Using The Hybrids' Information To Optimize Breeding Schemes Of The Male Line In A Three-way Crossbreeding System For Broilers

Using deterministic methods, rates of genetic gain(â–³G)and inbreeding(â–³F )of 18 breeding scheme were compared between pure line selection(PLS)and combined crossbred purebred selection(CCPS) by Monte Carlo, for the sire line of a three-way crossbreeding system, with the same genetic parameters and population size. Meanwhile, the superiority of CCPS to PLS was compared too. The results were as follows:1. The comparison between two different methodsWith the same genetic parameters and population size(9000), genetic gains of crossbred performance using CCPS method, which included purebred and crossbred phenotypic information of the current generation and estimated breeding values for purebred and crossbred performance of parents from the previous generation, were always larger than that of PLS method, which included purebred phenotypic information only in the current generation. For example, with the number of cock(ns)was 60 and the ratio of cock to hen (rsd)was 1:10, genetic gains of the former 6 generation was 1.9846 for CCPS and was higher than that for PLS, which was 0.7172.Inbreeding coefficient was also higher than that for PLS. for example, with ns=60 and rsd=1:10, inbreeding coefficient was 3.71% for CCPS while it was 3.27% for PLS. Results also showed that changing from PLS to CCPS may increase the rates of inbreeding, the larger the nucleus-breeding population was, the lower the rates of inbreeding were when the selection methods were identical.With population size(9000)and ns were identical, The relative efficiency of CCPS to PLS increased first then declined when rsd was raised; With population size and rsd were identical, the relative efficiency of CCPS to PLS also increased first then declined when ns increased. When ns=60 and rsd=1:10, the relative efficiency was the highest and the value was 2.77. We can conclude that CCPS was superior to PLS.2. The comparison within CCPSWith ns was identical, the genetic gains of every generation increased first then declined when rsd was raised. For example, When ns=30, the genetic gains of the former 6 generation was 1.5309 with rsd=1:10, the value was 1.4383 and 1.3896 respectively with rsd=1:20 and rsd=1:5.With rsd was identical, the genetic gains of every generation also increased first then declined with the increaser of ns, the value was the highest when ns=60. for example, when rsd=1:10, the genetic gains of the former 6 generation was 1.9846 with ns=60, the value was 1.5309 and 1.7872 respectively with ns=30 and ns=90.3. The optimization of breeding schemeThe comparison of the 18 breeding schemes showed that the optimum scheme was ns=60, rsd=1:10, the genetic gains of the former 6 generation with CCPS was 1.9846, the inbreeding coefficient was 3.71%.