 milking intervals on the composition of cisternal and alveolar milk in dairy 249 cows. J. Dairy Res. 71:304–310. 250
MANUSCRITO 4 115 11 Ballou, L. U., J. L. Bleck, G. T. Bleck, and R. D. Bremel. 1993. The effects of daily 251 oxytocin injections before and after milking on milk production, milk plasmin, 252 and milk composition. J. Dairy Sci. 76:1544–1549. 253 Bruckmaier, R. M., and J. W. Blum. 1998. Oxytocin release and milk removal in 254 ruminants. J. Dairy Sci. 81:939–949. 255 Bruckmaier, R. M. 2001. Milk ejection during machine milking in dairy cows. Livest. 256 Prod. Sci. 81:121–124. 257 Bruckmaier, R. M. 2003. Chronic oxytocin treatment causes reduced milk ejection in 258 dairy cows. J. Dairy Res. 70:123–126. 259 Caja, G., M. Ayadi, and C. H. Knight. 2004. Changes in cisternal compartment based on 260 stage of lactation and time since milk ejection in the udder of dairy cows. J. 261 Dairy Sci. 87:2409–2415. 262 Capote, J., A. Argüello, N. Castro, J. L. López, and G. Caja. 2006. Correlations between 263 udder morphology, milk yield and milking ability with different milking 264 frequencies in dairy goats. J. Dairy Sci. 89:2076–2079. 265 Capote, J., Castro, N., Caja, G., Fernández, G., Briggs, H., Argüello, A., 2008. Effects 266 of the frequency of milking and lactation stage on milk fractions and milk 267 composition in Tinerfeña dairy goats. Small Rumin. Res. 75, 252–255. 268 Gorewit, R. C., and R. Sagi. 1984. Effects of exogenous oxytocin on production and 269 milking variables of cows. J. Dairy Sci. 67:2050–2054. 270 Gorewit, R. C., K. Svennersten, W. R. Butler, and K. Uvnas-Moberg. 1992. Endocrine 271 responses in cows milked by hand and machine. J. Dairy Sci. 75:443–448. 272 Hopster, H., R. M. Bruckmaier, J. T. N. Van der Werf, S. M. Korte, J. Macuhova, G. 273 Korte-Bouws, and C. G. van Reenen. 2002. Stress responses during milking; 274
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 116 12 comparing conventional and automatic milking in primiparous dairy cows. J. 275 Dairy Sci. 85:3206–3216. 276 Jarrige, J. 1990. Alimentación de bovinos, ovinos y caprinos. 1st ed. Mundi-Prensa, 277 Madrid, Spain. 278 Knight, C. H., and M. Peaker. 1984. Mammary development and regression during 279 lactation in goats in relation to milk secretion. Q. J. Exp. Physiol. 69:331–338. 280 Lollivier, V., J. Guinard-Flament, M. Ollivier-Bousquet, and P. G. Marnet. 2002. 281 Oxytocin and milk removal: two important sources of variation in milk 282 production and milk quality during and between milkings. Reprod. Nutr. Dev. 283 42:173–186. 284 Lollivier, V., and P. G. Marnet. 2005a. Galactopoietic effect of milking in lactating 285 Holstein cows: Role of physiological doses of oxytocin. Livest. Prod. Sci. 286 95:131–142. 287 Lollivier, V., and P. G. Marnet. 2005b. Comparative study of the galactopoietics effect 288 of oxytocin during and between milkings in cows and goats. ICAR Technical 289 Series. 10:41–47. 290 Macuhova, J., V. Tancin, and R. M. Bruckmaier. 2004. Effects of oxytocin 291 administration on oxytocin release and milk ejection. J. Dairy Sci. 87:1236– 292 1244. 293 Marnet, P. G., and B. C. McKusick. 2001. Regulation of milk ejection and milkability 294 in small ruminants. Livest. Prod. Sci. 70:125–133. 295 Negrao, J. A., P. G. Marnet, and J. Labussière. 2001. Effect of milking frequency on 296 oxytocin release and milk production in dairy ewes. Small Rumin. Res. 39:181– 297 187. 298
MANUSCRITO 4 117 13 Negrao, J. A., M. A. Porcionato, A. Passille, and J. Rushen. 2004. Cortisol in saliva and 299 plasma of cattle after ACTH administration and milking. J. Dairy Sci. 87:1713– 300 1718. 301 Nostrand S. D., D. M. Galton, H. N. Erb, and D. E. Bauman. 1991. Effects of daily 302 exogenous oxytocin on lactation milk yield and composition, J. Dairy Sci. 303 74:2119–2127. 304 Peaker, M., and D. R. Blatchford. 1988. Distribution of milk in the in the goat 305 mammary gland and its relation to the rate and control of milk secretion. J. Dairy 306 Res. 55: 41–48. 307 Raskin, R. L., M. Raskin, and R. L. Baldwin. 1973. Effects of chronic insulin and 308 cortisol administration on lactational performance and mammary metabolism in 309 rats. J. Dairy Sci. 56:1033–1041. 310 Salama, A. A. K., G. Caja, X. Such, S. Peris, A. Sorensen, and C. H. Knight. 2004. 311 Changes in cisternal udder compartment induced by milking interval in dairy 312 goats milked once or twice daily. J. Dairy Sci. 87:1181–1187. 313 Such, X., G. Caja, and L. Pérez. 1999. Comparison of milking ability between 314 Manchega and Lacaune dairy ewes. Pages 45–50 in Milking and milk 315 production of dairy sheep and goats. EAAP Publication No. 95. F. Barillet and 316 N. P. Zervas, Wageningen Pers., Wageningen, The Netherlands. 317 318 319 320 321 322 323
