Impact of an extended photoperiod in farrowing houses onthe performance and behaviour of sows and their litters

M. P. Lachance1,2, J. P. Laforest2, N. Devillers1, A. Laperriere3, and C. Farmer1,4

1Agriculture and Agri-Food Canada, Dairy and Swine R & D Centre, P.O. Box 90, Sherbrooke, Quebec, CanadaJ1M 1Z3; 2Departement des Sciences Animales, Faculte des Sciences de l’agriculture et de l’alimentation,

Universite Laval, Quebec, Quebec, Canada G1V 0A6; and 3Laboratoire des Technologies de l’Energie,Institut de recherche d’Hydro-Quebec, Shawinigan, Quebec, Canada G9N 7N5.

Received 7 December 2009, accepted 19 March 2010.

Lachance, M. P., Laforest, J. P., Devillers, N., Laperriere, A. and Farmer, C. 2010. Impact of an extended photoperiod in

farrowing houses on the performance and behaviour of sows and their litters. Can. J. Anim. Sci. 90: 311�319. The effects of anextended photoperiod around parturition and throughout lactation on performances of primiparous sows and their pigletswere studied. Sows were assigned to two light regimens: (1) standard (CTL, n�28), 8 h of daily light from day 112 ofgestation until day 23 of lactation; and (2) extended (TRT, n�26), 23 h of daily light from day 112 of gestation to day 4of lactation and 16 h thereafter. Colostrum intake was estimated based on a 24-h piglet weight gain starting at the end offarrowing. Piglets were weighed on days 4, 7, 14, 21 (weaning on day 23), 35 and 56. On days 4 and 21 of lactation, milkand blood samples were obtained. Behaviour was recorded on days 3 and 20. Piglet feed intakes were noted post-weaninguntil day 56. The TRT sows had lower concentrations of melatonin than the CTL sows on day 4 (PB0.05), but prolactinconcentrations, milk composition and colostrum intake by piglets were unaffected by treatment (P�0.1). Litter growthduring lactation was unaffected (P�0.1), but TRT piglets consumed less feed between 23 and 34 d of age (PB0.05) andweighed less on day 35 (PB0.05). The TRT piglets were more active than CTL piglets on day 3 of lactation only (PB0.05).Increasing the period of daily light in the farrowing house did not improve the performance of primiparous sows and theirpiglets.

Key words: Behaviour, growth, lactation, photoperiod, piglet, sow

Lachance, M. P., Laforest, J. P., Devillers, N., Laperriere, A. et Farmer, C. 2010. Impact d’une photoperiode prolongee en

maternite sur les performances et le comportement des truies et de leurs porcelets. Can. J. Anim. Sci. 90: 311�319. L’effetd’une photoperiode prolongee a la mise bas et en lactation sur les performances de truies primipares et de leurs porcelets aete etudie. Des truies ont ete assignees a deux traitements lumineux, soit: (1) Standard (CTL, n�28), 8 h de lumiere parjour du jour 112 de gestation au jour 23 de lactation; et (2) Prolonge (TRT, n�26), 23 h de lumiere par jour du jour 112 degestation au jour 4 de lactation et 16 h de lumiere par la suite. La prise de colostrum a ete estimee en utilisant le gain depoids des porcelets dans les 24 h suivant la fin de la mise bas. Les porcelets ont ete peses aux jours 4, 7, 14, 21 (sevrage aujour 23), 35 et 56. Aux jours 4 et 21 de lactation, des echantillons de lait et de sang ont ete recueillis. Le comportement a eteenregistre aux jours 3 et 20. La consommation alimentaire des porcelets a ete notee post-sevrage jusqu’au jour 56. Lestruies TRT avaient des concentrations moindres de melatonine au jour 4 de lactation (PB0,05). Les concentrationsde prolactine, la composition du lait et la prise de colostrum par les porcelets n’ont pas ete affectees par la photoperiode(P�0,1). La croissance des porcelets a la mamelle etait similaire pour les deux groupes (P�0,1), mais la prise alimentairedes porcelets TRT des jours 23 a 34 (PB0,05) ainsi que leur poids au jour 35 (PB0,05), etaient moindres que ceux desporcelets CTL. Les porcelets TRT etaient plus actifs au jour 3 de lactation (PB0,05). L’augmentation de la periode declarte par jour en maternite n’a pas ameliore les performances zootechniques des truies primipares ni celles de leursporcelets.

Mots Cles: Comportement, croissance, lactation, photoperiode, porcelet, truie

Newborn piglets are very vulnerable because approxi-mately 10% die before weaning (Weary et al. 1998)and two important causes of death are crushing andsavaging by the dam. At farrowing, 10 to 15% of giltsshow aggressiveness towards their offspring (Chen et al.2008), and the use of an extended photoperiod (24 hinstead of 8 h of daylight) during farrowing decreased the

percentage of gilts that fatally savaged their piglets(Harris and Gonyou 2003). Sow milk yield is crucialfor the growth of piglets both pre- and post-weaning(Kavanagh et al. 1997) and there are indications thatchanges in photoperiod regimen could be used as a toolto positively influence sow lactation performances.Indeed, sows that were subjected to 16 h of daily lightthroughout lactation produced more milk than thoseunder 8 h of light (Mabry et al. 1982). Furthermore,piglets that were subjected to 16 h of light while nursingwere heavier at weaning than those under 8 h of light

4To whom correspondence should be addressed (e-mail:chantal.farmer@agr.gc.ca).

