A review of the factors infl uencing the post-weaning performance of primiparous and multiparous sows was discussed. Factors examined included the breed, feeding, lactation length, body mass, gilt age at first mating, backfat thickness, season of the year, as well as the hormonal stimulation of estrus in young and primiparous sows. Insuffi cient feeding during lactation and a decrease in body mass, low backfat thickness at weaning, short/insufficient lactation, inadequate time of mating and a high environment temperature all had negative influences on the time between weaning and fi rst re-mating of primiparous sows. Contradictory views over the ideal age at first mating of gilts and the impacts on their future fertility have been expressed in the literature. The hormonal induction of estrus in primiparous sows by PG600 at various points before weaning, at weaning or aft er weaning affects the productivity of sows during future parities in complex ways.

Key words: weaning-to-estrus interval, weaning-to-service interval, weaning-to-conception interval, fertility of sows