Analyses o body weigh pa e ns in g owing pigs: a new iew on
body weigh in pigs o equen moni o ing
A. H. S yga
1†
, K. A. Dolecheck
2
and A. R. K is ensen
1
1
Depa men o Ve e ina y and Animal Sciences, Uni e si y o Copenhagen, G ønnegå ds ej 2, DK-1870 F ede iksbe g C, Denma k;
2
Depa men o Animal and Food
Sciences, Uni e si y o Ken ucky, Lexing on, KY 40546, USA
(Recei ed 29 June 2016; Accep ed 24 May 2017)
F equen BW moni o ing o g owing pigs can be use ul o iden i ying p oduc ion (e.g. eeding), heal h and wel a e p oblems.
Howe e , in o de o cons uc a ool which will p ope ly ecognize abno mali ies in pigs’g ow h a p ecise desc ip ion o he
g ow h p ocess should be used. In his s udy we p oposed a new model o pig g ow h accoun ing o daily fluc ua ions in BW.
Body weigh measu emen s o 1710 pigs (865 gil s and 843 ba ows) o igina ing om fi e consecu i e ba ches om a Danish
comme cial a m we e collec ed. Pigs we e inse ed in o a la ge pen (maximum capaci y =400) be ween No embe 2014 and
Sep embe 2015. On a e age, each pig was obse ed o 42 days and weighed 3.6 imes a day when passing om he es ing o
eeding a ea. Al oge he , 243,160 BW measu emen s we e eco ded. A mul ile el model o pig g ow h was cons uc ed and fi ed
o a ailable da a. The BW o pigs was modeled as a quad a ic unc ion o ime. A diu nal pa e n was inco po a ed in o he model
by a cosine wa e wi h known leng h (24 h). The model included pig e ec which was defined as a andom au o eg essi e p ocess
wi h exponen ial co ela ion. Va iance o wi hin-pigs e o was assumed o inc ease wi h ime. Because only fi e ba ches we e
obse ed, i was no possible o ob ain he andom e ec o ba ch. Howe e , in o de o accoun o he ba ch e ec he model
included in e ac ions be ween ba ch and fixed pa ame e s: in e cep , ime, squa e alue o ime and cosine wa e. The gende
e ec was no significan and was emo ed om he final model. Fo all ba ches, mo ning and a e noon peaks in he equency o
isi s o he eeding a ea could be dis inguished. Acco ding o esul s, pigs we e ligh e in he mo ning and hea ie in he e ening
(minimum BW was eached a ound 1000 h and maximum a ound 2200 h). Howe e , he exac ime o ob aining maximum and
minimum BW du ing he day di e ed be ween ba ches. Pigs had access o na u al ligh and, he e o e, exis ing di e ences could
be explained by a ying dayligh le el du ing obse a ions pe iods. Because he diu nal ampli ude o pig g ow h a ied be ween
ba ches om 0.9 o 1.4 kg, BW moni o ing ools based on equen measu emen s should accoun o diu nal a ia ion in BW o
pigs. This p oposed desc ip ion o g ow h will be buil in o a moni o ing ool (a dynamic linea model) and applied o a m da a in
u u e s udies.
Keywo ds: au oma ic g ow h moni o ing, BW, diu nal pa e n, pigs
Implica ions
Body weigh is a equen ly epo ed ai in biological s udies.
Fo example, we wan o know how BW changes wi h age,
du ing a disease o a e applying a he apy. Howe e , so a
we ha e been neglec ing he ac ha BW can change also
du ing a day. We showed ha BW o pigs du ing 1 day on
a e age fluc ua es om 0.9 o e en 1.4 kg. These fluc ua ions
a e highly s a is ically significan and should be included
in ma hema ical models desc ibing g ow h. The knowledge
on BW hy hm migh be use ul in designing expe imen s,
in e p e ing esul s o de eloping moni o ing ools.
In oduc ion
I has been assumed ha he g ow h o pigs is well
desc ibed. Fo pigs obse ed du ing sho ime in e als,
g ow h has been defined simply by linea unc ions wi h he
in e cep ep esen ing ini ial BW and he slope exp essing an
inc ease in BW (To
e al
., 2005). Fo pigs obse ed o e
longe ime in e als, pe iods wi h as e and slowe g ow h
a es ha e been exp essed in he o m o Gompe z unc ions
(Niemi
e al
., 2015). Such desc ip ion o g ow h is adequa e
o adi ional BW moni o ing, which in ol es, o example,
mo ing pigs om pens o a weighing c a e on a daily, weekly
o mon hly bases. Mo e equen BW moni o ing can be
use ul o p oduc ion moni o ing as well as iden i ying heal h
†
E-mail: [email p o ec ed]
Animal
, page 1 o 8 © The Animal Conso ium 2017. This is an Open Access a icle, dis ibu ed unde he e ms o he
C ea i e Commons A ibu ion licence (h p://c ea i ecommons.o g/licenses/by/4.0/), which pe mi s un es ic ed e-use, dis ibu ion, and
ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed.
doi:10.1017/S1751731117001690
animal
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and wel a e p oblems (Co nou and K is ensen, 2013).
