ABSTRACT Objective genetic improvement in specialized meat breeds of sheep in Britain is based largely on the performance recording and genetic evaluation service provided by Signet and the Meat and Livestock Commission. This includes the use of ultrasonic scanning and a selection index to identify animals with high genetic merit for lean growth. More than 20 sire referencing schemes (SRS) have been established in Britain during the last 12 yr. About half of the performance-recorded flocks in Britain now belong to SRS. Sire referencing schemes create genetic links between flocks and years through the shared use of elite rams (reference sires), often via AI. Multitrait animal model BLUP is then used to provide across-flock genetic evaluations. These in turn allow increased selection intensities and increased response to selection. High responses to index selection for lean growth (about 1.75% per annum in the specialized meat breeds) and other measures of performance are being achieved.
Implications
Sire referencing schemes are cooperative breeding schemes that create genetic links among participating flocks (or herds). These links are usually created through the use of artificial insemination from elite sires. In theory, sire referencing schemes permit across-flock genetic evaluation, increased selection intensity and, ultimately, increased rates of genetic gain. These schemes have had an important role in genetic improvement of several specialized meat breeds of sheep in Britain. Rates of improvement in lean growth being achieved in these industry schemes are close to the rates of gain achieved in experimental flocks. Selection for lean growth in seedstock flocks improves physical and economic performance of progeny in commercial flocks.
Key Words: Carcass Composition, Genetic Improvement, Sheep
© 2001, by the American Society of Animal Science. All rights reserved.
J. Anim. Sci. 2001. 79:E255-E259
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