Supplementing the diet of dairy goats with dried orange pulp throughout lactation: I. effect on milk performance, nutrient utilisation, blood parameters and production economics

animals Article Supplementing the Diet of Dairy Goats with Dried Orange Pulp throughout Lactation: I. Effect on Milk Performance, Nutrient Utilisation, Blood Parameters and Production Economics JoséLuis Guzmán1, Ignacio Martín-García2, Alejandro Pérez-Écija 3, Manuel David García-Brenes 4, Luis Ángel Zarazaga 1and Manuel Delgado-Pertíñez 5,*   Citation: Guzmán, J.L.; Martín-García, I.; Pérez-Écija, A.; García-Brenes, M.D.; Zarazaga, L.Á.; Delgado-Pertíñez, M. Supplementing the Diet of Dairy Goats with Dried Orange Pulp throughout Lactation: I. Effect on Milk Performance, Nutrient Utilisation, Blood Parameters and Production Economics. Animals 2021, 11, 2601. https://doi.org/10.3390/ ani11092601 Academic Editor: Igino Andrighetto Received: 6 July 2021 Accepted: 2 September 2021 Published: 4 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1Departamento de Ciencias Agroforestales, Escuela Técnica Superior de Ingeniería, Universidad de Huelva, “Campus de Excelencia Internacional Agroalimentario, ceiA3”, Campus Universitario de la Rábida, Carretera Huelva-Palos de la Frontera, s/n., 21819 Palos de la Frontera (Huelva), Spain; [email protected] (J.L.G.); [email protected] (L.Á.Z.) 2Estación Experimental del Zaidín (CSIC), Profesor Albareda 1, 18008 Granada, Spain; [email protected] 3Departamento de Medicina y Cirugía Animal, Campus Rabanales, Universidad de Córdoba, 14104 Córdoba, Spain; alejandr[email protected] 4 Departamento de Economía Aplicada II. Escuela Técnica Superior de Ingeniería Agronómica, Universidad de Sevilla, Carretera de Utrera Km 1, 41013 Sevilla, Spain; [email protected] 5Departamento de Agronomía, Escuela Técnica Superior de Ingeniería Agronómica, Universidad de Sevilla, Ctra. Utrera Km 1, 41013 Sevilla, Spain *Correspondence: [email protected]; Tel.: +34-954486449 Simple Summary: Dried orange pulp can conveniently replace cereals in ruminant diets; however, no published reports have considered a similar substitution for the goat diet throughout lactation. Therefore, in this study, we evaluated the effects of cereal replacement (40% and 80%) by dried orange pulp in the diet of Payoya breed goats during the entire lactation period (180 days) on milk yield and composition, blood metabolites and production economics. Also evaluated, in mid-lactation, were the nutrient utilisation and ruminal fermentation of the dried orange pulp diets. Milk production and gross composition did not change in goats fed diets that included dried orange pulp. A decrease in nitrogen availability and retention was observed, while an increase detected in the digestibility of cellulose likely boosted rumen microbial protein synthesis. No pathological effects of dried orange pulp supplementation were detected in blood metabolites. The partial substitution of cereals for dried orange pulp reduced costs and raised economic profits. In conclusion, the partial replacement of cereals by dried orange pulp is a profitable and healthy nutritional strategy in dairy goats that does not compromise their productivity and is suitable for the entire lactation period. Abstract: Dried orange pulp (DOP) can be incorporated into ruminant diets, but no reports have considered this strategy during the entire lactation period in goats. Two experiments were performed using lactating Payoya goats. In experiment 1, to study the effect, over 180 days, of DOP on milk yield and composition, blood metabolites and economic values, 44 primiparous goats were allocated into three groups: control diet (concentrate plus lucerne) and DOP40 and DOP80 diets, in which DOP replaced 40% and 80%, respectively, of the cereals. Nutrient digestibility and rumen fermentation were also studied (experiment 2). The DOP diets did not affect milk yield and composition. DOP triggered lower intake and digestibility of ether extract and crude protein. Ruminal fermentation was unaffected by DOP, except for a decrease in butyrate for DOP80. The energy balance was unaltered by diet while the balance and retention of nitrogen decreased. Regarding plasma biochemistry, DOP supplementation caused changes that could indicate an improvement in hepatic function and