Westell R A, Van Vleck L D
J Dairy Sci. 1985 May;68(5):1306-10. doi: 10.3168/jds.S0022-0302(85)80962-0.
Estimated transmitting ability for milk production calculated from only first lactation records was regressed on milk proofs of the sire and maternal grandsire and either estimated transmitting ability of the dam calculated from only first lactations or estimated transmitting ability of the dam calculated from all lactations of a data set in which all cows were required to have milk records of first lactation. Records of 222,576 Holstein heifers in the northeastern United States were analyzed. Partial regression coefficients were similar to those from reports in which all records in the data file were used to estimate transmitting abilities. The partial regression coefficient for estimated transmitting ability of the dam from all lactation records (.17) was smaller than the approximate theoretical regression coefficient (.70). The partial regression coefficient for estimated transmitting ability of the dam calculated from first records (.72) was similar to the approximate theoretical regression coefficient (.80).
仅根据头胎泌乳记录计算得出的产奶量估计传递能力，与公牛及其外祖父的乳脂率证明，以及根据头胎泌乳单独计算得出的母牛估计传递能力，或根据要求所有母牛均有头胎泌乳记录的数据集的所有泌乳期计算得出的母牛估计传递能力进行回归分析。对美国东北部222,576头荷斯坦小母牛的记录进行了分析。偏回归系数与使用数据文件中的所有记录来估计传递能力的报告中的系数相似。根据所有泌乳记录得出的母牛估计传递能力的偏回归系数（0.17）小于近似理论回归系数（0.70）。根据头胎记录计算得出的母牛估计传递能力的偏回归系数（0.72）与近似理论回归系数（0.80）相似。
