A note on the effects of boar presence on the performance of sows and their litters when penned as groups in late lactation

When sows and their litters were grouped 21 days after farrowing, the introduction of a boar 4 days later stimulated lactational oestrus in only 2 of the 21 sows (seven groups of three sows and litters) exposed to the boar, while none of the sows in the control groups showed lactational oestrus. The boar presence in lactation affected the subsequent weaning to first service interval. This interval was 228 days for the sows exposed to a boar and 10·0 days for the control groups, the difference approaching significance (0·05<P<0·10). None of the sows in the boar treatment groups had a weaning to oestrus interval exceeding 9 days.