The Duration of Farrowing in Relation to the Reproductive Performance of Yorkshire Sows.

Records for 212 attended farrowings by 38 Yorkshire sows were examined. Eighty per cent of the farrowings were less than six hours, 18 per cent between six and 12 hours and two per cent between 12 and 17 hours duration. There appeared to be no marked relationship between the duration of farrowing and the size of litter. In spite of a higher stillbirth rate in males, there were more male (52.3 per cent) than female piglets born alive. As the time taken to farrow increased from within 1-3 hours to more than eight hours, the percentage of stillborn piglets and the percentage of litters with stillbirths increased to 10.5 from 2.4 and to 61.1 from 18.2 per cent respectively.Twenty-nine per cent of the litters were farrowed on the 114th day of gestation. As the gestation period lengthened to 117 days or more, from 113 days or less, there were corresponding increases in the duration of farrowing and the incidence of stillbirths, and a decrease in litter size.A need to investigate the use of hormones to control parturition in sows was suggested.