Factors Associated with Weaning to Service Interval in the Sow

Weaning to service interval (WSI) is one important reproductive parameter in sows.Although several factors have been explored as risk factors of WSI, other factors may exist and need to be determined.The present study aimed to investigate the effects of original factors, including manual extraction of the piglet, farrowing duration, postpartum vaginal discharge duration, and stillbirth, and some already determined factors, including parity, gestation length, lactation length, and birth litter size, on WSI.Data were collected from 394 litters born from 394 mixed parity Landrace x Yorkshire sows on a farm in Vietnam.A forward linear regression was used to determine the significant risk factors for WSI.Linear regression analysis showed that parity, birth litter size, manual extraction of the piglet, farrowing duration, postpartum vaginal discharge duration, and lactation length significantly influenced the WSI.The average WSI was 6.2±2.8 days.By day 7 post weaning, about 75% of sows had been inseminated.Among the studied risk factors, manual extraction of the piglet (coefficient=0.874,P=0.003), farrowing duration (coefficient=0.235,P=0.001), and postpartum vaginal discharge duration (coefficient=0.452,P<0.001) was positively associated with WSI.By contrast, parity (coefficient=-0.294,P<0.001), birth litter size (coefficient=-0.096,P=0.022), and lactation length (coefficient=-0.1,P=0.005) negatively correlated with WSI.The results suggested WSI could be shortened via minimization of manual extraction of the piglet, reduction in farrowing duration and postpartum vaginal discharge duration, and selection of large birth litter sizes.