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 118 14 Table 1. Milk yield and milk composition of goats subjected to different oxytocin treatments.1 324 Experimental weeks Parameter Treatment2 1 2 3 4 5 6 7 8 SEM Control 2.13a 2.15a 2.05a 2.04a 2.05a 2.05a 1.98ab 1.84b 0.060 OT1 2.15a 2.10a 2.14a 2.08a 2.09a 2.05ab 2.03ab 1.92b 0.072 Milk yield (L/d) OT2 2.04a 1.98a 1.95ab 2.06a 2.06a 1.95ab 1.85b 1.83b 0.055 Control 4.62 4.63 4.56 4.67 4.72 4.78 4.72 4.86 0.040 OT1 4.34 4.55 4.48 4.34 4.37 4.40 4.40 4.55 0.048 Fat (%) OT2 4.42 4.44 4.52 4.60 4.48 4.68 4.75 4.76 0.037 Control 3.82 3.80 3.81 3.83 3.86 3.87 3.88 3.89 0.016 OT1 3.81 3.79 3.75 3.79 3.77 3.79 3.80 3.81 0.014 Protein (%) OT2 3.88 3.83 3.84 3.88 3.86 3.89 3.92 3.93 0.013 Control 5.02 5.04 5.06 4.97 5.02 4.93 4.92 4.88 0.021 OT1 5.11 5.13 5.09 5.07 5.12 5.06 4.99 4.94 0.015 Lactose (%) OT2 5.05 5.05 5.09 5.01 5.09 5.01 5.01 4.92 0.023 a–bMeans with different superscripts within the same row are different (P < 0.05). 325 1Data are estimated marginal means and standard error of means. 326 2Treatment: OT1 = endogenous oxytocin; OT2 = exogenous oxytocin. 327 328 329 330 331 332 333 334 335 336 337 338 339
MANUSCRITO 4 119 15 Table 2. Total milk volume and milk partitioning of goats injected with different doses of 340 oxytocin at 4-h milking intervals.1 341 Milking time (h) Parameter Treatment 1200 1600 2000 SEM Control 277.42 244.58 248.92 21.517 0.5 IU 264.17 278.17 329.83 13.037 1 IU 278.58 225.42 265.00 9.762 2 IU 285.00 263.83 290.42 14.550 Total milk (ml) 4 IU 290.67 277.67 297.33 14.616 Control 82.48x 81.92x 87.94x 2.443 0.5 IU 53.95y 57.25y 59.13y 3.846 1 IU 49.64y 51.61y 53.87y 3.287 2 IU 52.06y 49.55y 48.97y 3.002 Machine milk (%) 4 IU 40.21b,y 57.94a,y 61.69a,y 3.316 Control 17.52y 18.08y 12.06y 2.443 0.5 IU 46.05x 42.75x 40.87x 3.846 1 IU 50.36x 48.39x 46.13x 3.287 2 IU 47.94x 50.45x 51.03x 3.002 Residual milk (%) 4 IU 59.79a,x 42.06b,x 38.31b,x 3.316 a–bMeans with different superscripts within the same row are different (P < 0.05). 342 x–yMeans with different superscripts within the same column for each item are different (P < 343 0.05). 344 1Data are estimated marginal means and standard error of means. 345 346 347 348 349 350 351 352
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 120 16 Table 3. Milk composition of machine milk and residual milk of goats injected with different 353 doses of oxytocin at 4-h milking intervals.1 354 Milking time (h) Parameter Treatment 1200 1600 2000 SEM Control 5.12a 4.22b 3.86b 0.125 0.5 IU 5.02a 4.00b 3.64b 0.139 1 IU 5.21a 4.33b 3.78b 0.223 2 IU 6.05a 4.62b 4.13b 0.170 Fat machine milk (%) 4 IU 5.58a 4.02b 3.71b 0.170 Control 5.19a 4.67ab 4.26b 0.129 0.5 IU 4.83a 3.95b 4.00b 0.131 1 IU 5.78a 4.07b 4.38b 0.195 2 IU 5.83a 4.16b 4.46b 0.156 Fat residual milk (%) 4 IU 5.55a 4.01b 4.18b 0.162 Control 2.87 2.98 2.81 0.075 0.5 IU 2.43 2.73 2.74 0.079 1 IU 2.64 2.97 2.77 0.078 2 IU 2.73 2.91 3.07 0.075 Protein machine milk (%) 4 IU 2.75 3.24 3.23 0.100 Control 3.16 3.41 3.40 0.112 0.5 IU 2.89 3.17 2.96 0.089 1 IU 2.86 3.39 3.17 0.086 2 IU 3.04 3.45 3.19 0.097 Protein residual milk (%) 4 IU 3.45 3.71 3.56 0.063 Control 4.48 4.55 4.59 0.029 0.5 IU 4.45 4.68 4.62 0.057 1 IU 4.52 4.68 4.73 0.042 2 IU 4.44 4.54 4.44 0.041 Lactose machine milk (%) 4 IU 4.50 4.41 4.45 0.045 Control 4.87 4.94 4.95 0.026 0.5 IU 4.79 4.89 4.91 0.036 1 IU 4.88 4.93 4.94 0.036 2 IU 4.83 4.89 4.94 0.032 Lactose residual milk (%) 4 IU 4.66 4.78 4.77 0.030 a–cMeans with different superscripts within the same row are different (P < 0.05). 355 1Data are estimated marginal means and standard error of means. 356
