Abstract

Recent and current developments by Sheep Improvement Ltd (SIL) to provide animal evaluations for a wide variety of flocks using Best Linear Unbiased Prediction (BLUP) methods have encouraged breeders to compare animals bred in different breeding flocks. The data requirements and analytical models needed for BLUP to handle this task are discussed with major emphasis on sire-referencing as a method for achieving adequate genetic linkages among flocks by which animals bred in different flocks may be compared. Despite the high ability of BLUP to accommodate this task and the benefits perceived by many breeders, few specific studies of potential benefits for particular breeding schemes have been reported. In general terms, the impact of across-flock evaluations on annual rates of genetic gain varies for different traits, mating strategies, flock and industry structures. They may not always be cost effective in comparison to within-flock performance selection, especially for larger flocks and when the costs of implementing the flock structures needed to make them accurate and effective in evaluating and disseminating genetic merit are taken into account.

JN, Clarke

Proceedings of the New Zealand Society of Animal Production, Volume 63, Queenstown, 204-208, 2003