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(Mabry et al. 1982, 1983; Stevenson et al. 1983). Incontrast, other studies reported no increase in weaningweights with 16 h of daily light instead of 8 h duringlactation (Greenberg and Mahone 1982; Gooneratneand Thacker 1990). It is apparent that photoperiodicchanges in farrowing houses could be an interestingavenue to improve the performance of sows and theirpiglets. However, the light intensity needs to be wellcharacterized to allow proper comparison (Mutton1987). Indeed, McGlone et al. (1988) stated that studieson the effect of photoperiod could not be well interpretedbecause of the lack of characterization of the light used.Furthermore, there is no information on the possibleeffects of an extended photoperiod on nursing behaviourand activity of sows and piglets to ensure that welfare isnot affected. The present study was therefore conductedto determine if extending the photoperiod both duringfarrowing and throughout lactation can decrease theincidence of neonatal mortality, and improve the growthof piglets via an increase in sow milk yield. The possibleeffects of this treatment on the behaviour of sows andtheir piglets were also investigated and a detailedcharacterization of light intensity was performed.

MATERIALS AND METHODS

Animals and TreatmentsFifty-four Yorkshire � Landrace gilts were inseminatedwith semen from a pool of Duroc boars. Gilts weresubjected to 12 h of light daily (0600 to 1800) frommating to day 111 of gestation and were then randomlyassigned to two light regimens: (1) standard (CTL, n�28) consisting of 8 h of light (0730 to 1530) daily fromday 112 of gestation until day 23 of lactation, and; (2)extended (TRT, n�26) consisting of 23 h of light (0000to 2300) from day 112 of gestation until day 4 oflactation and 16 h (0730 to 2330) of daily light for theremainder of lactation (weaning on day 23). Theseprimiparous sows were housed in individual stalls(0.6�2.1 m) during gestation and were transferred tofarrowing crates on day 112 of gestation. All sows weretransferred to another farrowing room on day 4 oflactation, approximately 72 h after the end of farrowing,to ensure that all animals were subjected to the samestress since TRT sows needed to be transferred due tothe change in photoperiod occurring on this day.Farrowings took place from February to July 2008and there were equal numbers of sows from each groupfarrowing during each month.Light emissions were quantified using a luxmeter

LI-250 Light Meter (Li-Cor, Inc., Lincoln, NE), whichwas linked to a photometric sensor Licor 210SA (Li-Cor, Inc., Lincoln, NE). Each farrowing room consistedof one centre aisle with three farrowing crates on eachside. In the centre aisle, there were three fluorescentlights on the ceiling, one between each pair of farrowingcrates. Ceramic heat lamps were used instead ofstandard heat lamps in the farrowing crates to ensure

there was no source of visible light during the darkphase. There were two heat lamps in each crate. Atfarrowing, one was on the side of the sow and the otherbehind the sow. On day 2, the lamp behind the sow wasmoved to the side of the crate where there was no heatlamp. Light emissions were measured at eye level of thesow (30.5 cm from the floor) at the same 21 strategicpoints in all farrowing rooms. In the centre aisle, threepoints were used, namely, under the middle of eachfluorescent light. Light was also quantified at threepoints in each crate: in the front, under the side heatlamp and at the back of the crate. Average light intensitywas 197917, 238917, and 176921 lx in the centre aisleunder the front, middle and back fluorescents, respec-tively. In front of the crates, there was an average of5995 lx. Under the side heat lamps, light intensity was10996 lx and behind the sow, it was 4496 lx. At eachof these points, when there were no heat lamps, therewas an approximate increase of 3 lx in light intensity.There were no outdoor windows in farrowing roomsand all door windows were covered to block any sourceof light. Red lights (7 watts, Emerald lighting Canada,Toronto, ON) were placed on the ceiling to permit videorecording during the dark phase, and they were alwaysturned on, even when not recording.During gestation, gilts received a commercial feed

containing 12% CP, 12.65 MJ DE kg�1 and 0.63%total lysine. From days 1 to 99 of gestation, giltsreceived one daily meal of 2.05 kg and from days 100to 112 of gestation this was increased to 3.05 kg. Fromday 113 of gestation until farrowing, sows were fed twoequals meals of a commercial diet containing 13% CP,13.85 MJ DE kg�1 and 0.9% total lysine, totalling3.05 kg d�1. On the day of farrowing, gilts received 1 kgof this diet and from day 2 to weaning, they were fed thesame diet ad libitum. Feed refusals were weighed dailythroughout lactation to measure feed intakes. Backfatthickness of all sows was measured ultrasonically at thelast rib on days 4 and 21 of lactation (Scanmatic SM�1,Medimatic, Hellerup, Denmark) and body weights ofsows were recorded on day 112 of gestation, day 4 oflactation and at weaning. The interval from weaning tooestrus was noted.No creep feed was distributed to piglets during

lactation and they had no access to the sow feeder.Colostrum intake was estimated using a 24-h weightgain of piglets after birth. Piglets were weighed at 212952 min after birth and again exactly 24 h after the firstweighing. Piglets that were sick, had splayleg or weighedless than 900 g were not used for these weights. Littersize was standardized to 1091 pigs on day 2 oflactation. Piglets were weighed on days 4, 7, 14, 21, 35and 56. After weaning, each litter was housed in apen (1.9 m�1.9 m) containing one feeder with threeopenings, and litter sizes for TRT and CTL were 10.8and 10.6, respectively (SEM�0.1, P�0.1). All pigletswere subjected to 12 h of daily light (from 0600 to 1800).Three commercial diets were subsequently fed to piglets

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ad libitum. The first diet, containing 20% CP, 15.25 MJDE kg�1 and 1.4% lysine, was provided to piglets untilthey had all received an average of 1.5 kg of the diet.The second diet, containing 18% CP, 14.8 MJ DE kg�1

and 1.3% lysine, was then given to piglets until they hadall received an average of 5 kg of this diet. The last diet,containing 17.5% CP, 14.3 MJ DE kg�1 and 1.1%lysine, was given to piglets until 56 d of age. Afterweaning, feed intake of piglets was noted. To do so,weight of the empty feeder was originally obtained andfeed given was weighed daily. On days 35 and 56, thetotal weight of the feeder and orts was obtained anddaily feed intake per piglet was calculated. Animals werecared for according to a recommended code of practice(Agriculture and Agri-Food Canada 1993) and proce-dures were reviewed by an Institutional Animal CareCommittee in accordance with the Canadian Council onAnimal Care.

