Phenotypic and genetic parameters of birth weight and weaning weight of rabbits born from unilaterally ovariectomized and intact does

Litters from 130 does of a synthetic line were used in the experiment. The left ovary was removed before puberty in 64 of these females (ULO does). Th e offspring of the first and second parities of all the does was individual ly weighed at birth (IBW) and at weaning (IWW). Litter size was higher in t he intact does, but survival from birth to first week was the same for both groups. The relationship between survival and average birth weight was sli ghtly positive for intact females and null for ULO does. Survival showed a low negative relationship with litter size in intact females, and null for ULO does. IBW was higher in kits of ULO females. IWW was also higher in kit s of ULO females, but this difference disappeared when corrected for litter size. The correlation between the number born alive and the standard devia tion within litter of individual birth weight was null for both groups. The heritabilites of IBW were 0.21 and 0.26 in kits of ULO and intact does, an d 0.25 and 0.24 for IWW in kits of ULO and intact does. Genetic correlation between I]BW in kits of ULO and intact females was 0.98, and 0.90 for IWW. It does not seem that birth weight is now a main factor responsible of the variation in postnatal survival, but if selection for litter size at birth leads to lower survivals, birth weight can be included as an objective of selection. (C) 1999 Elsevier Science B.V. All rights reserved.