Mating schemes for optimum contribution selection with constrained rates of inbreeding

The effect of non-random mating on genetic response tvas compared for popul ations with discrete generations. Mating followed a selection step where th e average coancestry of selected animals was constrained, while genetic res ponse was maximised. Minimum coancestry (MC), Minimum coancestry with a max imum of one offspring per mating pair (MC1) and Minimum variance of the rel ationships of offspring (MVRO) mating schemes resulted in a delay in inbree ding of about two generations compared with Random, Random factorial and Co mpensatory mating. In these breeding schemes where selection constrains the rate of inbreeding, Delta F, the improved family structure due to non-rand om mating increased genetic response. For schemes with Delta F constrained to 1.0% and 100 selection candidates, genetic response was 22% higher for t he MC1 and MVRO schemes compared with Random mating schemes. For schemes wi th a less stringent constraint on Delta F or more selection candidates, the superiority of the MC1 and MVRO schemes was smaller (5-6%). In general, MC 1 seemed to be the preferred mating method, since it almost always yielded the highest genetic response. MC1 mainly achieved these high genetic respon ses by avoiding extreme relationships among the offspring, i.e. fullsib off spring are avoided, and by making the contributions of ancestors to offspri ng more equal by mating least related animals.