Murphy P A, Everett R W, Van Vleck L D
J Dairy Sci. 1982 Oct;65(10):1999-2005. doi: 10.3168/jds.S0022-0302(82)82450-8.
Multiple regression of genetic evaluations of about 170 Holstein bulls on sire, dam, and maternal grandsire genetic evaluations indicated that the partial regression coefficient for the sire is similar to the theoretical regression coefficient (.45 vs. .50), that the regression coefficient for the dam is much smaller than the theoretical regression coefficient when all records of the dam including her first are included in her evaluation (.12 vs. .35), although about as expected when only first records of the cow and her herdmates are used (.33 vs. .35), and that the regression for the maternal grandsire is larger than expected when his proof and all records of the dam are used in her evaluation (.07 vs. .00), although about as expected when his proof and only her first record is used (-.02 vs. .00). Preferential treatment of potential bull dams is a possible explanation for these results. Genetic correlations among lactations are not likely to be small enough to account for the differences in regression coefficients for the dam's genetic evaluations for all and first lactations. If conditions for selecting bull dams in the future will be similar to what they have been in the past, the conclusion is that genetic evaluations of cows from their first lactation records be used in preference to genetic evaluations from all lactation records for selection of dams of bulls.
对约170头荷斯坦公牛的遗传评估进行多元回归分析，以父系、母系和外祖父系的遗传评估为基础，结果表明，父系的偏回归系数与理论回归系数相近（分别为0.45和0.50）；当母系的所有记录（包括首次记录）都用于其评估时，母系的回归系数远小于理论回归系数（分别为0.12和0.35），不过当仅使用母牛及其同群牛的首次记录时，回归系数与预期大致相同（分别为0.33和0.35）；当外祖父系的证明及其母系的所有记录都用于母系评估时，外祖父系的回归系数大于预期（分别为0.07和0.00），但当仅使用其证明和母系的首次记录时，回归系数与预期大致相同（分别为 -0.02和0.00）。对潜在公牛之母的优待可能是这些结果的一个解释。不同泌乳期之间的遗传相关性不太可能小到足以解释母系所有泌乳期和首次泌乳期遗传评估回归系数的差异。如果未来选择公牛之母的条件与过去相似，那么结论是，在选择公牛之母时，优先使用母牛首次泌乳记录的遗传评估，而不是所有泌乳记录的遗传评估。