Howe e , o au oma ic g ow h moni o ing o be use ul, a
mo e p ecise desc ip ion o g ow h migh be necessa y.
In pa icula , diu nal g ow h pa e ns may be necessa y o
accoun o when mul iple BW measu emen s a e aken
wi hin 1 day. Män ysaa i and Män ysaa i (2015) sugges ed
ha , in dai y ca le, BW a ies h oughou he day acco ding
o udde , gu and bladde fill. Indeed, hey ound ha wice-
daily BW measu emen s om 230 dai y ca le we e an
a e age 7.3 kg lowe in he mo ning han in he a e noon.
Because bo h measu emen s we e aken a e milking, a
minimal e ec o udde fill was assumed. Ins ead, he diu nal
influence was a ibu ed o he cows ea ing mo e du ing he
day ime han du ing he nigh ime. Simila ly, mul iple ecen
s udies using au oma ically collec ed da a ha e iden ified
diu nal eeding pa e ns in pigs (Fe nández
e al
., 2011; Hoy
e al
., 2012; And e a
e al
., 2016). Al hough i is in ui i e o
hink BW o pigs migh also ollow a diu nal pa e n, no
p e ious esea ch appea s o ha e e ified ha assump ion.
This s udy is pa o la ge p ojec , aimed a designing a
ool able o ale he a me abou de e io a ion in pigs’
g ow h. In o de o ale he a me o unexpec ed changes in
g ow h, p ecise desc ip ion o g ow h on an hou ly basis has
o be known.
The main objec i e o his s udy was o desc ibe he
ela ionship be ween he BW o pigs and ime exp essed in
hou s and o e alua e he assump ion ha he BW o pigs
ollows a diu nal cyclic pa e n. In he p esen ed s udy, he
numbe o egis e ed isi s o he eeding a ea was also
in es iga ed. F equencies o isi s o he eeding a ea we e
compa ed wi h he ob ained diu nal ampli ude o pigs’g ow h.
Ma e ial and me hods
Da a om he he d
The PigIT p ojec is a s a egic esea ch alliance ounded o
imp o e wel a e and p oduc i i y in g owing pigs using
ad anced in o ma ion and communica ion echnologies
me hods (K is ensen and Jensen, 2015). The BW da a used in
his s udy was collec ed on a comme cial he d o finishing
pigs wi hin he PigIT p ojec . The he d included a finishe uni
wi h ou la ge common pens, each wi h a maximum capa-
ci y o 400 pigs. Each la ge common pen measu ed 14.0 m by
9.0 m and included a main a ea o es ing, wo eeding a eas
wi h 18 eeding poin s each, and a slaugh e collec ion a ea.
In his he d, he main a ea o each pen was sepa a ed om
he eeding a ea and he slaugh e collec ion a ea by a
weigh so ing sys em (Ag isys-Nedap, G oenlo, The Ne he -
lands, g aphically illus a ed on Figu e 1). Each ime a pig
wan ed o en e he eeding a ea i had o pass h ough he
weighing sys em. When a pig en e ed he weighing sys em,
he scale doo s closed, he pig was iden ified using an indi-
idual elec onic ea ag, weigh was eco ded and hen he
sys em di ec ed he pig o whiche e eeding a ea i was
assigned (based on weigh ). A e eeding, pigs could exi he
eeding a ea and en e he main a ea ia a one-way doo .
Al e na i ely, once he pig eached slaugh e weigh i was
au oma ically di ec ed in o he slaugh e collec ion a ea. Any
sick pigs, when iden ified by he he d ca e ake , we e mo ed
o a sec ion o sick animals.
