Arango J, Misztal I, Tsuruta S, Culbertson M, Herring W
Department of Animal and Dairy Science, University of Georgia, Athens, 30602-2771, USA.
J Anim Sci. 2005 Jun;83(6):1241-6. doi: 10.2527/2005.8361241x.
Records of on-test ADG of Large White gilts were analyzed to estimate variance components of direct and associative genetic effects. Models included the effects of contemporary group (farm-barn-batch), birth litter, pen group, and direct and associative additive genetic effects. The area of each pen was 14 m2. The additive genetic variance was a function of the number of competitors in a group, the additive relationships between the animal performing the record and its pen mates, and the additive relationships between pen mates. To partially account for differences in the number of pen mates, a covariable (qi = 1, 1/n, or 1/n(1/2)) was added to the associative genetic effect. There were 4,946 records from 2,409 litters and 362 pen groups. Pen group size ranged from 12 to 16 gilts. Analyses by REML converged very slowly. A grid search showed that the likelihood function was almost flat when the additive genetic associative effect was fitted. Estimates of direct and associative heritability were 0.15 and 0.03, respectively. Within the BLUPF90 family of programs, the mixed-model equations can be set up directly. For variance component estimation, simple programs (REMLF90 and GIBBSF90) worked without modifications, but more optimized programs did not. Estimates obtained using the three values of qi were similar. With the data structure available for this study and under an environment with relative low competition among animals, accurate estimation of associative genetic effects was not possible. Estimation of competitive effects with large pen size is difficult. The magnitude of competition effects may be larger in commercial populations, where housing is denser and food is limited.
分析了大白猪后备母猪的测定期平均日增重记录，以估计直接遗传效应和关联遗传效应的方差分量。模型包括同期组（农场-猪舍-批次）、出生窝、栏组以及直接和关联加性遗传效应。每个栏的面积为14平方米。加性遗传方差是组内竞争个体数量、记录个体与其栏内同伴之间的加性亲缘关系以及栏内同伴之间加性亲缘关系的函数。为部分考虑栏内同伴数量的差异，在关联遗传效应中加入了一个协变量（qi = 1、1/n或1/n(1/2)）。共有来自2409窝和362个栏组的4946条记录。栏组大小从12头到16头后备母猪不等。通过REML进行的分析收敛非常缓慢。网格搜索表明，拟合加性遗传关联效应时，似然函数几乎是平坦的。直接遗传力和关联遗传力的估计值分别为0.15和0.03。在BLUPF90程序家族中，可以直接建立混合模型方程。对于方差分量估计，简单程序（REMLF90和GIBBSF90）无需修改即可运行，但更优化的程序则不行。使用qi的三个值获得的估计值相似。根据本研究可用的数据结构以及动物间竞争相对较低的环境，无法准确估计关联遗传效应。对于大栏舍规模，竞争效应的估计很困难。在商业群体中，竞争效应的大小可能更大，因为那里的饲养密度更高且食物有限。
