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University of Guelph,3, Guelph, Ontario, Canada N1G 2W1
Abstract
Three groups of Yorkshire sows (total of 106) were exposed to photoperiodsof light:dark (LD) 24:0, 12:12 and 0:24, respectively, from d 1 postweaning to 24 h postestrus. The onset and duration of estrus, conception rate, farrowing rate and litter size were recorded. Serum concentrations of luteinizing hormone (LH), estrogen and progesterone were measured. Sows in the LD 24:0 exhibited behavioral estrus for a longer period (P<.0001) than those in LD 12:12 (4.0 vs 2.7 d). The number of days to estrus from d 1 postweaning (5.4, 4.5 and 4.7 d, respectively), conception rate (60, 67 and 73%, respectively), farrowing rate (60, 67 and 73%, respectively) and litter size (10.6, 10.2 and 10.8, respectively) were not different (P>.05) for the three light regimens of 24:0, 12:12 and 0:24. Maximum serum levels of LH (5.4, 5.0 and 4.5 ng/ml, respectively) and estrogen (71.8, 63.3 and 60.4 pg/ml, respectively) were not different, nor were progesterone profile means (P>.05) for the sows in LD 24:0, 12:12 and 0:24. These data suagest that long photoperiods prolong manifestations of behavioral estrus in the sow.
1 This study was supported by the following: Ontario Pork Producers, Ontario Ministry of Agr. and Food and NSERC Grant #A-6247.
2 The authors wish to thank A. Lun and D. Wey for their assistance.
3 Dept. of Anim. and Poul. Sci.
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