Abdel-Azim Gamal, Freeman A E
Department of Animal Science, Iowa State University, Ames 50011, USA.
J Dairy Sci. 2003 Feb;86(2):667-76. doi: 10.3168/jds.S0022-0302(03)73645-5.
The advantage of using the genotype of a quantitative trait locus (QTL) in selection schemes of dairy cattle was quantified using stochastic simulation. Three selection plans were studied. In the first plan, young bulls waited for 3 yr until their sisters completed a lactation and then were evaluated and selected based on an animal model. In a second plan, young bulls waited for 5 yr until their daughters completed a lactation. An intermediate 4-yr waiting plan was also studied. Simulation was for 16 yr with overlapping generations. Population and model parameters were proportional to the U.S. Holstein population. The advantage of using a QTL was quantified as the percentage of superiority of QTL-assisted over QTL-free selection using cumulative genetic response. Percentage of superiority was reported for four selection pathways: active sires, young bulls, bull dams, and first lactation cows. A general trend was observed: low superiority in early years of selection that increased to a plateau in later years and then decreased. The superiority of the QTL information was greatest in the 3-yr waiting plan and least in the 4-yr waiting plan. Superiority at plateau for selection pathways ranged from 16 to 26% for the 3-yr waiting plan, from 3 to 12% for the 4-yr waiting plan, and from 5 to 13% for the 5-yr waiting plan. The contribution to selection response attributed to the QTL and the polygenes was quantified. The rate at which the favorable allele approached fixation and the accuracy of predicting breeding values on the percentage of superiority were studied.
利用随机模拟对在奶牛选择方案中使用数量性状位点（QTL）基因型的优势进行了量化。研究了三种选择计划。在第一个计划中，年轻公牛等待3年，直到其姐妹完成一个泌乳期，然后根据动物模型进行评估和选择。在第二个计划中，年轻公牛等待5年，直到其女儿完成一个泌乳期。还研究了一个中间的4年等待计划。模拟进行了16年，世代重叠。群体和模型参数与美国荷斯坦牛群体成比例。使用QTL的优势被量化为QTL辅助选择相对于无QTL选择使用累积遗传反应的优势百分比。报告了四种选择途径的优势百分比：现役种公牛、年轻公牛、种公牛母亲和头胎泌乳母牛。观察到一个总体趋势：选择早期优势较低，随后几年增加到一个平稳期，然后下降。QTL信息的优势在3年等待计划中最大，在4年等待计划中最小。3年等待计划中选择途径在平稳期的优势范围为16%至26%，4年等待计划为3%至12%，5年等待计划为5%至13%。量化了QTL和多基因对选择反应的贡献。研究了有利等位基因接近固定的速率以及基于优势百分比预测育种值的准确性。
