Snelling W M, Golden B L, Bourdon R M
Department of Animal Sciences, Colorado State University, Fort Collins 80523, USA.
J Anim Sci. 1995 Apr;73(4):993-1001. doi: 10.2527/1995.734993x.
Nonlinear mixed-model procedures for analysis of binary data were used to estimate heritability (h2), predict individual genetic merit, and determine genetic and environmental trends for four measures of stayability of beef females. Traits considered were probabilities of a female having 2 [S(2/1)], 5 [S(5/1)], 8 [S(8/1)] and 11 [S(11/1)] calves, given that she calved once. Colorado State University Beef Improvement Center (BIC) and Beckton Stock Farm (BSF) provided data for the analyses. Heritability was estimated using animal model marginal maximum likelihood (AM MML), sire model marginal maximum likelihood (SM MML), and animal model Method R (AM MR). Individual genetic merit was predicted using single-trait animal models with each h2 estimate. Birth year was treated as fixed in all analyses. Only AM MML yielded h2 estimates for all traits in both herds. The AM MML h2 estimates for S(2/1), S(5/1), S(8/1), and S(11/1) were .09, .11, .07, and .20, respectively, for BSF data and .02, .14, .09, and .07, respectively, for BIC data. Differing h2 estimates did not substantially influence rank of individual predictions. Genetic trends in stayability were positive in both herds, although birth year solutions indicated variable or negative environmental trends. Genetic improvement of stayability may be accelerated by incorporating predictions of genetic merit for stayability in selection criteria. S(5/1) may be the most useful trait for consideration in national cattle evaluations.
采用用于二元数据分析的非线性混合模型程序来估计遗传力（h2）、预测个体遗传价值，并确定肉牛母畜四种留种能力指标的遗传和环境趋势。所考虑的性状是母牛在产犊一次后产下2头[S(2/1)]、5头[S(5/1)]、8头[S(8/1)]和11头[S(11/1)]犊牛的概率。科罗拉多州立大学肉牛改良中心（BIC）和贝克顿种畜场（BSF）提供了分析数据。使用动物模型边际最大似然法（AM MML）、父系模型边际最大似然法（SM MML）和动物模型R法（AM MR）估计遗传力。使用单性状动物模型和每个h2估计值预测个体遗传价值。在所有分析中，出生年份被视为固定因素。只有AM MML得出了两个牛群所有性状的h2估计值。对于BSF数据，S(2/1)、S(5/1)、S(8/1)和S(11/1)的AM MML h2估计值分别为0.09、0.11、0.07和0.20；对于BIC数据，分别为0.02、0.14、0.09和0.07。不同的h2估计值对个体预测排名没有实质性影响。两个牛群的留种能力遗传趋势均为正，尽管出生年份的解表明环境趋势可变或为负。通过在选择标准中纳入留种能力的遗传价值预测，可能会加速留种能力的遗传改良。S(5/1)可能是全国牛评估中最值得考虑的有用性状。