reduced muscular damage and oxidative muscular stress. Moreover, DOP80 provided a profit increase of EUR 3.27/goat. In conclusion, the partial replacement of cereals by DOP is a profitable and healthy nutritional strategy in dairy goats and is suitable for the entire lactation period without compromising productivity. Animals 2021,11, 2601. https://doi.org/10.3390/ani11092601 https://www.mdpi.com/journal/animals Animals 2021,11, 2601 2 of 15 Keywords: Payoya breed; citrus byproduct; digestibility; rumen fermentation; complete lactation; blood chemistry; economic profit 1. Introduction Enormous possibilities exist for using agroindustrial byproducts in animal feed if productivity or product quality is not compromised. The use of byproducts could eliminate environmental pollution problems and expenses derived from their management and disposal, while reducing livestock dependence on raw materials that can be consumed directly by humans, contributing to the sustainable use of biological resources. For example, Romero-Huelva et al. [ 1 ] concluded that the mixture of tomato fruits, citrus pulp, brewer’s grain and brewer’s yeast could replace 47% of conventional ingredients (corn, wheat bran, sunflower meal and soy flour) in the concentrate of the dairy goat diet, reducing feeding costs and methane production and leading to a healthier fatty acid profile in milk without compromising nutrient utilisation or milk yield. Orange pulp is a byproduct of the orange juice industry that can be used fresh, pressed, dried and in pellets. Spain is the largest producer of oranges in the EU and the sixth largest producer worldwide [ 2 ]. In 2018, the country produced 3.9 million tons [ 3 ], 94.7% of which was produced in Valencia and Andalusia. As the production rate is 0.63 tons of pulp per ton of oranges [ 4 ], Spain produced 2.4 million tons of orange pulp in 2018. Moreover, Spain is also a major producer of goat livestock, and in 2018, it produced the second-highest number of goats of any European country (2.76 ×106) [2]. The main use of orange pulp is in rations for high-production ruminants since its nutritional value is similar to that of cereal grains. Including the pulp in ruminant feed as a total or partial substitute for cereals could also decrease the cost of food. There are very few published works on the effects of feeding orange pulp on the milk yield of dairy goats. López et al. [ 5 ] and Ibáñez et al. [ 6 ] have verified, in short experimental periods during mid-lactation, that replacing corn or barley grain with citrus pulp in the diet of Murciano-Granadina goats did not affect food intake, digestibility of most nutrients, milk production or gross composition. Very recently, our group examined how replacing cereal concentrates with dehydrated orange pulp (DOP) in the diet of goats affected the milk performance and health status, but only during early lactation [ 7 ]. Our group demonstrated that DOP supplementation did not cause any pathological blood chemistry alteration in goats. Moreover, supplemented diets correlated with lower blood markers of muscular stress and damage during late gestation. As a result of this preliminary work, our starting hypothesis is that DOP can partially replace cereals in the diet of the dairy goat over long term (early, mid and late lactation) dietary supplementation and would not detrimentally affect goat milk performance, health status or nutrient utilisation, and could be a practical and cost-effective alternative to cereals. Therefore, this work studies the effects of substituting cereal by DOP in the diet of dairy goats during the entire lactation period on dam milk yield and composition, blood metabolites and economic values. In addition, a second experiment was conducted in midlactation to evaluate the nutrient utilisation and ruminal fermentation of goats consuming the experimental diets. 