Abstract

Visual culling of 16-month old Romney ewe hoggets without access to performance records was carried out by five different groups of farmers who had contributed rams to the Rotomahana Strain Trial. Reasons for culling decisions were recorded and then all ewes, including those 'culled', were retained and farmed as a single flock to compare lifetime performance of culled and selected ewe replacements. Each group of farmers put most of its culling emphasis on size (i.e. smaller sheep were culled), with varying culling emphasis on mouth structure, woolly faces and wool. Less than five percent of the culling emphasis was for foot structure or breed type. All groups of farmers were able to 'select' ewes that had subsequent performance (number of lambs weaning and wool weight produced) superior to their 'culled' group of ewes. There was about a two-fold range among breeders in the effectiveness of their culling in terms of economic returns for lambs weaned plus wool produced over three lambings. Evaluation of ewe production through to seven years of age showed that the effects of visual culling on subsequently ewe performance were maintained over the lifetime of the ewe. The effect of 'culling' using performance traits in the same ewe hoggets as were subjected to visual culling was also assessed. Culling on most performance traits in the same ewe hoggets as were subjected to visual culling was also assessed. Culling on most performance traits was more effective than visual culling, resulting in up to 50% greater economic returns. Post-weaning body weights or fleece weights or a combination of these traits, were the most useful objective culling criteria.

CW, Holmes, and DA Clark

Proceedings of the New Zealand Society of Animal Production, Volume 49, , 175-178, 1989