The modern genetically-improved female pig reaches first mating with low levels of back fat compared to the female bred in previous decades. Increasingly too, gilts have been bred at younger ages and lower weights and the effects of these management changes are unclear. It has been questioned whether the modern gilt is under greater physiological stress especially when subjected to low feeding levels, which could influence reproductive efficiency. The objectives of the trial reported here were to compare the reproductive performance of gilts given different feeding regimes during rearing and pregnancy in order to produce a range in body weight and back fat.

The trial was designed as a 2 x 3 factorial experiment. Gilts from a Large White x Landrace crisscross breeding programme, blocked for genotype, were first allocated to one of two treatments from 10 to 25 weeks of age. Gilts were group housed and fed on a age-based scale rising to either 2.25 kg/d (L) or 2.70 kg/d (H). At 25 weeks of age, gilts with defects of teats or gait were discarded.