Milk and Blood SamplingsOn days 4 and 21 of lactation, a representative milksample was obtained by collecting milk via manualexpression from the first, third and sixth mammaryglands (two from one side of the udder and one from theother side) following an i.v. injection of 20 IU ofoxytocin (20 IU mL�1, P.V.U., Victoriaville, QC).Piglets were separated from their dam for 45 min beforethe oxytocin injection. Milk was frozen at �208C untilcompositional analyses were performed. On these samedays, jugular blood samples were obtained from eachsow by venipuncture between 1000 and 1115. Bloodsamples were collected in Vacutainer

†

tubes containingEDTA (for melatonin assay) and in tubes withoutanticoagulant (for prolactin assay). Tubes with EDTAwere put on ice immediately after sampling and, within20 min, were centrifuged at 48C for 12 min at 2000�g.Plasma was recovered and kept at �208C for furtheranalysis. Tubes without anticoagulant were left at roomtemperature for 3 h, stored overnight at 48C andcentrifuged at 48C for 12 min at 2000�g the followingday. Serum was stored at �208C for subsequent assays.

Milk CompositionWhole milk was used to determine dry matter, protein,fat and lactose contents. Dry matter was measuredaccording to a validated method using forced air ovendrying [Association of Official Analytical Chemists(AOAC) 2005]. Protein content was determined witha LECO analyzer (LECO FP-428, LECO Corporation,St-Joseph, MI) and fat was measured using an estab-lished ether extraction method (AOAC 2005). Lactosewas measured by a colorimetric method using acommercial kit (Megazyme International Ireland Ltd.,Bray Business Park, Bray, Co. Wicklow, Ireland) andintra- and inter-assay CV were 0.17 and 0.89%,respectively.

Hormone AssaysConcentrations of prolactin were determined witha previously described RIA (Robert et al. 1989).The radioinert prolactin was purchased from A. F.Parlow (U.S. National Hormone and Peptide Program,Harbor-UCLA Medical Centre, Torrence, CA).The first antibody to prolactin was purchased fromResearch Products International Corp. (Mt. Prospect,IL). Parallelism of a pool of serum from lactating sowswas demonstrated in 100 to 200 mL of sample. Averagerecovery, calculated by addition of various doses ofradioinert hormone to 50 mL of a pooled sample, was101.0%. Sensitivity of the prolactin assay was1.5 ngmL�1. Six samples of a representative pool ofserum were carried in duplicates in all assays in order tocalculate CV. The intra- and inter-assay CV were 3.96and 4.40%, respectively. Melatonin was measured usinga RIA commercial kit (Rocky Mountain Diagnostic,Colorado Springs, CO) which was validated withplasma from lactating sows. Parallelism of a pool ofplasma was demonstrated in 200 to 250 mL. Averagerecovery, calculated by addition of 20 mL of standards(3 and 10 pg mL�1 of melatonin) to 200 mL of a pooledsample, was 94.5%. Sensitivity of the melatonin assaywas 4 pg mL�1. Three samples of a representative poolof plasma were carried in duplicates in all assays tocalculate CV. The intra- and inter-assay CV were 2.91and 4.48%, respectively.

Behavioural Recordings and ObservationsBehaviour of 40 sows (20 per treatment selectedat random) and their piglets was video-recorded withOmnicast 4.3 (Genetec inc., Saint-Laurent, QC), using aprocedure similar to that of Valros et al. (2002).Recordings were made for a continuous 24 h periodon days 3 and 20 of lactation. Recordings started at1800 on day 2 of lactation and 5 min-scan samplingswere used to measure the number of active piglets inthe litter and postures of sows. The postures recordedwere: sitting, standing, lying ventrally and lying later-ally. Piglets were counted as active when they weresitting, standing or lying and active at the udder.Nursing and eating behaviours of sows were determinedusing continuous sampling. Nursing was considered asstarting when more than 50% of the piglets weremassaging the udder for 1 min. The end of nursingwas defined as when less than 50% of the piglets wereactive at the udder for 30 s or when the sow changedposition to avoid nursing. Nursings were catego-rized as productive (i.e., with milk ejection) or non-productive, as observed by the occurrence of rapidmouth movement by piglets. An eating episode startedwhen a sow had its head in the feeder for more than 10 sand it ended when the sow had its head out of the feederfor at least 1 min.

LACHANCE ET AL. * EXTENDED PHOTOPERIOD FOR LACTATING SOWS 313

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Statistical AnalysesThe MIXED procedure of the SAS Institute, Inc. (2002)was used for statistical analyses according to a one-wayfactorial design with the photoperiod treatment asa fixed factor. Repeated-in-time analyses were donefor data measured over successive days with the day �treatment interaction being included in the model.Analyses for each day were also performed separatelybecause TRT animals were subjected to differentphotoperiods on days 3�4 and 20�21. Statistical analyseswere done on the losses of weight and backfat thicknessof sows during lactation (between days 4 and 21).Mortality of piglets was analyzed using PROC LOGIS-TIC of SAS Institute, Inc. (2002). Postures of sows wereanalysed using Wilcoxon test. Statistical analyses onactivity of piglets were done using MIXED procedure ofSAS Institute, Inc. (2002), over three different periods oflight, namely: (1) when lights were on for both groups(0730 to 1530 on both days); (2) when lights were off forboth groups (day 3: 2300 to 0000 and day 20: 2330to 0730), and; (3) when both groups did not have thesame light schedule (lights on for TRT and lights offfor CTL, day 3: 1530 to 2300 and 0000 to 0730, day 20:1530 to 2330). A statistical tendency was defined as0.05BPB0.1 and P values smaller or equal to 0.05 wereconsidered significant. Results in tables and text arepresented as least squares means9SEM, except whenmentioned otherwise.

