Interval to estrus in sows and performance of pigs after alteration of litter size during late lactation.

The effects of altering litter size during the 5 days before weaning on interval to estrus of sows and postweaning performance of pigs were examined. Litters averaged 8.3 +/- .7 pigs from parturition until 5 days before weaning. Litters were then adjusted so that sows (five per group) nursed small- (three pigs), average- (eight pigs) or large-sized (13 to 14 pigs) litters during the last 5 days of lactation. Weaning occurred 27.4 +/- .7 days postpartum. Interval from weaning to estrus (days) and duration of estrus (hours) for sows that weaned small-, average- and large- sized litters averaged 1.1 +/- .4 and 38 +/- 4, 4.1 +/- .4 and 60 +/- 4, an 4.0 +/- .4 and 61 +/- 4, respectively. Interval to estrus and to ovulation and duration of estrus were decreased (P less than .01) in sows that nursed only three pigs before weaning. Pigs weaned from foster sows weighed less (P less than .05) at weaning than pigs weaned from their dams. However, by 3 weeks after weaning, body weights were similar. Body weight at weaning and at 3 weeks postweaning and average daily gains during the 3 weeks after weaning were similar for pigs weaned from small-, average- and large-sized litters. Reducing the litter size before weaning resulted in earlier postweaning estrus and ovulation and had no adverse effects on the performance of weanling pigs.