The effect of changing the sex ratio on the efficiency of cattle breeding operations

The direct effect of sex control in providing a higher proportion of male calves for beef production can increase the beef output of a dual-purpose population by up to 5%. The actual increase depends on the rate of cow turnover and on the net superiority of males over females in the population concerned. Control of the sex ratio also permits an increase in the intensity of selection, particularly in the paths dams-sons and dams-daughters. The total effect could be an improvement of the order of 10% in the rate of genetic change in the population. Thirdly, control of the sex ratio increases the possibilities for beef crossing in dairy or dual-purpose cattle populations. This can increase the beef output of the population by up to 4%, depending on the rate of cow turnover and the superiority of the beef strains used. If these opportunities are pursued they are likely to drive the population into specialised strains of dairy and beef cattle.