2. Materials and Methods Two in vivo experiments were performed using lactating Payoya goats at the experimental farm of the University of Huelva (Huelva, Spain). Experiment 1 studied the effect of replacing cereal with DOP in the diet of dairy goats during the entire lactation period (180 days) on dam milk yield and composition, blood metabolites and economic values. In addition, a short-term in vivo trial (experiment 2) was conducted mid-lactation using the same experimental diets to evaluate nutrient utilisation and ruminal fermentation. Animals 2021,11, 2601 3 of 15 2.1. Experimental Diets, Goats and Experimental Procedure (Experiment 1) Forty-four primiparous goats were assigned to three experimental groups, each with a different diet; the groups were balanced according to the goats’ live weight (LW) and body condition scores (BCS) [8]. These goats had been included in a previous experiment that assessed the effect of DOP in the diet of dairy goats on milk yield and composition and blood parameters of dams and growth performance and carcass quality of kids [ 7 ]. The animals were housed in a communal pen, and each experimental group was separated by metal barriers with free access to a yard. The three experimental diets were as follows: control (CD, n= 14), fed a commercial concentrate plus alfalfa hay as forage; DOP40 (n= 16) based on CD, but with 40% of the cereals in the concentrate replaced by DOP; DOP80 (n= 14) , based on CD, with 80% of the cereals in the concentrate replaced by DOP. After parturition, the animals were offered the experimental diets adapted to early-mid- and late lactation. The formulation of the rations and the chemical composition of the isoenergetic and isoproteic diets are shown in Table 1. Formulations were designed using the Feed Ration Balancer (Format Solutions) software, version 2.0 (2017; Cargill, Inc., Wayzata, MN, USA). Hay and concentrate samples were prepared for analysis in each lactation stage (early-mid- and late) by mixing equal amounts of the subsamples collected through the lactation period and storing them at 4 ◦C. Table 1. Ration ingredients and proximate composition of the experimental diets 1during the entire lactation period. Items Early and Mid-Lactation Late Lactation Control DOP40 DOP80 Control DOP40 DOP80 Ration ingredients, % dry matter (DM) basis Alfalfa hay 17.44 17.53 17.64 20.16 20.28 20.44 Concentrate Dehydrated orange pulp (pellets) 0 19.96 39.87 0.00 19.36 38.64 Grain oats 22.10 13.23 4.38 21.44 12.,83 4.24 Grain barley 8.53 5.11 1.70 8.28 4.96 1.65 Grain corn 19.34 11.61 3.89 18.76 11.25 3.77 Soy flour, 44% 7.31 10.23 12.97 7.09 9.92 12.57 Sunflower pellets, 28% 12.84 12.50 13.78 12.46 12.12 13.35 Grain peas 10.32 8.12 4.05 10.01 7.87 3.93 Salt 0.41 0.41 0.41 0.39 0.39 0.39 Stabilised lard 0.41 0.00 0.00 0.39 0.00 0.00 Vitamins and minerals 21.31 1.31 1.32 1.01 1.01 1.02 Proximate composition and nutritive value, % DM DM, % 87.17 87.61 88.05 87.08 87.08 88.09 Crude protein 17.76 16.59 18.43 20.92 18.66 18.30 Neutral detergent fibre 24.29 22.62 25.42 29.82 26.56 28.29 Acid detergent fibre 12.30 15.89 18.99 14.69 15.24 16.83 Acid detergent lignin 4.14 4.19 5.45 3.09 3.13 3.43 Sugar and starch 37.10 29.42 21.80 36.07 36.07 20.49 Ether extract 3.42 2.31 1.71 2.63 1.85 1.43 Ash 4.82 6.44 7.50 6.50 7.47 8.64 Calcium 0.42 0.80 1.02 0.60 0.96 1.27 Phosphorus 0.39 0.34 0.37 0.48 0.41 0.39 Gross energy, kcal/g DM 4.56 4.44 4.42 4.37 4.31 4.25 Feed units for milk, UFL/kg 0.98 0.98 0.97 0.98 0.98 0.96 Protein digestible in the intestine (PDI) 10.45 10.87 11.29 10.42 10.42 11.42 1 Control, diet based on commercial concentrates plus alfalfa hay; DOP40, diet based on concentrates with 40% of cereals replaced by dehydrated orange pulp (DOP) plus alfalfa hay; DOP80, diet based on concentrates with 80% of cereals replaced by DOP plus alfalfa hay; 2Nutral cabras LD granulado, Cargill®, Barcelona, Spain. Animals 2021,11, 2601 4 of 15 Goats were allowed ad libitum access to water and were fed once daily in the mornings. Each group’s daily food intake was calculated by subtracting the orts (uneaten food) from the amount of food offered. On average, goats were fed 0.4 kg of alfalfa hay and 1.88 kg (early lactation, until 60 d, see Guzmán et al. [ 7 ]) or 1.81 kg (mid-lactation, until 120 d) or 1.57 kg (end lactation, until 180 d) of concentrate per animal daily. After weaning, the total average intake per goat in each diet group was determined in early (DM was 2.04, 2.00 and 1.98 kg/d; crude protein was 0.36, 0.33 and 0.36 kg/d; and gross energy was 9.28, 8.90 and 8.74 Mcal/d in the CD, DOP40 and DOP80 groups, respectively), mid- (DM was 1.92, 1.92 and 1.89 kg/d; crude protein was 0.34, 0.32 and 0.35 kg/d; and gross energy was 8.76, 8.53 and 8.35 Mcal/d in the CD, DOP40 and DOP80 