MANUSCRITO 5 127 (Stelwagen et al., 1999b). Tight junctions switch to a leaky state after approximately 18 h of milk accumulation in cows (Stelwagen et al., 1997), after 20 h in sheep (Castillo et al., 2008), and after 21 h in goats (Stelwagen et al., 1994). Moreover, Stelwagen et al. (1994) have previously shown that a decrease in the rate of milk secretion is correlated with the leakiness of mammary tight junctions observed during extended milking. However, Ben Chedly et al. (2013) found that the decrease in milk yield that occurs during once daily milking in goats is due to regulation of synthetic activity rather than to apoptosis of mammary epithelial cells or the state of the mammary gland tight junctions. The Na and K balance between the alveolar lumen and the interstitial fluid is conditioned by tight junction integrity. Thus, Na and K can freely cross the apical membrane, and the changes in the concentrations of these ions lead to corresponding intracellular changes (Stelwagen et al., 1999a). Furthermore, lactose is a component synthesized only in the mammary gland and is not secreted basolaterally in significant quantities, so its presence in blood can only be explained by its movement from milk into blood via leaky tight junctions (Stelwagen et al., 1994; Castillo et al., 2008). Knowledge about how different milking intervals affect the permeability of tight junctions in dairy goats traditionally milked once a day is required. For this reason, the objective of this study was to evaluate some indicators of leakiness of tight junction at different milking intervals in two dairy goat breeds traditionally milked once a day. 2. Material and methods The experimental animal procedures were approved by the Ethical Committee of the Universidad de Las Palmas de Gran Canaria (Arucas, Spain). The present study was performed in the experimental farm of the Instituto Canario de Investigaciones Agrarias
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 128 (Tenerife, Spain) on 32 dairy goats belonging to two breeds: Majorera (n = 8, primiparous, 2.09 ± 0.53 L/d; n = 8; multiparous, 2.11 ± 0.57 L/d), and Palmera (n = 8, primiparous, 1.35 ± 0.39 L/d; n = 8; multiparous, 1.41 ± 0.20 L/d), in mid lactation at the beginning of the experiment. The animals were fed according to the guidelines of the Institute National de la Recherche Agronomique (INRA, Paris, France) and recommendations (Jarrige, 1990). The goats were divided in 2 flocks (n = 16) balanced for parity (primiparous and multiparous) and breed (Majorera and Palmera) with similar milk yields. The experiment considered 4 milking intervals (Flock 1: 10, 14, 24, and 28 h; Flock 2: 10, 14, 24, and 32 h), where milk and blood samples were taken for analysis. Goats were milked in a double 12-stall parallel milking parlor (Alfa-Laval, Madrid, Spain) equipped with recording jars (4 L ± 5%) and a low-line milk pipeline. Milking was performed at a vacuum pressure of 42 kPa, a pulsation rate of 90 pulses/min, and a pulsation ratio of 60/40 in accordance with Capote et al. (2006). The milking routine included wiping dirt off teat ends and stripping 2-3 squirts of milk from each teat, machine milking and stripping milking, done by the operator to remove the milk remaining in the udder before cluster removal, and teat dipping in an iodine solution (P3-cide plus, Henkel Hygiene, Barcelona, Spain). Milk volumes were recorded by using the recording jars in the milking parlor. Milk samples were analyzed for determination of chemical composition, and Na and K concentrations. Blood samples were immediately taken after each milking and analyzed for determination of lactose, and Na and K concentrations. Milk fat, protein and lactose percentages were determined by using a DMA2001 Milk Analyzer (Miris Inc., Uppsala, Sweden). Concentrations of Na and K in milk were determined using atomic absorption spectrometry (AAnalyst 200 spectrometer, Perkin-Elmer, Norwalk, USA) in the
MANUSCRITO 5 129 Laboratory of Chemical Analysis of the Instituto Canario de Investigaciones Agrarias, and the concentrations of these ions in blood were measured by means of ion selective electrodes (Olympus AU2700 analyzer, Beckman Coulter, Tokyo, Japan) in the Laboratory LGS Análisis. The enzymatic assay for determination of plasma lactose (Boehringer Mannheim / R-Biopharm) was based on two reactions, one measuring galactose and the other measuring lactose and galactose; the difference between the two provided a measurement of lactose concentration. This analysis was conducted in the Laboratory of Research Unit at University Hospital (Tenerife, Spain). The statistical analyses were performed by using SPSS 15.0 software (SPSS Inc., Chicago, USA). Repeated measures analysis of variance (ANOVA), with adjustments for non-sphericity (Greenhouse-Geisser correction), was applied to evaluate milking intervals effects on studied parameters; followed by LSD post-hoc tests. Differences among experimental groups (Majorera-primiparous, Majorera-multiparous, Palmera-primiparous, Palmera-multiparous) were evaluated using a multiple comparison test following the Tukey method. Statistical differences were considered significant at P < 0.05. Data are presented as least squares means. 