In he s udied a m all o he pigs o igina ed om a c oss-
b ed dam (Land ace ×Yo kshi e) and a pu e b ed si e
(Du oc), which is a common combina ion in Denma k. Pigs
en e ed he la ge common pen finishe uni in mixed-sex
g oups when hey eached ~30 kg. The sex o weighed pigs
was iden ified using elec onic ea ags (gil s we e ma ked
wi h e en numbe s while ba ows we e ma ked wi h odd
numbe s). The pigs we e allowed a 5-week adap a ion pe iod
o lea n he weigh so ing sys em. Du ing ha ime, all
doo s be ween he main a ea and eeding a ea we e open.
Following he adap ion pe iod, weigh was eco ded each
ime each pig en e ed he eeding a ea un il slaugh e . In he
case ha wo pigs en e ed he scale simul aneously, BW was
no egis e ed. Fo each ba ch, BW da a we e egis e ed
om he ime o u ning on scales un il he las pigs
we e sen o slaugh e (example o all BW eco dings o
Ba ch 1 is p esen ed in Figu e 2). All pigs we e ed
ad libi um
.
Fo a de ailed desc ip ion o he eeding s a egy, see
K ogsdahl (2015).
In his s udy, BW measu emen s o pigs om Pen 1 (Ba ch 1,
Ba ch 3, Ba ch 4, Ba ch 5) and Pen 2 (Ba ch 2) we e ob ained
and analysed. Ba ches we e obse ed du ing di e en
seasons. Ba ch 1 and 2 we e obse ed du ing win e , Ba ch 3
du ing sp ing, Ba ch 4 du ing summe and Ba ch 5 in
au umn. A summa y o all BW da a used in his s udy is
p esen ed in Table 1. Al oge he , 243,160 BW measu emen s
we e collec ed om 1710 pigs. All collec ed eco ds we e
used in he analyses.
Pigs we e exposed o bo h na u al ligh (placing o doo s
and windows ma ked in Figu e 1) and a ificial ligh (24-h
lamp o e weighing scale). The a m had a combi-di use
en ila ion sys em. Tempe a u e in he p oduc ion uni was
Figu e 1 O e iew o he la ge common pen finishe uni ha da a was
collec ed om o a s udy on daily changes in pig BW whe e (A) main
a ea, (B) eeding a ea, (C) elie a ea, (D) so ing a ea, (E) weighing scale
wi h 24-h lamp, (F) doo s and (G) windows ( om K ogsdahl 2015).
S yga , Dolecheck and K is ensen
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egula ed by he sp inkle s ha we e ins alled abo e he
main, eeding and collec ing a ea and by he clima e com-
pu e . Fu he desc ip ions o animals, labo and manage-
men can be ound in K ogsdahl (2015).
Time co ec ions
In o de o p ope ly accoun o he diu nal pa e n in all
ba ches, he ime o BW measu emen s was co ec ed o
dayligh sa ing ime (DST). The DST indica o was ob ained
using he app oach o G olemund and Wickham (2011),
implemen ed in R. Time o each BW obse a ion was checked
o DST changes. I BW was obse ed du ing cen al Eu opean
summe ime, he ime o obse a ion was educed by 1 h.
Due o he aining pe iod (when pigs we e passing h ough
scales wi hou ha ing hei BW egis e ed) he fi s ini ial BW
in o ma ion was ob ained a 29 days a e inse ion in he pen.
The e o e, o his analysis, he ini ial obse a ion ime ( 0=0)
was se a 696 h (29 days) a e inse ion.
S a is ical analysis
Me hods simila o S yga and K is ensen (2016) we e used
o desc ibe he BW o pigs in he he d. The fixed pa o he
model p esen ed by S yga and K is ensen (2016) was sup-
plemen ed wi h fixed e ec s o he ampli ude and equency
o a cosine wa e (used o accoun o he diu nal pa e n
in daily BW). Due o he small numbe o obse ed ba ches
(fi e consecu i e ba ches we e ollowed), i was no possible o
es ima e he andom slope and in e cep o he ba ch e ec in
he final model. Ins ead, he fi using gene alized leas squa es
me hod was applied o ob ain a ep esen a ion o he BW o a
pa icula pig a a gi en hou . Howe e , in o de o accoun o
he a ia ion be ween ba ches, he final model was supple-
men ed wi h in e ac ions be ween ba ches and he fixed
elemen s o he model. In summa y, he ull model used in he
analyses o BW o pig
i
in ba ch
j
o e ime
was desc ibed as:
yij =ðβ0+q0jÞ+ðβ1+q1jÞ +q2j 2+ðβ2+q3jÞcosðw Þ
+ðβ3+q4jÞsinðw Þ+Aij +ϵij
Aij N0;σ2
A

;ϵij N0;σ2
 ð1Þ
in which β0;β1a e he fixed he d e ec s o in e cep and ime
while β2and β3a e fixed e ec s o he cosine wa e,
q0j;q1j;q2j;q3j;q4ja e he fixed e ec s o in e cep , ime,
squa e alue o ime and cosine wa e assumed independen
o di e en ba ches, Aij is a andom e ec o pig and ϵij is a
andom esidual. Pa ame e s β2;β3;q3jand q4jde e mine he
ampli ude and wis he leng h o he cosine wa e used o
accoun o he diu nal pa e n in daily BW. He e, wis cons an ,
does no a y wi h pig o ba ch, and was calcula ed as
w=2π=24 ( ep esen ing exac ly 1 day).
