Vasectomised boars are already in use on some commercial farms for detecting and synchronising oestrus, especially in gilts. Increasing the number of matings a sow receives during oestrus has been found to increase subsequent litter size and conception rate (Reed 1982, Tilton and Cole 1982). If vaginal-uterine stimulation is the underlying cause for this reproductive improvement, then similar effects should be possible using vasectomised boars.

A total of 200 Large White/Landrace cross sows were weaned at 4 to 5 weeks and housed adjacent to mature fertile boar where physical contact was possible through a barred gate. The sows were inspected for signs of oestrus each morning and, if receptive, were given a single mating with a fertile boar. Approximately 3 hours later, alternate sows were penned with a vasectomised boar and one service was supervised. These sows remained with the vasectomised boar overnight and were then remated with the original boar. The control sows were also remated with a fertile boar, 24 hours after the first service.

From weaning to service all sows were offered 2.7 kg of a 155 g/kg crude protein, barley based sow nut. After service this was reduced to 2.2 kg per day.