3. Results Milk volume (Table 1) was affected due to milking interval in both experimental flocks (P < 0.05). However, Majorera and Palmera goats did not show differences from 10to 14-h of milk accumulation, but a significant increase was observed from 14to 24-h intervals in the studied groups. In the Flock 1, milk volume at 28-h was higher than milk volume at 24-h in the studied breeds, but these differences were not significant (P > 0.05). In contrast, the goats of Flock 2 showed a dramatic increase in milk volume in Majorera primiparous (17%), Majorera multiparous (27%), Palmera
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 130 primiparous (20%), and Palmera multiparous (10%) from 24to 32-h of milk accumulation. Regarding breed effect, no significant differences were found between Majorera and Palmera goats at 10-h milking interval. Nevertheless, Majorera goats had higher milk volumes than Palmera goats at subsequent milking intervals (P < 0.05). Additionally, milk volumes were similar (P > 0.05) between primiparous and multiparous goat at different milking intervals. Milk fat percentages (Table 1) were comparable between consecutive milking intervals (P > 0.05), except for goats of the Flock 1, where milk at 14-h contained lower percentages of fat than milk at 24-h (P < 0.05). Nevertheless, there was a trend to obtain milk richer in fat content when the milking intervals differ by more than 14 hours (P < 0.05). In addition, fat percentage was not affected by breed and parity factors, both in goats of Flock 1 and 2 (P > 0.05). No significant differences were detected in milk protein percentages from 10to 14-h milking intervals in the studied groups (Table 1). Subsequently, Majorera breed had an increase in protein content when interval switched from 14to 24-h (P < 0.05), and stayed stable from 24to 28and 32-h (P > 0.05). Likewise, Palmera goats did not have differences in protein content from 24to 28and 32-h. Breed and parity had not effects on milk protein percentage at the studied milking intervals. No differences were found in milk lactose percentages in the studied goats (Table 1) when the milking interval and breed factors were considered (P > 0.05). Regarding parity effect, Palmera primiparous had higher values than Palmera multiparous at 28and 32-h (P < 0.05). However, these differences were not significant between Majorera primiparous and multiparous. Milking interval did not modify Na content in milk for Majorera goats (Table 2). Only a slight increase in Na concentration was observed for Palmera primiparous and
MANUSCRITO 5 131 multiparous (Flock 2) from 10with respect to 24and 32-h. In general, primiparous goats had lower levels of Na than multiparous goats, whereas Palmera had higher values than Majorera of these ions in milk, when the parity and breed effects were considered, respectively. Moreover, no changes were found in concentration of K in milk for the goat groups due to milking interval, breed or parity factors (P > 0.05). Goat breed and parity did not affect (P > 0.05) Na and K concentration in plasma blood at all intervals (Table 2). Besides, as milking interval increased, concentration of Na in blood plasma decreased for Majorera and Palmera in both parities (P < 0.05). Otherwise, concentration of K in blood plasma was steady until 28-h (Flock 1) and increased markedly at 32-h (Flock 2) for all goat groups. Milking interval affected (P < 0.05) lactose concentration in plasma (Table 2). It was observed that after 14-h interval, Majorera and Palmera goats in both parities dramatically increased its levels of lactose in plasma blood. Likewise, parity factor had an effect on plasma lactose, where primiparous goats exhibited lower values than multiparous goats at the studied milking intervals. Finally, no differences were observed between Majorera and Palmera breeds at the different intervals (P > 0.05). 4. Discussion The increases in milk volume with increasing milking intervals, is a consequence of a wider cisternal capacity of the studied breeds, which allowed a continuous drop of milk from alveoli to the cistern, reducing the feedback inhibitor process, the alveolar milk stasis and alveolar pressure (McKusick et al., 2002; Torres et al., 2013a). Typically in goats, 24-h of milk stasis is necessary to activate regulatory mechanisms leading to disruption of tight junctions and reduced milk secretion, longer than the 18 h required to induce a similar phenomena in cows and sheep (Marnet and