In addi ion, a gende coe ficien was es ed. The
P
- alue
o he gende coe ficien sugges ed no significan di e -
ences be ween g ow h o gil s and ba ows (
P
=0.52), and
was he e o e emo ed om he final model.
The model assumed ha he wi hin-ba ch e o s a e
allowed o be he e oscedas ic. The ollowing models
speci ying wi hin-g oup a iance we e es ed: fixed a iance,
di e en a iances pe s a um, powe o co a ia e, expo-
nen ial o co a ia e and cons an plus powe o co a ia e.
The model which success ully desc ibed he wi hin-g oup
a iance was cons an plus powe o co a ia e. This a iance
model was gi en by he equa ion:
σ2
A +σ2
=σ2
Aδ1+
jj
δ2

2
+σ2δ1+
jj
δ2

2(2)
in which σ2
Ais he a iance in animal e ec , σ2is he a iance
in measu emen e o , δ1and δ2a e cons an s o he
a iance model es ima ed om da a.
Since he BW da a consis ed o epea ed measu emen s on
he same pigs, he pig e ec was assumed o be a fi s o de
au o eg essi e p ocess wi h mean 0 and au oco ela ion ρso
ha
Aij =ρσ
A =σA; 1

Aij; 1+ωij (3)
in which ωij Nð0;ð1ρ2Þσ2
A Þ:
The obse a ions o BW o pigs we e no equally spaced in
ime. The e o e, simila o Pinhei o and Ba es (2000) we used
con inuous- ime wi hin-g oup co ela ion models, which
na u ally accommoda e he imbalance in he da a. Tes ed
co ela ion models included: linea , a ional quad a ic,
sphe ical, Gaussian and exponen ial. Simila o S yga and
K is ensen (2016), he mos adequa e wi hin-g oup co ela-
ion model o pig BW da a was ound when assuming ha
he co ela ion be ween BW measu emen s o a single pig
dec eases exponen ially wi h ime.
Table 1
Summa y o da a om fi e ba ches used in a s udy o daily pig g ow h
Inse ion No. o
No. o
To al no. o A e age no. o Ini ial mean Ini ial SD in
Ba ch da e obse a ion days
1
Gil s Ba ows BW measu emen s obse a ion (pe pig/day) BW o pigs (kg)
2
BW o pigs (kg)
2
1 25.11.2014 60 166 164 54,322 3.55 57.5 9.9
2 08.12.2014 64 165 158 51,237 3.66 62.1 8.3
3 02.03.2015 58 178 173 43,130 3.61 61.6 9.9
4 08.06.2015 58 177 178 51,700 3.38 59.9 8.0
5 15.09.2015 35
3
179 170 42,771 3.77 55.0 9.7
1
Numbe o days om u ning on he scales un il he las eco ded deli e y o pigs om gi en pen o he slaugh e house.
2
Based on he fi s eco ded obse a ion.
3
The smalle numbe o obse a ions was due o an e o in sa ing da a in he da abase.
Cyclic g ow h pa e n in pigs
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Following he app oach o Pinhei o and Ba es (2000) he
significance o e ms used in he fixed e ec model we e
es ed by he condi ional
F
- es s in he single-a gumen o m
o he ANOVA o fi ed models. The
ANOVA
me hod was
also used o es he significance o he he e oscedas ic
model. Spa ial co ela ion models we e compa ed based on
in o ma ion c i e ia s a is ics (Akaike in o ma ion c i e ion
and Bayesian in o ma ion c i e ion).
Fo da a analyses and plo ing, he R s a is ical so wa e
(R Co e Team, 2014) and nlme package (Pinhei o
e al
.,
2017) was used.
