Divergent selection for uterine capacity in rabbits.

Abstract

To examine the genetic and phenotypic parameters of uterine capacity and its components in rabbits, we performed a divergent selection experiment for uterine capacity. Rabbit does were unilaterally ovariectomized, and a laparoscopy was performed at midgestation to count the number of corpora lutea and implanted embryos. Selection was performed on litter size in all parities. Genetic parameters were estimated by residual maximum likelihood. For most traits, phenotypic and genetic correlations were in the same range. In unilaterally ovariectomized rabbit does, litter size had a low genetic (.34) and phenotypic (-.08) correlation with ovulation rate, a high genetic (.71) and phenotypic (.60) correlation with the number of implanted embryos, and a high genetic correlation (.89) and moderate phenotypic correlation (.51) with fetal survival. Embryonal survival had a low phenotypic (-.26) or genetic (.12) correlation with fetal survival. A component of uterine capacity, fetal survival in one overcrowded uterine horn, had a low heritability (.05), and consequently limited possibilities for improvement by selection. Uterine capacity, estimated as litter size in one overcrowded uterine horn, had a moderately low heritability (.16). Divergent selection on uterine capacity was effective and a correlated response was found in implanted embryos. No correlated response was found in fetal survival and number of dead fetuses between implantation and birth.