Observations were made on a commercial herd of female pigs (sows) where a managemental system was employed which enabled sows to be served during lactation. The system involved grouping between 2 and 8 sows together with their litters about 3 weeks post partum. The sows were fed ad libitum from grouping, and the piglets had ready access to creep food. After one day a male pig was introduced to the group. No exogenous hormone therapy was used.
Results from 39 batches, comprising 180 sows, suggested that sows kept under these conditions will exhibit oestrus, and conceive during lactation with a high degree of predictability. Lactational oestrus was shown by all sows and conception to first service was 84·9%. The number of days between grouping and oestrus, and parturition and oestrus, were 11·15 ±0·28 and 35·53 ±0·47 respectively. Litter size and performance did not appear to be adversely affected by the concurrent lactation and pregnancy, either at the present or subsequent parturition. The average farrowing interval of 153 days allowed a performance of 2·35 litters/sow per year, and, with 9·47 piglets weaned/litter, a productivity of 22 piglets/sow per year.