groups, respectively) and late lactation (DM was 1.78, 1.76 and 1.75 kg/d; crude protein was 0.32, 0.29 and 0.32 kg/d; and gross energy was 8.14, 7.83 and 7.75 Mcal/d in the CD, DOP40 and DOP80 groups, respectively). After weaning and coinciding with the test-day milk yield recordings, LW and BCS were recorded for all animals (early lactation, see Guzmán et al. [ 7 ]; mid-lactation, at 90 ± 5 and 120 ±5 days postpartum; end lactation, at 150 ±5 and 180 ±5 days postpartum). After weaning the kids, the dams were milked once a day (at 09:00) in a 12-stall Casse System milking parlour; individual recorder jars were used to measure the volume of milk produced. A repeated measures design was used for recording milk yield from each animal; test-day yields were recorded in early (see Guzmán et al. [ 7 ]), mid- (at 90 ± 5 and 120 ± 5 days postpartum) and end of lactation (at 150 ± 5 and 180 ± 5 days postpartum). The total production at 180 days postpartum was calculated according to the A4 method of the International Committee for Animal Recording [ 9 ]. Representative samples (aliquots from each animal to determine milk traits) were taken from the volumetric flask of the parlour during machine milking carried out at 120 ± 5 (mid-lactation) and 180 ± 5 (end lactation) days postpartum. The aliquots were placed in 50 mL plastic bottles with preservative (Azidiol, Panreac Química, Barcelona, Spain). Samples were refrigerated and immediately sent to the laboratory for analysis. During the last month of lactation (150 to 180 days), blood from each animal (n= 10 for each diet treatment) was collected aseptically from the left jugular vein in fasting animals in the morning and poured into tubes containing lithium heparin. After centrifugation at 2300×gfor 30 min, the plasma was frozen at −20 ◦C until analysis. 2.2. Goats and Experimental Procedure (Experiment 2) Three months after partum (mid-lactation), six animals from each experimental group (CD, DOP40 and DOP80) were selected, according to their LW, BCS and milk production, for inclusion in a nutrient digestibility trial. For four days, these goats were individually housed in metabolic cages in the same stable with the other goats (from which they were separated by a fence) to mirror the conditions of the other animals as closely as possible and to provide visual, auditory and olfactory contact, to achieve better animal welfare [ 10 ]. On the first and fourth days, animals were weighed and the BCS was estimated [8]. Animals were fed once a day (9:00 h), and water was offered ad libitum. Refusals were weighed daily to determine the individual intake. The quantity of diet supplied was calculated in order to allow approximately 15% refusal. Samples of the supplied diet (2%) and refusals (30%) for each goat were collected daily, weighed and stored at 4 ◦ C. At the end of the four experimental days, the samples were pooled and homogenised for later laboratory analyses. The faeces of each goat were collected once each day at 9:00 h, weighed, and an aliquot (20%) was kept in plastic bags at − 20 ◦ C for later analysis of apparent digestibility. Ammonia loss through volatilisation was prevented by adding 20 mL 10% HCl (v/v) daily to the urine collecting receptacles. The volume and weight of urine from each animal was recorded daily, and aliquots (10%) were stored at − 20 ◦ C for later analysis of the energy and total N content, to determine the energy and nitrogen balances, respectively, and to measure purine derivative (PD) and creatinine concentrations. Before the analysis, frozen faecal and urine samples of each goat were defrosted, pooled and homogenised. Animals 2021,11, 2601 5 of 15 The goats were milked once a day using a portable milking machine (Mayfra, 4211, Valdelafuente, León, Spain), the individual milk yield was recorded, and an aliquot (10%) was stored at 4 ◦ C. At the end of the fourth experimental day, milk samples were pooled, homogenised and stored at −20 ◦C until analysis. On the last digestibility trial day, approximately 50 mL of rumen content was collected from each animal before the morning feeding, using an oral probe attached to a vacuum pump and strained through a nylon membrane (400 µ m; Fisher Scientific S.L., Madrid, Spain) as described in Ramos-Morales et al. [ 11 ]. Two aliquots (1 mL) were taken and stored at − 20 ◦ C for, respectively, volatile fatty acids (VFA) and ammonia N (N-NH3) analyses. 