Abstract

The importance of crossbreds in commercial beef production has increased. Consequently, genetic improvement in crossbred performance is of concern to producers and breeders. In current beef cattle breeding programs, genetic improvement is carried out mainly by selection within breed. The genetic correlation between purebred and crossbred performance (r^) may be less than one and within-breed selection may not be optimal for crossbred improvement. In current beef production, two alternative breeding goals can be considered, i.e., the improvement of ’general combining ability” across breeds and genetic improvement for specific types of crossbreds. To improve 'general combining ability”, breed and heterosis effects have to be accounted for in evaluation models, and crossbred information can be used. However, methods to properly account for heterosis effects are not available. Also, the breeding goal should be specific to the type of crossbred, and an approach to achieve genetic progress in specific types of crossbreds is discussed. By this approach, the value of a purebred animal should be determined by both its purebred and crossbred progeny performance. The breeding scheme has to be designed in such a way that both purebred and crossbred information can be collected and properly weighed in a genetic evaluation model. Rotational and terminal crossing systems are two alternatives assuming that mating within breeds is always needed to maintain purebred populations. An evaluation method was discussed for a terminal crossing scheme to achieve optimal crossbred improvement. For a rotational cross, a proper evaluation method has yet to be established. Application of either crossbreeding scheme may result in decreasing the number of breeds, i.e., less efficient breeds in the production system will gradually disappear. For the short term, decreasing of number of breeds may be economically efficient. For the long term, we may lose valuable genetic resources and the question is how we can balance the short and long term interests.
 

M. Wei, J. W Wilton, B. W Kennedy

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 17. Genetics and breeding of dairy and beef cattle, swine and horses, , 516–519, 1994
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