The use of embryo transfer to accelerate genetic improvement in beef cattle.
Previous studies have reported up to double the expected rate of response to selection in breeding schemes based on embryo transfer compared with conventional schemes. However, these studies ignored the variation in family size and reduction in genetic variance in the selected populations. In the present study, using Monte-Carlo simulation for these factors, schemes based on embryo transfer were found to give responses up to 138% greater than conventional schemes using the same number of sires and generating the same number of calves for performance testing. At the same level of inbreeding, and producing the same number of calves for performance testing, the response was 53% greater for an embryo transfer scheme than for a conventional scheme. It is suggested that previous studies may have overestimated the response in an embryo transfer scheme compared with a conventional scheme by up to 50% and underestimated the rate of inbreeding by 150-250%. In addition, the assumption of constant family size may have overestimated the selection response by 0-11% and underestimated the rate of inbreeding by 11-48%.