2.3. Chemical Analyses of Feed, Faeces, Urine, Rumen Content, Milk and Blood Apparent nutrient digestibility was determined from corresponding intakes and losses in faeces. Nitrogen and energy balances were obtained, accounting for N and gross energy losses in urine, faeces, and milk and energy lost in methane. Before analysis, the feed (experiments 1 and 2) and refusal (experiment 2) samples were oven-dried, and the faecal samples (experiment 2) were freeze-dried, and then all the samples were ground using a Wiley mill with a 1 mm screen. AOAC [ 12 ] methods were used to determine dry matter (DM, method 934.01), ash (method 942.05), ether extract (method 920.39) and N (method 984.13) content in the samples. Total N was determined by the Kjeldahl procedure and converted to crude protein (CP) by multiplying by a factor of 6.25. The analyses of neutral detergent fibre (NDF) and acid detergent fibre (ADF) were conducted according to Van Soest et al. [ 13 ]. Amylase was not used in the analysis of NDF, and both NDF and ADF were expressed as exclusive of residual ash. Acid detergent lignin (ADL) was determined through the solubilisation of cellulose with 72% sulphuric acid. Calcium and phosphorus content was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES Jobin Yvon Ultima 2, Longjumeau, France), according to the manufacturer’s instructions. The gross energy (GE) content was determined using an adiabatic calorimeter (model AC600, LECO Corporation, St. Joseph, MI, USA), according to the manufacturer’s instructions. Sugar and starch, the feed units for milk (UFL) and digestible protein in the small intestine (PDI) were calculated using Feed Ration Balancer software. In experiment 2, the methane output was calculated as in Aguilera [ 14 ] as 10.32% of digestible energy. In the urine samples, DM (weight in 6 g), ash (weight in 6 g), CP (weight in 10 mL) and GE (weight in 4 mL) were analysed following the same methods listed above. The PD and creatinine in the urine and VFA and N-NH 3 analyses in the rumen content were performed following the corresponding procedures described by Arco-Pérez et al. [15]. In experiment 1, dry matter, protein, fat and lactose contents of milk were estimated by near-infrared spectroscopy (NIR) as described by Delgado-Pertíñez et al. [ 16 ], while somatic cell count (SCC, cells/mL) was measured by flow cytometry, using a Fossomatic Electronic Cell Counter [ 17 ]. In experiment 2, milk protein N content was calculated as the difference between total and non-protein N in milk (NPMN). Milk total N content was determined using the Dumas method (AOAC method 990.03), while the NPMN was analysed in samples of milk filtrates after precipitation with 15% (w/v) trichloroacetic acid solution [15]. In experiment 1, every blood parameter was measured using specific kits according to Tschuor et al. [ 18 ] and as described previously by Guzmán et al. [ 7 ]. The following analytes were determined: total proteins, albumin, total triglycerides, cholesterol, glucose, urea nitrogen, creatinine, total bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, creatine kinase (CK), amylase, phosphorus, total calcium, magnesium, sodium, potassium and chloride concentration. Animals 2021,11, 2601 6 of 15 2.4. Economic Analysis Profit was calculated using the following expression: total income − (feed costs + all other costs). A comparative analysis between the three groups’ diets was performed after expressing profit in three different and complementary ways: EUR/goat, EUR/day and EUR/litre of milk. Total income in each of the three groups was calculated by multiplying total milk production over the entire lactation period by the average sale price of the milk. This price was obtained from goat’s milk sales data published weekly by the Andalusian Regional Government’s Ministry of Agriculture and Fishing (Spain) from January 2019 to September 2020 [ 19 ]. The total feed costs throughout lactation were calculated by multiplying the feed inputs provided to each experimental group by their current market prices. Feed input prices were supplied by the Cargill Animal Nutrition company, while orange pulp pellet prices were furnished by Cítricos del Andévalo, S.A (Huelva, Spain). Other activity cost data (labour, animal health and energy) were provided by Cabrandalucía Federation, an organisation for the main goat breeding associations in the Spanish region of Andalusia. 