Reproductive performance of early-weaned female swine according to their estrus profile and frequency of artificial insemination

Abstract

We determined the estrus profile (weaning-to-estrus interval (WEI), estrus duration (ED), and frequency of estrus per detection period) in 184 female swine and estimated the effect of the WEI, ED and frequency of artificial insemination (AI) on farrowing rate (FR) and litter size. Estrus detection was done at 8:30 a.m. and 5:00 p.m. The WEI was categorized as short (<100 h), medium (100–120 h) and long (>120 h). The ED was categorized as short (<60 h), medium (60–72 h) and long (>72 h). Mean lactation length was 14.6 days, mean WEI was 124.5 h and mean ED was 69 h. In each weaning group, females received either one or two AI, following a breeding schedule based on the estrus profile. In single-mated females, AI was performed 36 h after the beginning of estrus. In double-mated females, the first AI was done 24 h after the beginning of estrus and the second AI occurred 12 h later. The period of estrus detection had no effect ( P>0.05) on WEI, ED, FR, total born (TB) and live born litter size (LB). Mean FR was 82.6%, mean TB was 10.0% and mean LB was 9.2%. Mean ED was shorter ( P<0.03) for females having medium and long WEI (67.0 and 65.4 h, respectively) than for those having short WEI (72.2 h). A linear regression analysis identified a weak ( R 2=0.02) but significant negative association between ED and WEI ( P=0.05). The WEI did not influence FR ( P>0.05). Total litter size for females having short WEI (9.4) was lower ( P<0.03) than for those having long WEI (10.4). Also, LB for females having medium and long WEI (9.7–9.8) was higher ( P<0.05) than for those having short WEI (8.7). AI frequency had no effect on FR ( P>0.05). TB and LB litter size were lower ( P<0.05) for single-mated females (9.6 and 9.0, respectively) than for double-mated females (10.7 and 9.6, respectively). Double AI was associated with higher subsequent litter size. However, breeding schedules based only on estrus profile may not be precise in determining ideal breeding time, since females having short WEI had the longest ED and produced the lowest litter size.