ESTIMATES OF GENETIC-PARAMETERS FOR OVULATION RATE, PRENATAL SURVIVAL AND LITTER SIZE IN RABBITS FROM AN ELLIPTIC SELECTION EXPERIMENT

Data from an elliptical selection experiment were used to estimate genetic parameters for components of second parity litter size (LS) in rabbits. The ovulation rate (TOR), the number of implanted embryos and the number of live embryos (TLE) were recorded using laparoscopy at day 12 of gestation and LS was recorded at birth. Prenatal survival (PS) was calculated as LS/TOR. Data from 119 founder does, 120 daughters of 44 does selected on a quadratic index of ovulation rate and prenatal survival and 54 contemporary unselected does were analysed by residual maximum likelihood (REML) in an animal model. Estimates of the proportion of the variance due to the common family environment (c2) were not significantly greater than zero for any trait. Heritabilities of TOR, TLE, LS and PS were estimated to be 0.21+/-0.11, 0.26+/-0.10, 0.29+/-0.12 and 0.23+/-0.10, respectively. Genetic correlations were estimated to be -0.14+/-0.35 between TOR and PS, 0.36+/-0.31 between TOR and LS and 0.87+/-0.08 between PS and LS. Genetic variation in prenatal survival appears to be the major cause of genetic variation in litter size in the rabbit.