748. an Across-Flock Genetic Analysis of Components of Reproduction in Four South African Merino Resource Flocks

It is well accepted that reproduction is a key profit driver in small stock production systems. The traditional approach for targeting reproductive output in many countries has been through composite trait selection, such as number of lambs weaned per ewe mated (NLW). However, there could be benefit in considering the components of NLW individually. This study reports across-flock analyses of NLW and its components, conception rate, litter size and ewe rearing ability in South African Merino resource flocks. Direct genetic effects were small, but all traits were heritable, estimates ranging between 0.02 for ewe rearing ability to 0.06 for litter size. The only noteworthy unfavourable genetic correlation was between litter size and ewe rearing ability. The traits reported here should be suitable for incorporation into commercial breeding programs of the wider industry.