Sows detected in oestrus between 2 and 6 days after weaning were homogeneously distributed within three treatment groups (trios) according to parity (three to six), mean lifetime number of piglets born (9–19 piglets), pre-vious lactation length (18–24 days), number of weaned piglets (9–14 piglets), and body condition score at insemi-nation on a scale of five points (Young et al., 2004)