Resul s
To ge an o e iew o he collec ed da a, BW measu emen s
om he fi e ba ches we e plo ed and examined. On
a e age, each pig was obse ed o 42 days and had 3.6
egis e ed weigh s pe day. A bo h he daily and hou ly
le el, inc easing a iance be ween pigs o e ime was
e iden (Figu e 2) as p e iously iden ified by S yga and
K is ensen (2016). In addi ion, a diu nal pa e n in hou ly BW
measu emen s was iden ified as seen in Figu e 3.
G ow h model wi h diu nal pa e n
All pa ame e s desc ibing he BW o pigs om he s udied
he d ( oge he wi h 95% confidence in e als and
P
- alues
used o es ing he fixed e ec s o he model), ob ained om
he model fi , a e summa ized in Table 2.
Acco ding o he esul s, he lowes ini ial BW o pigs was
iden ified in Ba ch 2 (51 kg) while he highes was iden ified
in Ba ch 3 (60.5 kg). The he d daily gain was ~1.2 kg. The
highes daily gain was ob ained o Ba ch 2 (a ound 1.3 kg/
day) whe eas he lowes was ob ained o Ba ch 5 (a ound
1.0 kg/day). Pigs we e ligh e in he mo ning ( he minimum
o he equency wa e was ob ained a ound 1000 h) and
hea ie in he e ening ( he maximum o he equency wa e
was ob ained a ound 2200 h) (Figu e 4). Howe e , he exac
ime o ob aining maximum and minimum BW du ing he
day di e ed be ween ba ches. In his he d, daily a ia ion in
BW o pigs was ~1.2 kg. The lowes daily ampli ude in BW o
pigs was obse ed o Ba ch 5 (0.9 kg) whe eas he highes
daily ampli ude in BW was ound o Ba ch 4 (1.4 kg).
F equency o isi s o he eeding a ea
In all o he ba ches, mo ning and a e noon peaks in he
equency o isi s could be dis inguished. Howe e , o
Ba ch 3 and Ba ch 4 he mo ning eeding peak was ea lie in
he day han he o he obse ed ba ches (Figu e 5). Fo
example, 4.9% o all egis a ions o Ba ch 3 we e aken
be ween 0600 and 0659 h. Fo he same ba ch be ween
0900 and 0959 h he equency o obse a ions was 5.0%.
Con a y, o Ba ch 1 he equency o obse a ions be ween
0600 and 0659 h was only 2.3%, while be ween 0900 and
0959 h he equency inc eased o 5.3%.
Discussion
Diu nal pa e n o pig g ow h
In his s udy, he BW o pigs was modeled as a quad a ic
unc ion o ime. A diu nal pa e n was inco po a ed in o he
model by a cosine wa e wi h known leng h (24 h).
In 1938, Baldwin and Kendeigh (1938) confi med he
exis ence o daily hy hms in he BW o mul iple wild species
o bi ds. They demons a ed ha BW a ia ion o he smalle
passe ine species amoun o as much as 12% o he mean
daily BW. Howe e , his a ied wi h di e ences in ai em-
pe a u e, amoun o eeding and o he ac i i ies. Thei s udy
iden ified ha all bi ds los BW a nigh and gained BW he
ollowing day. The loss o BW du ing he nigh was explained
by lowe ai empe a u e whe eas a g adual weigh inc ease
du ing he day was due o ac i e eeding. Al hough he s udy
on daily a ia ion in BW o wild bi ds con inued (see o
example he e iew by Cla k (1979) o Macleod
e al
. (2005)),
no much a en ion has been gi en o daily a ia ion in BW o
a m animals. Daily measu emen s o a m animals a e
ob iously a easie o ob ain han hose o wild li ing spe-
cies. Howe e , especially o pigs, un il ecen imes i was
no easy o collec equen in o ma ion on indi idual BW
wi hou he need o handling animals, which was bo h ime
consuming and expensi e. One migh suspec ha o ani-
mals ha ha e cons an access o eed and a e kep in mo e
o less cons an empe a u es he daily a ia ion in BW will
Figu e 3 Body weigh measu emen s collec ed du ing he whole
a ening pe iod o selec ed pigs om pen numbe 1.
Figu e 2 Body weigh o all pigs om Ba ch 1. Each line ep esen s he
BW o an indi idual pig.
S yga , Dolecheck and K is ensen
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be small. Howe e , ecen ly, Män ysaa i and Män ysaa i
(2015) demons a ed clea diu nal changes in BW o No dic
Red cows which had eed a ailable 24 h. In hei s udy, he
a e age di e ence be ween mo ning and e ening BW o he
cow was 7.3 kg. The au ho s a e no awa e o s udies ha
ha e e alua ed he daily a ia ion in BW o pigs.