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 132 Komara, 2008). Goats have a higher proportion of milk in their cistern than ewes or cows, which most likely contributes to their ability to better maintain milk yield under extended milking (Silanikove et al., 2010). Disruption of mammary tight junctions is associated with a decrease in milk yield due to longer milking intervals (Stelwagen et al., 1994; Delamaire and GuinardFlament, 2006), which is related with cell death and a decrease in mammary activity (Ben Chedly et al., 2010). It is predicted that for milking intervals of less than 20-h in goats and 18-h in cows, the concentration of β-casein f(1–28), peptide that serves as a local regulator on milk secretion, would be higher in the cistern than in the alveoli (Silanikove et al., 2000). Therefore, the alveoli will not be exposed to the full impact of the negative feedback signal of this peptide. Extending milk stasis beyond these times exceeds the storage capacity of the cistern, resulting in the equilibration of β-casein f(1– 28) concentration between the cistern and the alveoli, and inducing disruption of the tight junction (Silanikove et al., 2010). The higher volume of milk found for Majorera goats compared with Palmera goats is due to cisternal size of each breed. Previously, Torres et al. (2013a) reported that Majorera have higher udder depth values (difference in distance between the udder floor and the cistern floor) than Palmera, which is correlated with the udder volume (Capote et al., 2006). Bruckmaier et al. (1997) explained that a large absolute cisternal volume implies that a large fraction of the milk is stored within the cisternal cavities. Castillo et al. (2008) showed a greater milk accumulation rate in Lacaune than in Manchega ewes, where Lacaune breed have a greater cisternal area than Manchega breed (Rovai et al., 2008). Milk volume in multiparous goats was higher than primiparous goats, but the statistical differences were no significant, which was unexpected. Goetsch et al. (2011)
MANUSCRITO 5 133 reported that milk production is lower for primiparous than for multiparous dairy goats. Salama et al. (2004) found that the differences in storage capacity of the cisterns between primiparous and multiparous goats were more evident after 24 h of milk accumulation, in which multiparous goats had larger cisternal area and were able to store more volume of milk in the cistern than primiparous goats. McKusick (2000) found that ewes with high milk volume-intramammary pressure ratio had a significant degree of compliance in their udders because they were able to accommodate an increase in intramammary pressure of 30% when the milking interval was extended to 24 h. Therefore, intramammary compliance or elasticity plays a significant role to accommodate the milk volumes secreted. The results obtained could be explained by the fact that primiparous goats had an optimal intramammary compliance due to adaptation of the breed to once daily milking. However, further studies are needed to verify this hypothesis. Milk fat percentages had a trend to be higher as milking interval increased. However, McKusick et al. (2002) and Castillo et al. (2008) in ewes, and Ayadi et al. (2004) in cows observed that milk fat content decreased with longer milking intervals. These authors indicate that there was transfer of milk fat from the alveoli to the cistern during early udder filling, but this transfer was no longer taking place during the later intervals. It has been reported an upward movement of the fat globules, in the opposite direction to the downward draining and newly secreted milk at extended milking in dairy cows (Ayadi et al., 2004). Conversely, this cistern recoil phenomenon did not occur in goats, where once milk is ejected, it is unable to return to the alveoli (Salama et al., 2004). In addition, Komara et al. (2009) in Alpine goats and Torres et al. (2013b) in Majorera and Palmera goats did not find differences in fat percentages between once and twice daily milking. Moreover, according to Stelwagen et al. (1997), the diameter
