A comparison of "bonus" and "quota" systems utilising the sry gene in beef cattle breeding

Abstract

The SRY gene controls the presence of testes (i.e. maleness) in mammals. This has been demonstrated by Koopman et al (1991), who bred transgenic XX mice with a copy of the SRY gene on an autosome which were phenotypically male, albeit infertile. A fertile XY male with a copy of the SRY gene on an autosome should, theoretically, produce a greater proportion of offspring which are phenotypically male. This would be advantageous in, for example, breeding Terminal beef sires, where male calves are more valuable than females calves on commercial farms. The possible use of beef cattle transgenic for the SRY gene was investigated by Bishop and Woolliams (1991) who found that there were small genetic advantages in breeding schemes using these bulls, compared to traditional breeding schemes, although there may be practical problems in running such schemes. Their findings pertained to a restricted mating strategy (the "quota" system) and a restricted time horizon (15 years), however. This paper investigates the possible application of the SRY gene considering different mating strategies and a flexible time horizon.