RESULTS

Sow DataWeights of sows on day 112 of gestation were similar forboth groups (P�0.1). Sow body weights decreased from197.69 to 187.2391.69 kg and backfat thickness from19.22 to 15.3190.44 mm between days 4 and 21 oflactation (PB0.001). These decreases were similar forsows from both groups (P�0.1). Average daily feedintakes of sows analyzed over the 3 wk of lactation byrepeated-in-time analysis were not affected by treatment(P�0.1) and there was a week effect (PB0.001), withsows eating 2.54, 4.77 and 6.27 kg d�1 (SEM�0.23 kg d�1) of feed on weeks 1, 2 and 3 of lactation,respectively.The repeated-in-time analysis showed no effect of

treatment on any of the milk components (P�0.1)but there were day effects (Table 1). Fat, dry matterand protein contents decreased as lactation progressed(PB0.001), whereas lactose increased (PB0.001).Concentrations of melatonin and prolactin in sow bloodare shown in Table 2. The repeated-in-time analysisindicated no treatment effect on concentrations ofmelatonin (P�0.1). However, separate day-by-dayanalyses showed that circulating concentrationsof melatonin were lower in TRT than CTL sows onday 4 of lactation (PB0.05) but were similar acrosstreatments on day 20 (P�0.1). There was also a dayeffect, with values being lower on day 4 than on day 21

of lactation (PB0.001). Prolactin concentrations wereunaffected by treatment overall (P�0.1) and there wasno day � treatment interaction (P�0.1). Values weregreater on day 4 than on day 21 of lactation (PB0.001).The interval from weaning to first oestrus was unaf-fected by the extended photoperiod (TRT�9.69,CTL�8.53, SEM�1.71 days, P�0.1).

Piglet DataThe incidence of mortality from birth to 56 d of age didnot differ between TRT and CTL piglets (means forboth groups were: days 1�2�2.32%, days 3�4�1.34%,days 5�23�1.08%, and days 24�56�0.90%, P�0.1).Only three CTL sows, and none of the TRT sows,showed aggressive behaviour towards their offspring.Piglet birth weights were similar across treatments(TRT�1.42, CTL�1.45, SEM�0.01 kg, P�0.1) andpiglet colostrum intake, as estimated by weight gain,was also unaffected by treatments (TRT�78.92,CTL�81.39, SEM�12.10 g, P�0.1).Weights of piglets are shown in Table 3. Weights

of piglets throughout lactation were unaffected bytreatments (P�0.1) but there was a day � treatmentinteraction indicating that TRT piglets weighed less thanCTL piglets post-weaning on day 35 of age (PB0.05)

Table 1. Milk composition on days 4 and 21 of lactation for sows

subjected to an extended (TRT; 23 h of light from day 112 of gestation to

day 4 of lactation and 16 h of light, thereafter) or standard (CTL; 8 h of

light, from day 112 of gestation to day 23 of lactation) photoperiod

TRT CTL Effects

Milkcomponent

Day4

Day21

Day4

Day21 SEM Trt Day

Trt�Day

Dry matter (%) 21.77 19.02 21.21 19.02 0.53 NS * NSFat (%) 9.75 7.13 9.15 7.13 0.49 NS * NSProtein (%) 6.27 5.48 6.17 5.48 0.13 NS * NSLactose (%) 4.19 5.07 4.31 5.07 0.09 NS * NS

*PB0.05.

Table 2. Circulating concentrations of prolactin and melatonin on days 4

and 21 of lactation for sows subjected to an extended (TRT; 23 h of light

from day 112 of gestation to day 4 of lactation and 16 h of light,

thereafter) or standard (CTL; 8 h of light, from day 112 of gestation to

day 23 of lactation) photoperiod

Hormone TRT CTL SEM

Plasma melatoninz (pg mL�1)Day 4 6.76b 9.52a 0.88Day 21 19.47 22.85 2.31

Serum prolactinz (ng mL�1)Day 4 20.53 22.98 1.42Day 21 12.11 12.16 0.76

zDay effect (PB0.05).a, b Means in the same row with different letters differ (PB0.05).

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but that on day 56, weight was again similar for pigletsfrom both groups (P�0.1). The TRT piglets consumedless feed than CTL piglets from weaning to day 34(TRT�231.74, CTL�256.86, SEM�8.20 g d�1

piglet�1, PB0.05), yet, from days 35 to 56, feed intakewas similar for piglets from both groups (TRT�683.77,CTL�695.55, SEM�16.39 g, d�1, P�0.1).

Behavioural Data

Sow BehaviourThe percentage of time that sows spent in variouspostures is shown in Table 4. Sows from both groupsspent the same proportion of time sitting, lying laterallyor lying ventrally on both days of lactation (P�0.1).The CTL sows tended to spend more time standing thanthe TRT sows on day 20 of lactation (PB0.1), yet, onday 3, sows from both groups spent the same proportionof time standing (P�0.1).Over all days of lactation, CTL sows tended to have

more eating episodes than TRT sows (TRT�5.65,CTL�7.08, SEM�0.51, PB0.1) and spent more totaltime eating (TRT�35.73, CTL�43.47, SEM�2.40min, PB0.05). There was also a day effect, withnumber of eating episodes or total time eating increasingas lactation progressed (PB0.001) but there wasno day � treatment interaction (P�0.1).