2.5. Data Treatment and Statistical Analysis Goats’ weight, BCSs and daily milk yield recorded in each stage of lactation (mid, at 90 ± 5 and 120 ± 5 days postpartum; late, at 150 ± 5 and 180 ± 5 days postpartum) were analysed using the repeated measures procedure. The model included the fixed between-subjects factors, dietary treatment (CD, DOP40 or DOP80) and prolificacy (single or double birth); the fixed within-subjects factor, month of lactation (repeated measures); and the interactions between these factors. For simplification, the results for the factor, month of lactation, in both repeated measures analyses have not been presented in this paper. The data for total milk yield from birth to 180 days postpartum and composition parameters of milk samples taken in each stage of lactation (mid, at 120 ± 5 days postpartum; late, at 180 ± 5 days postpartum) were analysed using a factorial model that included dietary treatment and prolificacy and the interactions between these factors as fixed effects. Plasma biochemical parameters were analysed using a factorial model that included dietary treatment and prolificacy and the interactions between these factors as fixed effects. For experiment 2, intake, digestibility, N and energy balance and rumen fermentation parameters were analysed by ANOVA, using the GLM (including the diet offered to the animals as a fixed factor). The data analysed were the average data obtained from the four days of confinement in the metabolic cages. In all the statistical analyses, the individual goats were considered experimental units and the significance level was set at p ≤ 0.05. However, if 0.05 < p ≤ 0.10, a tendency for differences was defined. Tukey’s honestly significant difference (HSD) test was used where appropriate for pairwise comparisons of means. Statistical analyses were performed using IBM SPSS Statistics for Windows (version 25.0; IBM Corp., Armonk, NY, USA). 3. Results 3.1. Body Weight and Milk Yield and Composition Milk yield patterns and composition and the LW and BCS of goats during the entire lactation period, according to the treatment group, are presented in Table 2and Figure 1. Live weight and BCS were similar for all three diets in mid- (40.9 kg and 2.76 on average, respectively) and late lactation (42.3 kg and 2.82 on average, respectively). Different diets did not change any milk yield variables examined (p> 0.05) (average daily milk yield in mid- and late lactation and total yield at 180 days were 1.29 L/day, 1.09 L/day and 253.2 L, respectively). Similar results were obtained for gross milk composition, although in late lactation, a trend (p< 0.10) was found towards a higher percentage of fat in the control and DOP40 diets than in the DOP80 diet, and a higher percentage of lactose in the DOP diets than in control diet. Milk yield was reduced at the end of the lactation (Figure 1), Animals 2021,11, 2601 7 of 15 while the concentration of the variables related to the composition increased throughout the experiment. Table 2. Milk performance during the entire lactation period of goats fed the experimental diets. Item 3Diet (D) 1Prolificacy (PR) SEM p2 Control DOP40 DOP80 Single Twins D PR No. of goats 14 16 14 23 21 BW in mid-lactation, kg 40.6 42.5 42.2 42.6 41.1 0.61 ns ns BCS in mid-lactation 2.73 2.80 2.77 2.81 2.72 0.03 ns ns BW in late lactation, kg 40.9 43.3 43.8 41.6 43.8 0.76 ns † BCS in late lactation 2.75 2.78 2.93 2.80 2.84 0.04 ns ns Milk yield (180 d), L 252.6 252.7 254.6 219.1 292.4 12.8 ns ** Daily milk yield in mid-lactation, L/d 1.34 1.27 1.28 1.09 1.52 0.08 ns ** Daily milk yield in late lactation, L/d 1.17 1.01 1.10 0.87 1.32 0.07 ns ** DM in mid-lactation, % 12.2 12.3 12.4 12.4 12.2 0.11 ns ns DM in late lactation, % 13.8 14.0 13.1 13.8 13.5 0.20 ns ns Crude protein in mid-lactation, % 3.20 3.18 3.30 3.17 3.27 0.04 ns ns Crude protein in mid-lactation, g/d 41.8 37.8 40.7 33.3 47.4 2.33 ns ** Crude protein in late lactation, % 4.32 4.05 3.98 4.03 4.17 0.11 ns ns Crude protein in late lactation, g/d 50.6 42.5 45.6 32.3 54.0 3.13 ns *** Fat in mid-lactation, % 3.85 4.02 4.00 4.04 3.90 0.08 ns ns Fat in mid-lactation, g/d 51.3 48.0 48.6 