EVALUATION AND EXPLOITATION OF CROSSBREEDING IN DAIRY-CATTLE

Given appropriate genetic resources, there is a range of approaches that can be taken to exploit crossbreeding in dairy cattle. These all require animal evaluation in a procedure that accommodates the genetic mechanisms causing heterosis and the effect of mate genotype on progeny merit. For each characteristic measured, expression in each crossbred type can be considered as a different trait and a multitrait model fitted for predicting a range of proofs, one for each candidate mate genotype. Implementation of mate selection based on these evaluations can be carried out to yield a sensible "fine structure" of program design (optimally exploiting crossing and selection effects) within a chosen "coarse structure" of program design (such as four-pathway design or multiple ovulation and embryo transfer design). Future developments may yield mate selection strategies that also generate such coarse structure designs, accommodating benefits of assortative mating, appropriate progeny testing, avoidance of inbreeding, attention to genetic connection between breeds, herds, and countries, and other animal breeding issues of importance.