Activity of PigletsThe repeated-in-time analysis showed that TRT pigletstended to be more active than CTL piglets (TRT�35.76, CTL�34.16, SEM�0.56% of piglets beingactive, PB0.1). Piglets were also more active on day20 than on day 3 of lactation (day 3�33.67, day 20�36.56, SEM�0.54%, PB0.001). There was no day �treatment interaction. The activity patterns of TRT andCTL piglets on days 3 and 20 of lactation are shown inFig. 1, and CTL and TRT piglets did not have the samepattern of activity on day 20. Indeed, CTL piglets hadtwo major periods of activity, one in the morning andone in the afternoon (before lights were turned off),

whereas TRT piglets had the same period of activity inthe morning, but the second period of activity started inthe afternoon, around 1400 and persisted as long as thelights were on, namely, until 2330.During the light period, a day � treatment interac-

tion showed that treatment did not affect activity levelof piglets on day 3 (P�0.1), whereas CTL piglets weremore active than TRT piglets on day 20 of lactation(CTL�54.78, TRT�42.68, SEM�1.63% of pigletsbeing active, PB0.001). During the daily period whenlights were off for both groups, there was also a day �treatment interaction; treatments had no effect onactivity level on day 3 (P�0.1), but CTL piglets weremore active than TRT piglets on day 20 (CTL�26.60,TRT�21.08, SEM�0.60% of piglets being active, PB0.001). Finally, during the daily period when the lightschedule differed between the two treatments (i.e., lightswere off for CTL and on for TRT piglets), TRT pigletsshowed an increased activity on both days 3 (CTL�30.49, TRT�33.86, SEM�0.93, PB0.5) and 20(CTL�26.88, TRT�47.26, SEM�1.22, PB0.001) oflactation.

Nursing BehaviourThe repeated-in-time analysis showed that TRT pigletstended to spend more time nursing than CTL piglets(TRT�248.45, CTL�228.36, SEM�7.45 min 24�1 h,PB0.1) and there was a day effect, with piglets fromboth treatments spending more time nursing on day3 than on day 20 of lactation (PB0.05). Dataon nursing behaviour of piglets when considering eitherall nursings or productive nursings only (with milkejection) are shown in Table 5. The total numberof nursings (i.e., productive and non-productive) perday was unaffected by treatments (P�0.1) and there

Table 3. Weights (kg) of piglets subjected to an extended (TRT; 23 h of

light from birth to day 4 of lactation and 16 h of light until weaning on

day 23) or standard (CTL; 8 h of light from birth to weaning)

photoperiod throughout lactation

Day of agez TRT CTL SEM

1 1.47 1.52 0.032 1.55 1.57 0.034 1.85 1.89 0.047 2.47 2.52 0.0614 4.39 4.48 0.1221 6.40 6.57 0.1535 8.95b 9.46a 0.1856 17.76 18.11 0.31

zDay effect (PB0.05).a, b Means in the same row with different letters differ (PB0.05).

Table 4. Percentage of time spent in various postures on days 3 and 20 of

lactation for sows subjected to an extended (TRT; 23 h of light from day

112 of gestation to day 4 of lactation and 16 h of light, thereafter) or

standard (CTL; 8 h of light, from day 112 of gestation to day 23 of

lactation) photoperiod (mean 9 standard error)

Posture TRT CTL

SittingDay 3 1.5390.41 2.3790.50Day 20 4.0890.59 4.0890.65

StandingDay 3 2.0390.45 2.5090.42Day 20 7.0590.46b 8.0990.64a

Lying laterallyDay 3 90.2291.48 87.1791.58Day 20 75.5391.24 71.0392.06

Lying ventrallyDay 3 6.2291.17 7.9691.36Day 20 13.3491.17 16.8192.03

a, b Means in the same row with different letters tend to differ(PB0.1).

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was no day effect (P�0.1) or day�treatment interac-tion (P�0.1). Mean duration of all nursings waslonger on day 3 than on day 20 of lactation (PB0.05)and mean intervals between all nursings tended tobe greater for CTL than TRT litters (PB0.1) on bothdays of lactation. The percentage of total nursingsended by piglets was unaffected by treatment (P�0.1),but piglets ended more nursings on day 3 than onday 20 of lactation (90.9792.09 vs. 59.4392.83%,mean9standard error, for days 3 and 20, respectively,PB0.05).

The number of productive nursings per day wasunaffected by the photoperiod (P�0.1), but therewere more productive nursings on day 20 than on day3 of lactation (PB0.05). The mean duration of produc-tive nursings was not affected by treatment (P�0.1),but was longer on day 3 than on day 20 (PB0.05).The intervals between productive nursings tended tobe shorter on day 20 than on day 3 (PB0.1) and theseparate analyses for each day showed that, on day3 only, the intervals were shorter for TRT than for CTLlitters (PB0.05).

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Fig. 1. Percentages of piglets being active on days 3 and 20 of age, when subjected to a standard (CTL; 8 h of light from birth toweaning) or an extended (TRT; 23 h of light, from birth to day 4 of lactation and 16 h of light until weaning, on day 23) photoperiodfor: (A) CTL piglets on day 3, (B) CTL piglets on day 20, (C) TRT piglets on day 3 and (D) TRT piglets on day 20. Black and whitehorizontal bars represent photoperiod duration.

Table 5. Nursing behaviour of piglets on days 3 and 20 of age, when subjected to an extended (TRT; 23 h of light, from birth to day 4 of lactation and 16 h

of light until weaning on day 23) or standard (CTL; 8 h of light from birth to weaning) photoperiod throughout lactation

TRT CTL Effects

Nursing behaviour Day 3 Day 20 Day 3 Day 20 SEM Trt Day Trt � Day

Total number of nursings 41.25 42.45 39.23 39.50 1.31 NS NS NSMean duration of all nursings (min) 6.46 5.54 6.05 5.75 0.24 NS * NSMean interval between all nursings (min) 28.98 28.79 31.77 31.77 1.16 $ NS NS

Number of productive nursings 33.00 34.25 31.01 33.25 0.92 NS * NSMean duration of productive nursings (min) 6.76 5.88 6.20 5.90 0.27 NS * NSMean interval between productive nursings (min) 37.25b 36.54 41.40a 38.29 1.33 * $ NS

$PB0.1 and *PB0.05.a, b Means in the same row with different letters differ, based on separate analyses done for each day (PB0.05).

