Improving accuracy of selection of young bulls by pastoralists

Abstract

A key to maximising response to selection in pastoral cattle kept by groups such as the Sub-Saharan Maasai is an accurate selection of young bulls. A breeding objective was developed based on weight, reproductive rate (days to calving), temperament, tick resistance and trypanotolerance. Accuracy of selection was defined as the correlation between the breeding objective and various selection indices. Accuracy was evaluated assuming availability of information on a range of traits (those in objective plus scrotal circumference) from individuals, parents, grand-parents, half-sibs, progeny and genetic markers. Various scenarios that represent what could occur at the village level were tested. Just selecting on weight alone had an accuracy of 0.538. Additional measurements on the individual (including repeated measures) had a large effect on accuracy. Records on relatives were less helpful than expected. Genetic markers for traits which are difficult to measure (days to calving and trypanotolerance) were helpful for improving accuracy. However, they are unlikely to be used in the near future because of cost and availability. An additional output from this study is simple selection indices that could be implemented immediately at the village level.