Long-term effect of selection for litter size and feeding programme on the performance of reproductive rabbit does 2. Lactation and growing period

Abstract

AbstractA total of 166 crossbred does were used to study the possible long-term effect of two types of crossbred does (H1v.H2, old and current generations, respectively) from the cross of different generations of lines selected for litter size, the use of a rearing programme based on a low-energy diet, and the administration of a high-energy diet during reproductive life, on the performance and body condition of lactating rabbit does and their litters until slaughter. The body condition of the reproductive rabbit does increased in the successive cycles to the fourth parturition, being maintained from this moment on. Animals more selected for litter size at weaning presented a greater food intake (+3%;P<0·05) and milk yield (+6%;P<0·05) during the first 21 days of lactation, which could be related to greater maternal aptitude. The difference in the weight of pups at slaughter time (+24 g for H2 respect to H1 pups) was one third lower than that expected from the generation response of the paternal line (0·45 g/day), perhaps related to the different enteropathy incidence depending on the genetic type. The use of a high-energy diet during the reproduction period increased the milk yield (+22%;P<0·05) of does, as the growth (+16 g at weaning day;P<0·05) and survival index (+2%;P<0·05) of the litters during lactation, but could produce a more sudden weaning of pups as a consequence of their lower pre-weaning food intake (−42%;P<0·05), which has been related with a greater health risk index during the growing period (+4·2%;P<0·05). Reproductive does given a high fibre diet during the rearing period (from 3 kg live weight to 28th day of the first pregnancy) reached parturition with a higher live weight than does that received a moderate energy diet restricted during this same period (+142 g;P<0·05). All other parameters controlled for the lactating does and their litters were not affected by the type of diet received during the rearing period. Females that were not effectively mated at first AI (11 dayspost partum) showed a greater increase in their perirenal fat thickness between partum and the 11th day of lactation than those lactating females that showed an effective mating (+0·22v.+0·37 mm, respectively;P<0·05).