Growth, body state and breeding performance in gilts and primiparous sows.

Optimizing gilt management is a critical point to improve breeding herd efficiency. This review describes the effects of growth rate (GR) and body state at onset of puberty stimulation or at first mating on gilt puberty attainment, productivity and sow longevity. Traditional management practices should be re-evaluated with attention to different modern genotypes. It is difficult to discern the real effects of age, weight, backfat depth and estrus number at first insemination on longevity and reproductive performance, because these variables affect one another. GR interacts with age at boar exposure to influence age at puberty. Higher lifetime GR gilts (>700 g/d) attain puberty earlier and have a lower anoestrus rate. If gilts attain a target weight (135-150 kg), are adapted to herd health status and have at least one previously recorded estrus, they can be inseminated. Overweight at first breeding and throughout gestation should be avoided. There is no advantage in breeding gilts heavier than 150 kg; at first farrowing the target weight is 180-185 kg. Piglet production at first parity may be increased in gilts with a high GR but the number of stillborn piglets can also be increased. The culling rate over 3 parities for locomotion problems, which is one of the major risk factors for reduced herd retention rate, can be increased in overweight gilts at first breeding (>150-170 kg).