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 134 of milk fat globules is greater than the intercellular joints, and Komara et al. (2009) found that fat globule size between once and twice daily milking were similar for dairy goats. Therefore, changes in fat content according to milking interval are related to the regulatory mechanisms for secretion of large and high-viscosity milk fat globules relative to the components in the aqueous phase of milk (Davis et al., 1999). Milk protein percentages did not have changes at extended milking in the studied breeds, which agrees with observations in dairy cows by Ayadi et al. (2004) and dairy ewes by Castillo et al. (2008), where protein content in milk was constant after 12 h. However, McKusick et al. (2002) found an increase in milk protein fraction from 20 h in dairy ewes. The tendency of protein content to increase for extended milking intervals in some species or breeds may be explained by increased tight junction leakiness allowing serum protein entering into the milk, since casein does not move through leaky mammary tight junction (Ayadi et al., 2004; Castillo et al., 2008). However, typical milk albumin concentration (the greatest potential contributor of serum protein to milk) is too small to make an effect on protein concentration in milk, being produced and secreted by mammary epithelial cells into milk (Silanikove et al., 2013). Therefore, the changes in milk protein content according to milking interval, like milk fat content, seems are more correlated to regulation of synthetic activity of secretory cells or hydrolysis of protein rather to disruption of the mammary gland tight junctions (Ben Chedly et al., 2013). The absence of differences in milk lactose percentages found in the studied goats according to milking interval factor is related with the udder size. Thus, Castillo et al. (2008) reported a decrease in lactose content from the 20to 24-h milking interval in Manchega ewes (small udder cisterns), but not in Lacaune ewes (large udder cisterns). Decreases of milk lactose percentage seem to be due to lactose passing from milk into
MANUSCRITO 5 135 blood through impaired tight junctions associated with extended milking intervals (Stelwagen et al., 1994). However, Ben Chedly et al. (2013) proposed that the reduction of milk lactose yield is essentially due to a reduction of its synthesis by the mammary gland. In general, Na and K contents in milk were not affected by the studied milking intervals. Only a slight increase was observed in Na content for Palmera goats from 10to 24and 32 intervals. When the permeability of tight junctions increases, the concentration of Na in milk increases, and the concentration of K decreases (Stelwagen et al., 1999a). Furthermore, a reduction of Na content and an increase of K content in blood plasma would be expected during the disruption of tight junctions. In the present experiment was detected the diminution of Na values in blood plasma in the studied groups when the milking interval was increased, and the concentration of K only was increased both Majorera and Palmera goats at 32-h interval. Castillo et al. (2008) did not find differences in Na and K concentration in milk in Lacaune ewes at extended milking intervals, but Manchega ewes had an increase of Na and a decreased of K in milk after 20 h. These authors suggested that variations in ion concentration have a relationship with the adaptation to extended milking intervals of these breeds being lower in Manchega than Lacaune ewes. Furthermore, Stelwagen et al. (1994) found that Na concentration in milk increased from 16.3 mM at 0 h to 21.3 mM at 36 h, and the K concentration in milk decreased from 46.7 mM at 0 h to 34.3 mM at 36 h in Saanen goats, as consequence of tight junction disruption. In the present study, Majorera and Palmera breeds are fully adapted to once daily milking, which can explain that concentrations of Na and K were not the best indicators of leakiness of tight junctions. Despite the high variability of plasma lactose concentration obtained in the experimental groups, this increased sharply at 24-h, indicative of an increase in tight
