Effect of selection for litter size and feeding programme on the performance of young rabbit females during rearing and first pregnancy

A total of 166 crossbred young female rabbits were used to study the effect of two types of crossbred does (H1 v. H2, old and current generations, respectively) from the cross of different generations of maternal lines selected for litter size, the use of a feeding programme based on a low energy rearing diet (F) and the presentation of a highenergy diet pre-partum (E) on the performance of young rabbit females until their first parturition and on the main litter traits at first kindling. Perirenal fat was thicker at the age of 3 months for H2 than for H1 does, but this difference disappeared at the first insemination (4·5 months). H2 does had a significantly larger total number and number of live pups at birth ( + 2·06 live pups) than H1, higher than expected ( + 1·06). As this greater foetal growth was obtained for a similar energy intake of does, possible differences may exist in partitioning and/or efficiencies of dietary and body energies in favour of foetal growth as the genetic propensity for litter size increased. The use of a low-energy diet significantly reduced the growth of does during the rearing period (-294 g), but they showed a greater compensatory growth during the first 4 weeks of gestation ( + 79 g) as a consequence of their higher energy intake, without any retardation in their reproductive development. Does receiving diet F until 28th day of gestation showed a significantly greater pre-partum energy intake and their number of pups born alive was lower (-1·3 pups). Finally, the litters of females receiving diet E pre-partum and during lactation had lower mortality during the 1st week (26·9 v. 42·9% dead pups) and throughout lactation than those receiving a moderate energy diet.