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DISCUSSIONThe current lack of effect of an extended photoperiodin the farrowing house on piglet growth contradictsearlier findings of Mabry et al. (1982), but corroboratesfindings of Greenberg and Mahone (1982) andGooneratne and Thacker (1990), comparing 16 with8 h of daily light. Light intensity could be a factorinvolved in this discrepancy, since sows in the study ofMabry et al. (1982) were subjected to 400�500 lx andeven though it is not stated where light intensity wasmeasured, it is likely that it was greater than that in thepresent study, since the maximal average intensity was238 lx in the centre aisle. Average light intensity at soweye level in Gooneratne and Thacker’s study (1990) wasapproximately 180 lx and it was not measured byGreenberg and Mahone (1982). Stevenson et al. (1983)also showed that suckling piglets subjected to 16 insteadof 8 h of daily light were heavier at weaning, but therewas a confounding effect with light intensity. Indeed,light intensity 0.3 m above the floor varied between 20and 54 lx for control sows and between 32 and 366 lx fortreated sows. On the other hand, Mutton et al. (1987)reported no effect of an increase from 50 to 700 lx onpiglet weaning weights. Parity is a factor that could bethought of as having an impact on the response of sowsand piglets to photoperiod. Yet, this does not appearto be the case, because Mabry et al. (1982, 1983) andStevenson et al. (1983) used both primiparous andmultiparous sows in their studies and did not see adifference in piglet growth rate in response to photo-period depending on the parity.The lack of treatment effect on milk composition

largely corroborates results of Mabry et al. (1983), whonoted that the only milk component affected by photo-period in sows was total solids, which increased from15.9 to 16.8% with 16 instead of 8 h of daily light.It is likely that any effects of photoperiod during

lactation could be exerted via endocrine or behaviouralcomponents. Indeed, Mabry et al. (1982) suggested thatthe increase in piglet weights subjected to 16 h of dailylight could be explained by an increase in the numberof nursings and in concentrations of prolactin in thesow; however, these were not measured. The essentialrole of prolactin for sow milk production is known(Farmer et al. 1998) and the lack of treatment effecton circulating concentrations of prolactin thereforecorroborates the similar piglet growth rates for thetwo groups. The fact that circulating concentrations ofprolactin were unaffected by the increase in daily lightperiod corroborates findings from Kraeling et al. (1983)and Niekamp et al. (2006) in sows, and from Diekmanand Hoagland (1983) in gilts. However, piglet growthrate was not measured in these sow studies, so it doesnot preclude the fact that prolactin concentrations couldhave been altered in studies where photoperiod did havea positive effect on sow milk yield. It is not knownwhether other metabolic hormones important forgalactopoiesis, such as IGF-I, were altered by treatment;

yet, if that were the case, one would have expected to seedifferences in body weight or body condition of sowsreflecting changes in energy status.Melatonin is another hormone that could likely

be affected by photoperiod since it is secreted duringdarkness (McConnell and Ellendorff 1987; Green et al.1996). However, there is some contradiction as towhether there is a circadian rhythm of melatoninsecretion in swine. Some authors did not find a cleardiurnal rhythm (McConnell and Ellendorff 1987;Minton et al. 1989; Diekman et al. 1992; Bollingeret al. 1997), whereas recent studies did report such acycle (Green et al. 1996; Andersson et al. 2000; Tastet al. 2001). The lower circulating concentrations ofmelatonin in TRT sows on day 4 of lactation couldlikely be explained by the fact that they were exposed toonly 1 h of darkness from day 112 of gestation until day4 of lactation. Yet, no difference in melatonin was seenat the end of lactation, when sows were subjected toeither 16 or 8 h of daily light. This suggests that durationof the period of darkness is an important effector ofmelatonin secretion, but it could also be that the timeelapsed between the end of darkness and blood samplingcould be important. To the best of our knowledge, thepresent findings are the first report on the effect oflactation day on melatonin concentrations in sows, andthe drastic increase between days 4 and 21 of lactationsuggests that daylight is not the sole factor affectingconcentrations of melatonin in lactating sows. The highconcentrations of progesterone and oestrogen aroundfarrowing could have an impact on melatonin secretion.Indeed, San Martin and Touitou (2000) demonstratedthat, in rats, perfusion of the pineal gland withprogesterone decreased the release of melatonin duringthe light phase. It was suggested that progesterone playsa role in keeping concentrations of melatonin low duringthe light phase. In contrast, San Martin et al. (1996)demonstrated that 17b-oestradiol and testosteronemarkedly increased the release of melatonin, and theseeffects were more pronounced in the dark than inthe light phase. It is evident that the mechanism ofaction by which gonadal hormones affect melatoninrelease needs further investigation.Only three sows were aggressive towards their

offspring at farrowing, and they were all in the CTLgroup, representing 10% of the CTL sows. This wouldsupport findings of Harris and Gonyou (2003), wheresows under a 24 h light regimen were less aggressivetowards their piglets than sows subjected to 8 h of dailylight (2.7% vs. 3.6%). However, there was no decreasein pre-weaning mortality with an extended photoperiodin the present study, thereby confirming the results ofStevenson et al. (1983), where an increase from 8 to 16 hof daily light did not affect survival rate of pigletsto weaning. It is important to mention that mortalityrates in the controlled environment of the present studywere very low, varying from 0.9 to 2.3%, and thereforenot representative of what is seen in commercial herds.

