The effect on sow productivity of oestrus suppression following a two-day lactation

Abstract

SUMMARYSows which had lactated for 2 days were allocated either to a control group or to a group in which oestrus was delayed by the administration of 75 mg methallibure per day for 12 consecutive days, followed by an intramuscular injection of 1000 IU pregnant mare serum gonadotrophin. All sows were mated whenever they were receptive to a boar. The mean time to first mating for the control group of 12 sows was 7·3 days but the mean time to conception was 22·3 days. The corresponding figures for the 9 treated sows were 17·0 and 22·2 days. The treated sows had significantly (P < 0·025) larger litters than the control sows (11·7 v. 8·5). For those sows which conceived at the first post-weaning service, the delayed oestrus treatment increased litter size on average by more than four pigs per litter.