Direct responses in breeding values to selection of ostriches for liveweight and reproduction

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Abstract
Estimates of genetic parameters and genetic trends for reproductive traits and for liveweight at the commencement of breeding were obtained using data from a pair-mated ostrich flock located at Oudtshoorn in South Africa. Heritability estimates were 0.17–0.18 for egg production, 0.15–0.17 for chick production and 0.35–0.37 for liveweight. Female permanent environmental effects amounted to 0.11–0.17 for egg production, 0.14–0.19 for chick production and 0.30–0.31 for liveweight. Service sire exerted significant effects only on egg production (0.03–0.08) and chick production (0.05–0.10). Genetic correlations of reproductive traits with liveweight were not different from zero. Initial selection in the flock was based on reproduction, in the sense that replacements were descended from the females with the highest uncorrected number of chicks produced during their season of hatch (Chick Production line). Animals that were hatched during the period from 1996 to 2006 were used to establish two more populations. The heaviest birds at ~16 months of age were used as replacements in the line selected for liveweight (Liveweight line). Birds selected for the Control line were of average uncorrected liveweight at ~16 months, and were descended from females that produced an average number of chicks in their season of hatch. Overall, the Liveweight line had higher breeding values than the Control line for the period from 1996 to 2006. The response seemed to be associated with screening from the larger population on breeding values for liveweight, as no cumulative genetic gains were evident since 1996. Breeding values for chick production in the Chick Production line were increased by 3.1% per year from 1990 to 2006. Regressions of individual breeding values in the Control line on the year of hatch indicated no genetic change in either liveweight or chick production. Genetic change in particularly reproduction thus seems feasible in commercial ostriches.

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