Ou esul s showed ha he ampli ude o BW fluc ua ion
was clea ly di e en be ween ba ches. I is in ui i e o sus-
pec ha he numbe o isi s du ing he day could influence
he ampli ude o BW fluc ua ions. Fo g owing–finishing
pigs, eeding pa e ns changed wi h age om sho and
equen meals o long and la ge ones (Bigelow and Houp ,
1988; Fàb ega
e al
., 2003). This was also seen in ou da a.
Pigs in Ba ch no.5 we e obse ed o ~1 mon h only and
isi ed he eeding a ea wi h he highes equency compa ed
wi h pigs om o he ba ches which we e obse ed o e
~2 mon hs. Mo e equen isi s o he eeding a ea o pigs
in Ba ch 5 esul ed in he lowes fluc ua ions in daily BW. On
he con a y, pigs om Ba ch 4, wi h he lowes a e age
numbe o weigh measu emen s we e cha ac e ized wi h
he highes a ia ion in BW du ing a day.
Nielsen
e al
. (1995) ound ha he g oup size in which
pigs we e kep influenced eeding beha io a iables, wi h
pigs kep in la ge g oups making ewe bu longe isi s o
he eede compa ed wi h smalle g oups. In ou s udy, he
ini ial size o he ba ches was simila . The size o he g oup
Table 2
Pa ame e s used o desc ibe diu nal and pe iodic changes o BW o pigs in he examined he d du ing he a ening
pe iod
1
Pa ame e
2
Symbol Value 95% confidence in e al
P
- alue
He d fixed e ec o in e cep β056.38 ± 0.78 <0.01
He d fixed e ec o ime β14.90 ×10
−2
± 1.24 ×10
−3
<0.01
He d fixed e ec o he cos wa e β257.70 ×10
−2
± 1.43 ×10
−2
<0.01
He d fixed e ec o he sin wa e β3−25.92 ×10
−2
± 1.44 ×10
−2
<0.01
In e cep ×Ba ch 2 q02 −5.22 ± 1.18 <0.01
In e cep ×Ba ch 3 q03 4.13 ± 1.09 <0.01
In e cep ×Ba ch 4 q04 1.94 ± 1.09 <0.01
In e cep ×Ba ch 5 q05 −2.53 ± 1.09 <0.01
Time ×Ba ch 2 q12 0.49 ×10
−2
± 2.14 ×10
−3
<0.01
Time ×Ba ch 3 q13 −0.26 ×10
−2
± 1.78 ×10
−3
<0.01
Time ×Ba ch 4 q14 −0.36 ×10
−2
± 1.76 ×10
−3
<0.01
Time ×Ba ch 5 q15 −0.92 ×10
−2
± 1.88 ×10
−3
<0.01
Quad a ic ime ×Ba ch 1 q21 −1.22 ×10
−6
± 9.68 ×10
−7
0.01
Quad a ic ime ×Ba ch 2 q22 −5.43 ×10
−6
± 1.16 ×10
−6
<0.01
Quad a ic ime ×Ba ch 3 q23 −6.88 ×10
−6
± 1.13 ×10
−6
0.2
Quad a ic ime ×Ba ch 4 q24 −9.29 ×10
−8
± 1.01 ×10
−6
0.8
Quad a ic ime ×Ba ch 5 q25 5.66 ×10
−6
± 1.51 ×10
−6
<0.01
Cos wa e ×Ba ch 2 q32 −0.03 ± 2.18 ×10
−2
<0.01
Cos wa e ×Ba ch 3 q33 −0.36 ± 1.16 ×10
−2
<0.01
Cos wa e ×Ba ch 4 q34 −0.01 ± 2.06 ×10
−2
0.3
Cos wa e ×Ba ch 5 q35 −0.15 ± 2.05 ×10
−2
<0.01
Sin wa e ×Ba ch 2 q42 −0.02 ± 2.18 ×10
−2
0.06
Sin wa e ×Ba ch 3 q43 −0.30 ± 2.05 ×10
−2
<0.01
Sin wa e ×Ba ch 4 q44 −0.15 ± 2.03 ×10
−2
<0.01
Sin wa e ×Ba ch 5 q45 0.10 ± 2.10 ×10
−2
<0.01
E olu ion e o σ2
A04.60 ×10
−5
± 2.29 ×10
−5
Obse a ional e o σ2
05.53 ×10
−7
± 3.61 ×10
−8
Co ela ion
3
ρ
99.57 ×10
−2
± 2.76 ×10
−4
Powe o a iance model
δ
1
0.96 ± 0.03
Cons an o a iance model
δ
2
1056.1 ± 242.29
1
BW o pig iin ba ch jo e ime was desc ibed using equa ion (1).