42.4 56.6 2.73 ns * Fat in late lactation, % 4.83 4.72 4.02 4.61 4.43 0.16 † ns Fat in late lactation, g/d 55.7 47.2 45.5 37.8 57.6 3.86 ns ** Lactose in mid-lactation, % 4.43 4.43 4.39 4.46 4.38 0.04 ns ns Lactose in late lactation, % 4.15 4.52 4.42 4.47 4.30 0.06 † ns LSCC in mid-lactation, cell/mL 5.64 5.28 5.54 5.47 5.48 0.08 ns ns LSCC in late lactation, cell/mL 5.78 5.35 5.58 5.62 5.45 0.09 ns ns 1 control, diet based on commercial concentrates plus alfalfa hay; DOP40, diet based on concentrates with 40% of cereals replaced by dehydrated orange pulp (DOP) plus alfalfa hay; DOP80, diet based on concentrates with 80% of cereals replaced by DOP plus alfalfa hay; 2 statistical probability for comparisons: ns, not significant (p> 0.05); † ,p ≤ 0.10; *, p ≤ 0.05; **, p< 0.01; ***, p< 0.001; no significant interactions between these factors were noted (p> 0.05).; 3BW, body weight; BCS, body condition score; LSCC: Log10 somatic cell count. Animals 2021, 11, x. https://doi.org/10.3390/xxxxx www.mdpi.com/journal/animals (a) (b) Figure 1. Changes throughout the lactation period (means ± SE) in milk yield (a) and body weight (b) due to dam diet treatments: control diet based on commercial concentrates plus alfalfa hay, diet based on concentrates with 40% of cereals replaced by dried orange pulp (DOP) plus alfalfa hay and diet based on concentrates with 80% of cereals replaced by DOP plus alfalfa hay. 3.2. Intake, Rumen Fermentation, Apparent Nutrient Digestibility, and Protein and Energy Balance. Figure 1. Changes throughout the lactation period (means ± SE) in milk yield ( a ) and body weight ( b ) due to dam diet treatments: control diet based on commercial concentrates plus alfalfa hay, diet based on concentrates with 40% of cereals replaced by dried orange pulp (DOP) plus alfalfa hay and diet based on concentrates with 80% of cereals replaced by DOP plus alfalfa hay. Animals 2021,11, 2601 8 of 15 3.2. Nutrient Utilisation and Ruminal Fermentation The effects of the experimental diets on the nutrient intake and apparent digestibility during the metabolic cage trial are shown in Table 3. The intake of DM, OM, NDF and LAD did not differ among groups. The ether extract intake decreased significantly (p< 0.01) and the CP intake tended (p< 0.10) to decrease as the proportion of DOP increased. The ADF intake was higher (p< 0.05) for DOP80 than the control diet, while this diet showed higher and lower intake (p< 0.01), respectively, for hemicellulose and cellulose. The apparent digestibility of crude fat was lower (p<0.05) as the DOP content increased in the diet, and CP digestibility was lower (p< 0.01) for the DOP diets. Lower (p< 0.01) digestibility of ADF and cellulose was found in animals fed the control diet, which, in contrast, showed higher (p< 0.01) digestibility of hemicellulose than DOP80. Table 3. Effects of experimental diets 1on nutrients intake and apparent digestibility. Item Diet 1 SEM p2 Control n= 6 DOP40 n= 6 DOP80 n= 6 Intake (g/day) Dry matter 1668 1591 1465 51.4 ns Organic matter 1609 1514 1394 48.5 ns Ether extract 50.9a 33.1b 22.2c 3.07 ** Crude protein 290 235 233 11.5 † Neutral detergent fibre 467 398 407 13.4 ns Acid detergent fibre 177b 219ab 253a 9.91 * Acid detergent lignin 52.3 50.8 55.3 2.41 ns Hemicellulose 290a 179b 154b 15.3 ** Cellulose 119b 168a 198a 9.07 ** Apparent digestibility (g/kg) Dry matter 763 784 749 3.65 ns Organic matter 781 804 772 5.95 ns Ether extract 908a 871b 763c 15.6 * Crude protein 775a 715b 705b 10.6 ** Neutral detergent fibre 517 572 539 13.9 ns Acid detergent fibre 327b 449a 456a 34.7 ** Hemicellulose 739a 722ab 671b 11.8 ** Cellulose 737b 846a 875a 17.3 ** Means with different letters (a, b, c) within each row differ significantly (p ≤ 0.05); 1 control, diet based on commercial concentrates plus alfalfa hay; DOP40, diet based on concentrates with 40% of cereals replaced by dehydrated orange pulp (DOP) plus alfalfa hay; DOP80, diet based on concentrates with 80% of cereals replaced by DOP plus alfalfa hay; 2 statistical probability for comparisons: ns, not significant (p> 0.05); †, p≤0.10; *, p≤0.05; **, p< 0.01. The effects of experimental diets on the rumen fermentation parameters and purine derivates in urine are shown in Table 4. Apart from a tendency (p< 0.1) of the butyrate to be lower for DP80 than the control diet