Genetic Improvement of Ewe Reproductive Traits in Rideau-Arcott
The goals of this research were to estimate genetic correlations among parities, estimate genetic parameters among reproductive and growth traits, predict the selection response for the traits, and propose a selection index for ewe productivity. Because of major genetic differences found between reproductive traits in the first and subsequent parities, they were evaluated as two separate traits. Selection for reproductive traits in the first parity were predicted to result in greater correlated response in later parities than direct selection. Selection based on growth traits resulted in higher correlated response than direct selection on total weaning weight, a composite ewe reproductive trait, but it was accompanied by small negative response on litter size at birth. Such negative response was countered using a selection index. In addition, the use of selection index was predicted to improve the correlated response on the target composite reproductive trait over the direct selection. Selection response for ewe reproductive traits could be improved by indirect selection procedures.