Correlated response in early embryonic development in rabbits selected for litter size variability

Abstract

[EN] A divergent selection experiment for litter size variability was carried out in rabbits. The litter size variability was estimated as the phenotypic variance of litter size within female. The aim of this study was to assess the effect of selecting for litter size variability on early embryonic development and survival after 7 generations of divergent selection (high and low variability lines). A total of 30 non-lactating multiparous does per line were used. The ovulation rate and early embryonic development were analysed using Bayesian methodology. Ovulation rate was not affected by the selection process. At 28 h of gestation, embryonic development and survival were similar in both lines. At 48 h of gestation, the majority of embryos in the high line were in the early morulae stage. The high line had a higher proportion of early morulae (79.54 vs. 53.43%; P=0.94) and a lower proportion of compacted morulae (20.46 vs. 46.57%; P=0.93%) than the low line. At 72 h of gestation, the high line had 1.59 fewer embryos than the more homogeneous line (P=0.85), due to reduced embryonic survival (0.60 vs. 0.74; P=0.93). The high line continued to show a higher proportion of early morulae (21.01 vs. 3.69%; P=0.93) and a lower proportion of compacted morulae and blastocysts (78.99 vs. 96.31%; P=0.94) than the low line at 72 h of gestation, indicative of reduced embryonic development. In conclusion, selection for homogeneity in litter size had a positive impact on embryonic traits.