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The fact that litters were standardized may havecontributed to this lower mortality rate. Weary et al.(1998) indeed reported that 10.2% of piglets die beforeweaning. It is not known whether the effect of treatmentwould have been more prominent should mortality rateshave been greater.To the best of our knowledge the current study is the

first to provide information on the impact of anextended photoperiod on the behaviour of sows andpiglets. As previously demonstrated (Blackshaw et al.1994; Farmer et al. 2001; Van der Brand et al. 2004),sows spent less time lying as lactation advanced. Sowpostures were also unaffected by treatment so thatincreasing daily light did not have a negative impacton sow behaviour. In fact, TRT sows tended to spendmore time lying than CTL sows on day 20 of lactation.The lack of effect on sow posture is important since themain cause of pre-weaning mortality is crushing, whichis largely due to sow posture changes (Weary et al.1998), yet posture changes per se were not measured inthe present trial.Even though CTL sows tended to spend more time

with their head in the feeder and to have more eatingepisodes than TRT sows on day 3 of lactation, the lackof effect on daily feed intake indicated that sows onlyput their head in the feeder more often without actuallyeating more feed. This contradicts findings of Prunieret al. (1994), who reported that sows subjected to 16 h ofdaily light lost less weight than sows subjected to 8 h oflight. These authors suggested a direct effect of lightduration on sow feed intake, yet, this was not measured.It is apparent that increasing the photoperiod does nothave negative effects on sow eating behaviour, butcurrent results suggest that it could not be used as atool to increase sow feed intake during lactation.In terms of nursing behaviour, it is of interest to note

that even though the interval between productivenursings was lower for TRT than CTL sows on day 3of lactation, the number of productive nursings wassimilar for both groups. The decrease in the intervalsbetween productive nursings was therefore not largeenough to lead to a significant increase in number ofproductive nursings, which ties in with the unalteredgrowth of piglets throughout lactation.On day 3 of lactation, TRT piglets were more active

than CTL piglets. Lay et al. (1999) also showed thatweaned piglets subjected to 24 h of daily light were moreactive between 1830 and 0630 than piglets subjected to12 h of daily light, and tended to be more active duringthe entire day. One could postulate that the increasedactivity level of TRT piglets, leading to greater energyexpenditure, may have masked any beneficial effect thatthe long photoperiod may have had on sow milk yield.The pattern of activity of suckling piglets also differedbetween groups. Indeed, on day 20 of lactation, CTLpiglets were more active in the afternoon whereas TRTpiglets were more active in the evening. It was previouslydemonstrated that when lights are on between 0730 and

1700, piglets in farrowing crates are more active in theafternoon (Blackshaw et al. 1994). Increasing the dailylight in the current study therefore both increased thepercentage of piglets being active, and modified theirdaily pattern of activity.The early adaptation to weaning was more difficult

for TRT than CTL piglets, as demonstrated by a lowerfeed intake from day 23 to day 34 and a lower bodyweight on day 35. This was likely due to the decrease indaily light between the farrowing room and the nurseryfrom 16 to 12 h in the TRT group compared with theCTL group, where there was an increase in daily lightfrom 8 to 12 h. Furthermore, TRT piglets likely had toalter their feeding behaviour at weaning because therewas no light during most of the period from 1600 to2330 at which time they had a high level of activityduring lactation. Nevertheless, the lack of treatmenteffect on daily feed intakes and weights of piglets on day56 suggests that they had adapted to the new photo-period by that time.In conclusion, increasing the duration of daily light

at farrowing and throughout lactation did not havebeneficial impacts on the performances of first-paritysows and their litters. The observed effects on nursingbehaviour, activity and feeding behaviour of sows andpiglets were not major enough to bring about anychanges in zootechnical parameters. It is not knownwhether the decrease from 23 to 16 h of daily light in theTRT litters somewhat hindered a possible positive effectof photoperiod, or whether a greater light intensitycould have led to a beneficial response. Neverthelessthe current lighting regime could not be recommendedin farrowing houses. The best combination of lightintensity and light duration to optimize sow and litterperformances still needs to be determined.

ACKNOWLEDGEMENTSThe authors sincerely thank L. Thibault and A. Bernier,for technical assistance, C. Corriveau, J. Deom andM. C. Triolet, for video analyses, and S. Methot forstatistical analyses, as well as the staff of the SherbrookeAAFC Swine Complex, especially M. Turcotte andE. Berube, for care and handling of the animals. Thanksto the Quebec Federation of Swine Producers and toHydro-Quebec for their financial assistance, as well as tothe ‘‘Centre d’Insemination Porcine du Quebec’’ (CIPQ)for providing the Duroc semen.

Andersson, H., Lillpers, K., Rydhmer, L. and Forsberg, M.2000. Influence of light environment and photoperiod onplasma melatonin and cortisol profiles in young domesticboars, comparing two commercial melatonin assays. Domest.Anim. Endocrinol. 19: 261�274.Association of Officicial Analytical Chemists. 2005. Officialmethods of analysis of AOAC International. 18th ed. AOACInternational, Arlington, VA.Blackshaw, J. K., Blackshaw, A. W., Thomas, F. J. and

Newman, F. W. 1994. Comparison of behaviour patterns of

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186.

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rson

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sows and litters in a farrowing crate and a farrowing pen.Appl. Anim. Behav. Sci. 39: 281�295.Bollinger, A. L., Wilson, M. E., Pusateri, A. E., Green, M. L.,

Martin, T. G. and Diekman, M. A. 1997. Lack of a nocturnalrise in serum concentrations of melatonin as gilts attainpuberty. J. Anim. Sci. 75: 1885�1892.Chen, C., Gilbert, C. L., Yang, G., Guo, Y., Segonds-Pichon,

A., Ma, J., Evans, G., Brenig, B., Sargent, C., Affara, N. and

Huang, L. 2008. Maternal infanticide in sows: Incidence andbehavioural comparisons between savaging and non-savagingsows at parturition. Appl. Anim. Behav. Sci. 109: 238�248.Diekman, M. A., Brandt, K. E., Green, M. L., Clapper, J. A.

and Malayer, J. R. 1992. Lack of a nocturnal rise of serummelatonin in prepubertal gilts. Domest. Anim. Endocrinol. 9:161�167.Diekman, M. A. and Hoagland, T. A. 1983. Influence ofsupplemental lighting during periods of increasing or decreas-ing daylength on the onset of puberty in gilts. J. Anim. Sci. 57:1235�1242.Farmer, C., Palin, M. F., Sorensen, M. T. and Robert, S. 2001.

