Abstract

Genetic evaluation of dairy cattle in New Zealand is based on a system originally developed in the 1960s. Major developments in database capability and statistical techniques have taken place over the intervening years. From the mix-1980s a major redevelopment of the information and processing system for cows took place. In 1991, a major review of the sire evaluation system was initiated. A Best Linear Unbiased Prediction (BLUP) procedure has been developed based on an animal model. Implementation of a prototype system is being investigated. In contrast to the existing technique, the prototype involves a concurrent evaluation of cows and sires in all breeds using a repeatability model. This model provides breeding values for every animal (cows with one or more performance records and ancestral animals). The Livestock Improvement database has information on some 10 million animals over more than 50 years. Use of the prototype described in this paper will become routine for ranking of dairy sires from 1994 and will increase rate of genetic gain in the dairy industry by improved accuracy of evaluation and reduced bias. The improved accuracy will result from use of all known genetic relationships among animals. The current system: does not adjust the evaluation of a sire for the merit of its mates dam; ignores sons' evaluations in the evaluation of parents; ignores daughters information in the evaluation of dams. Reduced bias will result from concurrent evaluation across breeds. The current system compares animals to within-breed bases. The assumed model is identical for sires and cows in the prototype system. Furthermore, partitioning of a breeding index (BI) into its components based on information from parents, individuals and progeny is simpler than the current system which uses a recursive method for updating evaluations. Additionally, partitioning of a BI into components will provide useful diagnostic information (particularly for progeny test bulls). Interpretations of PI (production index) and BI information on reports for farmers and AB companies will be similar to the current system.

KD, Johnson

Proceedings of the New Zealand Society of Animal Production, Volume 53, , 43-46, 1993