Weaning-to-service interval in primiparous sows and its relationship with longevity and piglet production

Abstract

The relationship between weaning-to-service interval (WSI) in first parity sows and longevity, including lifetime piglet production until parity eight were studied. Data from 7 Thai herds, which had both purebred Landrace and Yorkshire sows in the same herd, and from 14 crossbred Thai herds, were used in the analyses. The analyses comprised 1293 Landrace, 1072 Yorkshire, and 9334 crossbred sows mated the first time between July 1992 and June 1995. Stayability variables, describing if the sow had farrowed her 2nd to 8th litter, sum of total born piglets, live born piglets, pigs weaned and litter weaning weight for each sow from parity 2 until culling or maximum until parity 8 were analysed. The statistical model included the fixed effect of WSI of first parity, breed, first lactation length and first litter weaning weight, and random effect of herd-half year combination. Sow longevity was analysed using the proportional hazards model. The stayability of purebred sows with WSI longer than 30 days was significantly lower than for sows with WSI shorter than 9 days. The stayability of crossbred sows with WSI within 5 days was significantly higher than that of other WSI groups, and was lowest for sows with WSI >30 days. Sows that returned to oestrus later than 30 days after weaning had lower lifetime production than sows that returned to oestrus within 18 days after weaning. Crossbred sows with WSI 6 days or longer had significantly ( P<0.001) higher risk of being culled than sows with WSI 0–4 days. The risk of culling for sows with WSI longer than 30 days was 1.7 times the risk for sows with a WSI of 0–4 days.