Genetic and environmental trends were evaluated for post-weaning body weights of 20677 weaned rabbits of New Zealand White (NZW) and Z-line born between 1982
and 1996 from 1212 sires and 3168 dams. Multi-trait animal model was used for such evaluation taking into account body weights at 8 and 12 weeks of age. Heritability estimates for the two body weights in NZW were higher than those in Z-line; being 0.34 and 0.30 in NZW and 0.10 and 0.25 in Z-line at 8 and 12 weeks of age, respectively. Common litter effects were higher in Z-line (averaged 37.65%) than those in NZW (averaged 29.95%). All correlations between
the two body weights were moderate orhigh; being 0.73 and 0.69 for genetic correlations, 0.60 and 0.64 for phenotypic
correlations, 0.49 and 0.64 for common-litter correlations and 0.45 and 0.68 for environmental correlations in NZW and Zline rabbits, respectively. The ranges in predicted breeding values (PBV) for body weights at 8 and 12 weeks of age were 572 and 639 gram in NZW, while they were 216
and 449 gram in Z-line, respectively; i.e. wide variations in PBV of body weights between the two strains were in favor of Z-line rabbits. The accuracies ( raa$ ) of minimum
and maximum estimates of PBV were mostly higher in NZW than those in Z-line for the two weights; ranging from 0.48 to 0.73 in NZW and 0.38 to 0.62 in Z-line. Genetic trends indicate that PBV were mostly positive in NZW and negative in Z-line over the whole period of the study. In NZW rabbits, the trend indicates that the plateau for the breeding values reached soon at the beginning years, while in Z-line the rates of change in breeding values were very low
during the five years of the study. Plots of year-season trends indicate that environmental effects (i.e. seasonal-annual variations) play a large role in improvement
of the two body weights in both lines. |