Lactational performance, nursing and maternal behavior ofUpton-Meishan and Large White sows. Can. J. Anim. Sci. 81:487�493.Farmer, C., Robert, S. and Rushen, J. 1998. Bromocriptinegiven orally to periparturient or lactating sows inhibits milkproduction. J. Anim. Sci. 76: 750�757.Gooneratne, A. D. and Thacker, P. A. 1990. Influence of anextended photoperiod on sow and litter performance. Livest.Prod. Sci. 24: 83�88.Green, M. L., Clapper, J. A., Andres, C. J. and Diekman, M. A.

1996. Serum concentrations of melatonin in prepubertal giltsexposed to either constant or stepwise biweekly alteration inscotophase. Domest. Anim. Endocrinol. 13: 307�323.Greenberg, L. G. and Mahone, J. P. 1982. Failure of a 16 h L:8h D or an 8 h L:16 h D photoperiod to influence lactation orreproductive efficiency in sows. Can. J. Anim. Sci. 62: 141�145.Harris, M. J. and Gonyou, H. W. 2003. Savaging behaviour indomestic gilts: A study of seven commercial farms. Can. J.Anim. Sci. 83: 821�823.Kavanagh, S., Lynch, P. B., Caffrey, P. J. and Henry, W. D.

1997. The effect of pig weaning weight on post-weaningperformance and carcass traits. Proc. 6th Conference ofthe Australian Pig Science Association, Christchurch, NewZealand.Kraeling, R. R., Rampacek, G. B., Mabry, J. W., Cunningham,

F. L. and Pinkert, C. A. 1983. Serum concentrations ofpituitary and adrenal hormones in female pigs exposed totwo photoperiods. J. Anim. Sci. 57: 1243�1250.Lay, D. C., Buchanan, H. S. and Haussmann, M. F. 1999.

A note on simulating the ‘observer’ effect using constantphotoperiod on nursery pigs. Appl. Anim. Behav. Sci. 63:301�309.Mabry, J. W., Coffey, M. T. and Seerley, R. W. 1983. Acomparison of an 8- versus 16-hour photoperiod during

lactation on nursing frequency of the baby pig and maternalperformance of the sow. J. Anim. Sci. 57: 292�295.Mabry, J. W., Cunningham, F. L., Kraeling, R. R. and

Rampacek, G. B. 1982. The effect of artificially extendedphotoperiod during lactation on maternal performance of thesow. J. Anim. Sci. 54: 918�921.McConnell, S. J. and Ellendorff, F. 1987. Absence of nocturnalplasma melatonin surge under long and short artificialphotoperiods in the domestic sow. J. Pineal Res. 4: 201�210.McGlone, J. J., Stansbury, W. F., Tribble, L. F. and Morrow,

J. L. 1988. Photoperiod and heat stress influence on lactatingsow performance and photoperiod effects on nursery pigperformance. J. Anim. Sci. 66: 1915�1919.Minton, J. E., Davis, D. L. and Stevenson, J. S. 1989.

Contribution of the photoperiod to circadian variations inserum cortisol and melatonin in boars. Domest. Anim.Endocrinol. 6: 177�181.Mutton, W. J. 1987. The influence of photoperiod and lightintensity on the farrowing sow and litter. Br. Soc. Anim. Prod.11: 137�138.Niekamp, S. R., Sutherland, M. A., Dahl, G. E. and Salak-

Johnson, J. L. 2006. Photoperiod influences the immune statusof multiparous pregnant sows and their piglets. J. Anim. Sci.84: 2072�2082.Prunier, A., Dourmad, J. Y. and Etienne, M. 1994. Effect oflight regimen under various ambient temperatures on sow andlitter performance. J. Anim. Sci. 72: 1461�1466.San Martin, M., Bogdan, A. and Touitou, Y. 1996. Day-nightdifferences in the effects of gonadal hormones on melatoninrelease from perifused rat pineals. Evidence of a circadiancontrol. Steroids 61: 27�32.San Martin, M. and Touitou, Y. 2000. Progesterone inhibits, ona circadian basis, the release of melatonin by rat pinealperifusion. Steroids 65: 206�209.SAS Institute, Inc. 2002. SAS statistical analysis system.Release 9.1. SAS Institute, Inc., Cary, NC.Stevenson, J. S., Pollmann, D. S., Davis, D. L. and Murphy,

J. P. 1983. Influence of supplemental light on sow perfor-mance during and after lactation. J. Anim. Sci. 56: 1282�1286.Tast, A., Love, R. J., Evans, G., Andersson, H., Peltoniemi,

O. A. T. and Kennaway, D. J. 2001. The photophase lightintensity does not affect the scotophase melatonin response inthe domestic pig. Anim. Reprod. Sci. 65: 283�290.Valros, A. E., Rundgren, M., Spinka, M., Saloniemi, H.,

Rydhmer, L. and Algers, B. 2002. Nursing behaviour of sowsduring 5 weeks lactation and effects on piglet growth. Appl.Anim. Behav. Sci. 76: 93�104.Van den Brand, H., Schouten, W. G. P. and Kemp, B. 2004.

Maternal feed intake but not feed composition affects posturalbehaviour and nursing frequency of lactating primiparoussows. Appl. Anim. Behav. Sci. 86: 41�49.Weary, D. M., Phillips, P. A., Pajor, E. A., Fraser, D. and

Thompson, B. K. 1998. Crushing of piglets by sows: effects oflitter features, pen features and sow behaviour. Appl. Anim.Behav. Sci. 61: 103�111.

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