Strandberg E, Shook G E
Department of Dairy Science, University of Wisconsin, Madison 53706.
J Dairy Sci. 1989 Aug;72(8):2136-42. doi: 10.3168/jds.S0022-0302(89)79338-3.
Eight breeding programs were evaluated with a simulation study using discounted gene flow. Discounted economic responses and annual genetic changes were calculated. The evaluation was over 25 periods of 13 mo and the population modeled was DHI cows served by AI sires in the US. A breeding program without regard for mastitis gave annual genetic increases of 53.5 kg milk, 2.24 kg fat, .020 cases of mastitis, and an economic response of $98.24. Including SCC or mastitis in selection indexes that maximize economic gain reduced the rate of improvement in yield traits by 1 to 2% but did not reduce clinical mastitis. Instead these indexes slowed the rate of increase in clinical mastitis by 20 to 25% and increased response in economic merit by less than 1%. Restricted selection, which permitted no genetic change in mastitis, reduced the rates of improvement by up to 27% for yield and 17% for economic response. Direct selection against mastitis is unrealistic due to lack of field data on clinical mastitis. Indirect selection would be less efficient than predicted here, due in part to incomplete enrollment in SCC testing program. Simultaneous improvement of both yield and mastitis apparently is not economically desirable due to the antagonistic genetic correlation between yield and mastitis and to the relatively greater economic value and higher heritability of yield.
通过一项使用贴现基因流的模拟研究，对八个育种计划进行了评估。计算了贴现经济反应和年度遗传进展。评估为期25个13个月的时间段，所模拟的群体是美国由人工授精公牛配种的DHI奶牛。一个不考虑乳腺炎的育种计划每年的遗传进展为产奶量增加53.5千克、脂肪增加2.24千克、乳腺炎病例减少0.020例，经济反应为98.24美元。在使经济收益最大化的选择指数中纳入体细胞计数（SCC）或乳腺炎，使产量性状的遗传改进率降低了1%至2%，但并未降低临床乳腺炎的发病率。相反，这些指数使临床乳腺炎的发病率增长速度减缓了20%至25%，并使经济价值反应提高了不到1%。限制选择（即不允许乳腺炎有遗传变化）使产量的遗传改进率降低了高达27%，经济反应降低了17%。由于缺乏临床乳腺炎的现场数据，直接针对乳腺炎进行选择是不现实的。间接选择的效率可能会低于此处预测的结果，部分原因是SCC检测计划的参与度不高。由于产量和乳腺炎之间存在拮抗遗传相关性，以及产量具有相对更高的经济价值和遗传力，同时提高产量和乳腺炎水平在经济上显然并不可取。
