Varona L, Misztal I, Bertrand J K, Lawlor T J
Department of Animal and Dairy Science, University of Georgia, Athens 30602, USA.
J Dairy Sci. 1998 Apr;81(4):1126-35. doi: 10.3168/jds.S0022-0302(98)75675-9.
Differences in breeding values between dominance and additive models were examined theoretically and with field data. Data included 5.2 million records on stature from 3.0 million US Holsteins. The largest full-sib family had 29 animals, and 7% of all animals had at least one full sib. The dominance model, which accounted for dominance covariances, included the following effects: management, age, stage of lactation, permanent environment, animal additive, and parental dominance (one-quarter of dominance variance) as well as a regression coefficient for inbreeding percentage. Two reduced models were also assumed; in the first, the parental dominance effect was removed, and, in the second, the inbreeding regression coefficient was also removed. The correlations between breeding values in the three models were > 0.999, but breeding values of some animals from full-sib families changed > 5 standard deviations of parental dominance. The largest changes were observed for parents with large numbers of full-sib progeny, with limited information from parents, and without individual performance records. On average, the differences were up to four times larger for cows than for bulls and up to five times larger for dams than for sires. The greatest differences in breeding values between the dominance and the additive models were observed for dams with full-sib progeny, female full sibs, and low reliability bulls with full sibs in the extended family. Animals with large amounts of additive information as progeny-tested bulls were influenced little by the inclusion of dominance. Animals with a large proportion of information coming from animals with dominance relationships, such as cows originating via embryo transfer changed the most.
从理论上并结合实地数据研究了显性模型和加性模型之间育种值的差异。数据包括来自300万头美国荷斯坦奶牛的520万条体高记录。最大的全同胞家系有29头动物，所有动物中有7%至少有一个全同胞。显性模型考虑了显性协方差，包括以下效应：管理、年龄、泌乳阶段、永久环境、动物加性效应、亲本显性效应（占显性方差的四分之一）以及近交系数的回归系数。还假定了两个简化模型；第一个模型去除了亲本显性效应，第二个模型还去除了近交回归系数。三种模型中育种值之间的相关性>0.999，但一些来自全同胞家系的动物的育种值变化超过了亲本显性效应的5个标准差。对于全同胞后代数量多、来自亲本的信息有限且没有个体生产记录的亲本，观察到的变化最大。平均而言，母牛的差异比公牛大4倍，母畜的差异比公畜大5倍。在具有全同胞后代的母畜、雌性全同胞以及大家庭中有全同胞的低可靠性公牛中，观察到显性模型和加性模型之间育种值的差异最大。作为后裔测定公牛且具有大量加性信息的动物受显性效应纳入的影响很小。来自具有显性关系的动物的信息比例很大的动物，如通过胚胎移植产生的母牛，变化最大。