2
Es ima es o in e cep ×Ba ch 1, ime ×Ba ch 1, Cos wa e ×Ba ch 1 and Sin wa e ×Ba ch 1 we e equal o 0.
3
Assuming 24 h elapsed be ween measu emen s.
Figu e 4 Diu nal fluc ua ions in he BW o pigs om each ba ch
es ima ed om he de eloped model.
Cyclic g ow h pa e n in pigs
5
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was dec easing wi h ime as he ac ion o hea ies pigs was
sen o slaugh e . As he same slaugh e s a egy was
implemen ed o all ba ches, he g oup size was dec easing
a he same pace o all ba ches. The e o e, di e ences in he
numbe o isi s o he eeding a ea be ween ba ches could
mos ly be a ibu ed o di e ences in age.
The main ocus o his s udy was o desc ibe he g ow h o
pigs on an hou ly basis. Howe e , u u e s udies on he ds
using equen BW moni o ing o pigs in la ge pens could
ocus on combing beha io al da a wi h BW measu emen s.
Combining his in o ma ion would allow o s udy which
ac o s (e.g. he ini ial BW o inse ed pigs, ini ial a ia ion in
BW, e c.) influence he numbe o isi s o he eeding a ea
as well as how he numbe o isi s o he eeding a ea
influences g ow h a e in a la ge pen en i onmen .
Obse ed pa e n o isi s o he eeding a ea
D inking pa e ns a e closely co ela ed o eed consump ion
(Bigelow and Houp , 1988). The e o e, no su p isingly,
diu nal pa e ns including wo s able and dis inguished
peaks we e iden ified in he d inking beha io o g owing
pigs in he s udy by Madsen and K is ensen (2005). Those
d inking peaks (mo ning and a e noon) desc ibed by
Madsen and K is ensen (2005) coincide wi h he eeding ime
and BW peaks ound in ou s udy.
Bo h Hyun
e al
. (1997) and Young and Law ence (1994)
iden ified a single eeding peak pe day in pigs ed
ad libi um
a ~0900 h. O he esea che s ha e iden ified wo eeding
peaks pe day, one in he mo ning and one in he a e noon
(Mon gome y
e al
., 1978; Bigelow and Houp , 1988; De
Hae and Me ks, 1992). Di e ences in he numbe o eeding
peaks ha e been a ibu ed o he pho ope iod ha pigs a e
exposed o (Feddes
e al
., 1989) and he empe a u e in he
a ening uni (Villag á
e al
., 2007).
In ou s udy, pigs had access o dayligh and o cons an
a ificial ligh om a lamp ins alled abo e he scale
(Figu e 1). Pigs in na u al condi ions a e ac i e upon dayligh
(Cu is, 1937). Howe e , access o a ificial ligh could al e
hei beha io . As epo ed by Lay
e al
. (1999), pigs wi h
cons an access o ligh we e mo e ac i e be ween 1830 and
0630 h han pigs subjec ed o a 12h ligh –12 h da k cycle.
To ou bes knowledge, he e a e no s udies ha epo ed
pigs’ac i i y in a pen wi h dayligh access and a ificial ligh
illumina ing he weighing scale in he pen.
In Denma k, he a ailabili y o na u al ligh a ies acco ding
o he season o he yea . Since ba ches we e obse ed du ing
di e en seasons, di e en a ailabili y o dayligh clea ly
influenced he equency o isi s o he eeding a ea. Fo
example, pigs om Ba ch 3 we e much mo e ac i e a ound
0700hcompa edwi hpigs omBa ch1andBa ch2.
Acco ding o Villag á
e al
. (2007) i he indoo empe a-
u e is close o he he mo neu al zone (be ween 14°C and
24°C), pigs a e likely o de elop a na u al beha io wi h wo
peaks o eed consump ion and ac i i y du ing he illumi-
na ed pe iod. Howe e , Feddes
e al
. (1989) epo ed ha
changes in empe a u e on he a m migh be su ficien o
modi y eeding pa e ns o g owing pigs. They ound ha
when he indoo empe a u e cycles be ween 26°C a 0530 h
and 40°C a 1400 h, he diu nal eeding pa e n o pigs will
be di e en compa ed o a scena io wi h cons an empe a-
u e (33°C). They de e mined ha when empe a u e a ied,
eed consump ion shi ed o he cooles pa o he he mal
cycle. Mo eo e , he pe iod o highes eed in ake occu ed
ea lie in he mo ning and la e a nigh han in he cons an
Figu e 5 Pe cen age o o al isi s o he eeding a ea (BW measu emen s) in each ba ch depending on he hou o he day.
