Reproductive performance of gilts bred on first versus third estrus.

Reproductive performance of gilts initially bred on first observed estrus was compared with that of gilts bred on third observed estrus. One-hundred and twelve Yorkshire gilts were used and 106 conceived. Conception rate to initial breeding was lower among gilts bred on first versus third observed estrus (69.6 vs 77.4%). Estrus was observed in some gilts between 140 and 149 days of age; the mean age at estrus for all gilts that were bred was 177.8 days. The mean weight at puberty was 91.7 kilograms. There was a tendency toward increased litter size at birth and weaning when breeding was delayed to third estrus, but the difference was not statistically significant. Live weight of piglets was increased in litters from sows bred initially on third estrus. The weaning-to-estrus or conception interval was not influenced by initial breeding on first or third estrus. Maintaining gilts until third observed estrus required feed and accommodation for approximately 44 additional days before breeding and resulted in 1.4 additional pigs per sow over three parities.