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 136 junction permeability. Castillo et al. (2008) considered that lactose in plasma is the main indicator of mammary tight junction permeability, because changes in Na and K concentrations may reflect an alteration in the transport of these ions across transcellular rather than paracellular pathways. In Saanen goats, Stelwagen et al. (1994) showed an increase of plasma lactose concentration after 21 h of milk accumulation, whereas that in dairy cows, Stelwagen et al. (1997) observed the increase of lactose in plasma after 18 h of milk stasis. In addition, some studies which switched from twice to once daily milking in goats and cows (Stelwagen et al., 1997; Ben Chedly et al., 2013) demonstrated that the increase in blood lactose concentration is transient, suggesting that the gland gradually adapted to once daily milking. Finally, the increases of plasma lactose seem to have not been conditioned by breed effect. Nevertheless, primiparous goats had an increase more pronounced in plasma lactose values than multiparous goats at extended milking intervals, although these animals presented the highest concentrations, which may indicate that the older animals had a greater degradation in the integrity of tight junction due to different lactations. On the other hand, Castillo et al. (2008) found that Manchega ewes increased by 5-fold its plasma lactose values from 20to 24-h, whereas Lacaune ewes increased by only 1.5-fold, indicating that the tight junction leakiness effect was greater in Manchega that in Lacaune ewes. Therefore, the udder development plays an important role on degree of tight junction leakiness. 5. Conclusions The wide cisternal capacity of the Majorera and Palmera breeds allowed an increase in milk yield above to 24 h of milk accumulation. Furthermore, milk composition was not impaired when milking intervals were increased until 28 or 32 h. In regard to indicators of leakiness of tight junction, the concentrations of Na and K in
MANUSCRITO 5 143 Table 2. Effects of milking interval on concentration of Na and K in milk and plasma blood and concentration of plasma lactose in two dairy goat breeds 1 Flock 1 Flock 2 Milking interval (h) Milking interval (h) 10 14 24 28 SEM 10 14 24 32 SEM Milk Na (mM) Majorera primiparous 12.38x 13.47x 14.80x 14.99x 0.437 12.65x 14.13x 13.99x 13.33x 0.605 Majorera multiparous 18.62y 17.43y 18.17xy 19.87y 0.519 20.03y 18.74y 21.99y 20.76y 0.996 Palmera primiparous 12.53x 14.36xy 15.99x 15.41x 0.538 13.78a,x 15.56ab,xy 16.51b,x 17.02b,xy 0.880 Palmera multiparous 19.76y 22.36y 22.17y 24.36z 0.763 17.70a,y 18.29ab,y 20.87b,xy 21.28b,y 0.620 K (mM) Majorera primiparous 34.75 37.44 37.02 37.15 0.904 35.70 39.82 38.07 38.53 0.960 Majorera multiparous 36.01 38.80 42.80 39.96 1.149 38.13 41.99 40.98 40.24 0.728 Palmera primiparous 34.16 36.99 34.51 35.57 0.805 33.35 36.33 35.13 33.20 0.536 Palmera multiparous 33.36 35.76 37.44 34.02 1.131 34.65 36.32 37.93 36.44 0.839 Plasma blood Na (mM) Majorera primiparous 146.08b 145.55b 144.68a 144.23a 0.278 145.95b 145.30b 144.05a 143.90a 0.287 Majorera multiparous 148.53c 146.95bc 146.80ab 144.90a 0.517 146.88b 146.05ab 144.15a 144.45a 0.417 Palmera primiparous 146.45b 144.85ab 142.70a 142.75a 0.552 147.28b 145.93ab 143.85a 143.80a 0.455 Palmera multiparous 147.05b 145.20ab 144.18a 143.33a 0.464 147.00c 145.50bc 143.80a 144.40ab 0.365 K (mM) Majorera primiparous 5.18 5.08 5.00 5.73 0.120 5.10a 4.78a 4.73a 5.88b 0.148 Majorera multiparous 5.23 5.03 4.90 5.45 0.102 5.28ab 4.93a 4.60a 5.90b 0.165 Palmera primiparous 5.33 5.05 4.95 5.53 0.134 5.03ab 4.90a 4.55a 5.45b 0.117 Palmera multiparous 4.93 5.10 4.88 5.63 0.136 4.68a 4.58a 4.43a 5.58b 0.134 Plasma lactose (μM) Majorera primiparous 54.96a,x 66.51a,x 127.85b,x 181.05c,y 14.435 65.48a,x 84.39b,xy 140.98c,x 230.23d,y 17.707 Majorera multiparous 135.45a,y 177.23a,y 235.51b,y 328.22c,z 20.651 120.64a,y 180.95a,z 222.92b,y 308.96c,z 21.158 Palmera primiparous 44.26a,x 56.26a,x 88.73b,x 110.38c,x 10.100 43.28a,x 55.18a,x 89.71b,x 152.78c,x 12.528 Palmera multiparous 136.75a,y 160.35a,y 264.00b,y 342.21c,z 22.518 106.96a,y 128.15a,y 245.37b,y 314.44c,z 22.815 a–dMeans with different superscripts within the same row are different (P < 0.05). x–zMeans with different superscripts within the same column for each item are different (P < 0.05). 1Data are least square means and standard error of means.