S yga , Dolecheck and K is ensen
6
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empe a u e ea men . Tempe a u e was no egis e ed in
ou s udy he e o e he possible influence o empe a u e on
he eeding pa e n could no be analysed. Gi en ha he
a m had a sys em egula ing indoo empe a u e, big
a ia ions du ing he p oduc ion cycle as epo ed in he
abo e s udies we e unlikely.
Fu u e applica ion o he model
Diu nal a ia ion o BW in pigs can find applica ion in in o ming
he a me o unexpec ed g ow h de e io a ion o whole
ba ches o pigs o pa icula indi iduals. Un il ecen ly, ob ain-
ing equen in o ma ion on BW in ol ed handling animals
(mo ing hem o scales loca ed ou side o pens) he e o e,
gaining p ecise knowledge on BW was di ficul and expensi e.
Howe e , mo e and mo e a me s a e in es ing in p ecision
li es ock echnologies, such as a weigh so ing sys em ins alled
in la ge pens. In his sys em, in o ma ion on BW da a is
collec ed on he a m when he pig is isi ing he eeding a ea.
Body weigh is a equen ly epo ed ai in biological
s udies. Fo example in pig p oduc ion, we wan o know how
BW changes wi h age (Schinckel
e al
., 2004), du ing a disease
challenge o a e applying a he apy (S yga
e al
., 2016).
Howe e , so a diu nal BW a ia ion has been neglec ed.
Acco ding o ou esul s, he di e ence be ween mo ning and
e ening BW o a pig was significan . The e o e, any equen
BW moni o ing ool aiming a de ec ing, o example, heal h o
he d managemen p oblems should accoun o he diu nal
a ia ion o BW in pigs. Mo eo e , any expe imen s in which
BW is one o he esponse a iables should be conduc ed so
ha BW is egis e ed only du ing a specific pa o he day.
The model pa ame e s ob ained in his s udy will be used
in a moni o ing ool (dynamic linea model (DLM)) based on
equen BW obse a ions. Fo an example o he applica ion
o a DLM o moni o ing g ow h o pigs, a e e ence o S yga
and K is ensen (2016) is made.
Acco ding o he ob ained esul s, pa ame e s desc ibing
diu nal a ia ion in BW should be included. Mo eo e , he
ob ained pa ame e s (e.g. he d fixed e ec s, obse a ional
and e olu ion a iance as well as au oco ela ion) will be
used o speci y a iance componen s and o se he ini ial
dis ibu ion o he pa ame e ec o in he DLM.
The season o he yea migh also influence he BW o pigs.
In Polish condi ions, Kościński
e al
. (2009) ound ha he
highes g ow h a e in pigs occu s be ween May and June.
They also demons a ed ha he weigh o 6-mon h-old pigs
plo ed by mon h o bi h ollows a cosine wa e wi h he
highes BW occu ing in pigs bo n in Feb ua y and he lowes
in pigs bo n in Augus . The e o e, season is ano he e ec
ha should be conside ed o inclusion in he model o pig
BW as mo e da a is collec ed.
Conclusions
In his pape we desc ibed a new model o pig g ow h
applied o equen BW moni o ing. In he p oposed model,
pig BW was desc ibed by he in e cep (ini ial BW), slope
(a e age daily gain du ing a ening) and a pe iodic pa e n
(diu nal fluc ua ions in BW). In he examined he d, he
diu nal ampli ude o pig g ow h anged om 0.9 o 1.4 kg.
The e o e, wi h mode n echnologies (such as au oma ic
scaling sys ems), accoun ing o daily fluc ua ions in BW
becomes necessa y. The p oposed ma hema ical model o
g ow h will be buil in o a moni o ing ool (a DLM wi h
Kalman fil e ) and applied o a m da a in u u e s udies.
Acknowledgmen s
This esea ch was suppo ed by he Danish Council o S a egic
Resea ch (The PigIT p ojec , G an numbe 11-116191). The
au ho s acknowledge The Danish Pig Resea ch Cen e and an
anonymous a me o p o iding da a and o aluable in o -
ma ion ega ding he p oduc ion uni .
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