Testing for undesirable traits in cattle: an Australian perspective.

A variety of autosomal recessive defects, many lethal to the newborn calf, have been recognized in Australia. Definition of a defect at the biochemical or molecular level facilitates development of heterozygote detection tests essential for efficient disease control programs. The prevalence of alpha-mannosidosis in Angus and Murray Greys, generalized glycogenosis in Brahmans and Shorthorns, and citrullinemia in Holstein/Friesians has been reduced as a result of industry-sponsored disease-control programs. These defects were disseminated as a consequence of selection focused on desirable traits carried by individuals. In the long term, an increase in crossbreeding in commercial beef production will reduce the significance of recessive defects. Caution will be required to reduce the risk of dissemination of recessive defects resulting from increased selection pressure within the dairy industry presently dominated by Holstein/Friesians.