CONCLUSIONES
CONCLUSIONES 147 Artículo 1 Elhechodequealrededordel80%delalechetotalqueseencuentraenlaubre,sealmacene enloscompartimentoscisternales,tantoalas14-comoalas24-h,sugierequelamayorpartedela transferencia de leche desde los alvéolos a la cisterna ocurre durante las primeras fases de llenado delaglándula.Poresarazónnoseencontrarondiferencias,enrelaciónalacomposiciónquímicade la leche cisternal, entre ambos intervalos de ordeño. Sin embargo, los diversos cambios que presentaron los contenidos de grasa, lactosa y sólidos totales en la leche alveolar, sugieren la necesidad de posteriores estudios sobre los mecanismos responsables de la eyección de la leche entre ordeños. Artículo 2 Los resultados demostraron que la práctica del doble ordeño no mejora la producción de lecherespectoaunordeñodiarioenlascabrasderazaMajorerayTinerfeña,locualesdeinterés para los sistemas de producción caprina, en donde se busca reducir los costes relacionados con la producción de leche. No obstante, el aumento significativo en la producción lechera que mostraron lascabrasderazaPalmeraalordeñardosvecesaldía,sugierequepodríaserunaprácticarentable en ciertos momentos de la lactación. Sin embargo, el contenido de proteína en leche no incrementó enconcordanciaconlaproducción.Porestarazón,senecesitanotrosestudiosparaevaluarlos efectos de la frecuencia sobre el rendimiento quesero, lo cual es un aspecto de suma importancia en la economía ganadera de Canarias. Además, el conocimiento de las estructuras de fraccionamiento de leche puede servir de base para futuros programas de selección, al objeto de mejorar la facilidad de ordeño en las razas locales. Manuscrito 3 Los cambios a corto plazo de la frecuencia normal de ordeño en cabras tradicionalmente ordeñadas una vez al día durante la lactancia temprana puede afectar la producción de leche en cabras derazaMajorera,comolodemuestraelincrementosignificativocuandosecambiadeunoadosordeños diarios. Sin embargo, las variaciones en el contenido de grasa y perfil proteico requieren estudios acerca de cómo éstas afectan la producción y calidad de los quesos, ya que la finalidad principal delasexplotacionescaprinascanariaseslafabricacióndeeseproducto.Porotrolado,lafaltade incremento en la producción durante el triple ordeño, con la disminución en los porcentajes de grasa en la leche, hace necesario futuros estudios para evaluar las causas que provocan este descenso.
Efecto de la frecuencia de ordeño sobre la producción, fraccionamiento lechero y parámetros de calidad de la leche en las cabras canarias 148 Manuscrito 4 La liberación de oxitocina por estimulación previa al ordeño y la administración de oxitocina sintética no tuvo efecto galactopoyético ni cambios aparentes en la composición química de la leche en cabras no ordeñadas inmediatamente que tradicionalmente se ordeñaban una vez al día. Además, la ausencia de diferencias en el fraccionamiento lechero y composición de la leche entre la administración de cuatro dosis de oxitocina indica que la contracción de las células mioepiteliales que rodean los alvéolos es similar en respuesta a bajas y altas dosis de esta hormona. Manuscrito 5 LaampliacapacidadcisternaldelascabrasderazaMajorerayPalmerapermitióunaumento delaproduccióndelechedespuésde24hdeacumulación.Además,lacomposiciónquímicadela lechenosevioafectadacuandolosintervalosdeordeñoseincrementaronhasta28o32h.Enloque se refiere a los indicadores de permeabilidad de las uniones celulares del epitelio mamario, las concentraciones de Na y K en leche y sangre no reflejaron un mayor grado de permeabilidad, al menos encabrastradicionalmenteordeñadasunavezaldía.Porotraparte,elaumentoenlaconcentración delactosaenelplasmasanguíneo,despuésde14hdeacumulacióndeleche,nopermitióprecisar silaroturadelasunionescelularesseprodujoantesodespuésde24h,osedebíaalflujonormalde lactosa desde el lado apical al basolateral por el estado de dichas uniones en cabras acostumbradas a largo intervalos de ordeño. Adicionalmente, los resultados no mostraron una relación entre los rendimientos de leche y daños en la permeabilidad de las uniones celulares, lo cual es interesante para el desarrollo de programas de selección, en las zonas que requieran intervalos de ordeño más largos.