and purine derivates in the urine to be higher in the former diet, there were no differences related to creatinine in urine, total VFA concentration, the individual proportions of the different VFAs or ammonia N in the rumen. Table 5shows the impact of experimental diets on BW, energy and N balance as indicators of feed efficiency utilisation. Both BW and energy utilisation parameters (referred to BW) were not affected by the introduction of DOP. However, digestible N ( p< 0.05 ) and N retention (p< 0.01) and, consequently, N balance (p< 0.01) were negatively affected by the introduction of DOP. Values for both the digestible N/intake N and the N balance/digestible N were significantly (p< 0.01) lower for DOP80. Only N balance/digestible N was lower for DOP40. However, milk N relative to both N digestibility and N intake was not affected by the treatment. The milk protein N/N balance rate was ( p< 0.01 ) increased by DOP80. In addition, the digestible energy rate and the metabolisable energy as a function of energy intake were significantly (p< 0.05) lower for the DOP80 diet than for the DOP40 diet, but the latter was not different from the control diet for those parameters. Animals 2021,11, 2601 9 of 15 Table 4. Effects of experimental diets 1 on the rumen fermentation parameters and purine derivates in urine. Item 3 Diet 1 SEM p2 Control n= 6 DOP40 n= 6 DOP80 n= 6 Total VFA (mM) 73.8 80.9 78.1 8.3 ns mol/100 mol Acetate 63.7 62.0 64.5 1.1 ns Propionate 16.9 17.5 18.6 1.8 ns Isobutyrate 0.508 0.224 0.732 0.116 ns Butyrate 16.9ab 18.7a 14.1b 0.7 † Isovalerate 1.36 0.985 1.62 0.22 ns Valerate 0.502 0.610 0.553 0.082 ns Acetate/propionate 4.24 4.33 4.20 0.54 ns N-NH3, mg/L 288 280 299 22.1 ns Purine derivates, µmol/kg BW0.75 573b 573b 963a 75 † Creatinine, µmol/kg BW0.75 427 412 492 54 ns Means with different letters (a, b, c) within each row differ significantly (p ≤ 0.05); 1 control, diet based on commercial concentrates plus alfalfa hay; DOP40, diet based on concentrates with 40% of cereals replaced by dehydrated orange pulp (DOP) plus alfalfa hay; DOP80, diet based on concentrates with 80% of cereals replaced by DOP plus alfalfa hay; 2 statistical probability for comparisons: ns, not significant (p> 0.05); † ,p ≤ 0.10. 3 VFA, volatile fatty acids; BW, body weight. Table 5. Metabolic weight (BW 0.75 ), nitrogen and energy utilisation and feed efficiency in dairy goats fed the experimental diets . Item Diet 1 SEM p2 Control n= 6 DOP40 n= 6 DOP80 n= 6 BW0.75 (kg) 17.1 16.1 16.9 0.33 ns BCS 2.83 2.79 2.79 0.07 ns g/kg of BW0.75 Digestible N 32.98a 1.67b 1.67b 0.072 * N balance 40.990a 0.765b 0.609c 0.035 ** Retained N 50.507a 0.336b 0.102c 0.075 ** N utilisation (%) Digestible N/intake N 77.5a 71.5b 71.2b 1.03 ** N balance/digestible N 47.1a 42.3.1b 40.3c 2.14 ** Milk protein N/digestible N 21.0 22.9 27.6 1.40 ns Milk protein N/N balance 45.3a 58.3a 70.6b 4.16 ** Milk protein N/milk total N 91.1b 91.0b 88.9a 0.320 * Milk protein N/intake N 16.1 16.5 19.6 0.970 ns Energy utilisation, MJ/kg of BW0.75 Energy intake 2.21 2.19 1.93 0.076 ns Faecal energy 0.523 0.479 0.488 0.021 ns Urine energy 0.054 0.051 0.057 0.005 ns Milk energy 0.174 0.191 0.185 0.005 ns Digestible energy 61.69 1.71 1.44 0.061 ns Methane energy 70.174 0.177 0.149 0.006 ns ME 81.46 1.49 1.24 0.051 ns Energy utilisation, % Digestible energy/energy intake 76.5ab 78.3a 74.4b 0.57 * Milk energy/digestible energy 18.0 17.8 19.8 0.95 ns Milk energy/ME 20.8 20.6 23.1 1.08 ns ME/energy intake 66.2ab 67.8a 63.6b 0.61 * ME/digestible energy 86.5 86.7 85.5 0.36 ns Means with different letters (a, b, c) within each row differ significantly (p ≤ 0.05); 1 control, diet based on commercial concentrates plus alfalfa hay; DOP40, diet based on concentrates with 40% of cereals replaced by dehydrated orange pulp (DOP) plus alfalfa hay; DOP80, diet based on concentrates with 80% of cereals replaced by DOP plus alfalfa hay; 2statistical probability for comparisons: ns, not significant (p> 0.05); *, p ≤ 0.05; **, p< 0.01; 3 digestible N = intake N—faecal N; 4 nitrogen balance = digestible N—urine N; 5 retained N = N balance—milk total N; 6 digestible energy = energy intake—faecal energy; 7 methane energy = methane output calculated from Aguilera [14] as 10.32% of digestible energy; 8ME = digestible energy—urine energy—methane energy.