The genetic merit of stock in the commercial sector of the beef breeding herds is dependent on the rate of genetic gain in nucleus herds and the length of delay it takes to transfer this genetic gain to commercial herds. This paper states the factors controlling the rate of genetic gain and genetic lag and examines the impact of current and future technologies on these factors. The setting of selection objectives and opportunities for crossbreeding in New Zealand beef breeding herds are also mentioned briefly. The maximum theoretical rate of genetic gain in beef cattle herds is about 3.4sigmaT (genetic standard deviations). Current technologies should allow a rate of gain of about 0.25sigmaT but results from New Zealand beef cattle selection experiments suggest that the actual rate achieved in the industry is unlikely to exceed 0.1sigmaT. It is suggested that many new technologies becoming available will either have little impact on the rate of genetic gain or will be too expensive to apply in New Zealand's extensive beef cattle industry. Opportunities will exist for nucleus breeders who are prepared to cooperate with each other giving them a larger pool of breeding cows. The most likely genetic lag using current practices is about 10 years in the New Zealand beef cattle industry. By generating replacement females from only young parents and by accessing sires of above average genetic merit, it should be possible to reduce genetic lag to about 1 year. It is concluded that the New Zealand beef cattle industry could greatly enhance the rate of genetic gain and reduce the level of genetic lag through the application of existing technology. Furthermore, the establishment and application of sound selection objectives is an immediate priority.
Proceedings of the New Zealand Society of Animal Production, Volume 54, , 337-344, 1994
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