Methods of increasing short term response to full-sib family recurrent selection in small populations

Accelerated recurrent selection (ARS), in which selection is carried out on the predicted value of the progeny rather than on the observed performance of the parents, has been proposed as a method of increasing response to selection and of reducing cycle time. ARS schemes based on test cross evaluation of full-sib families have been compared by stochastic computer simulation. The difference in genetic and economic time scales is emphasised, with the economic long term (21 years) being only 21 or fewer cycles of selection. ARS schemes are shown frequently to offer improvements over standard recurrent selection methods under these circumstances, since they allow more cycles of selection in a given time frame. Schemes with very low effective population sizes often give the greatest response to selection over the time scales considered here. It is suggested that evaluation of cumulative responses to selection over defined periods of time, either by Monte Carlo simulation or by stochastic theory, is the best method of ranking alternative selection schemes. Evaluating response to selection by deterministic methods, or by attempting to take drift into account by evaluating schemes with identical effective population sizes can be misleading.