Mäntysaari E, Van Vleck L D
Department of Animal Science Cornell University Ithaca, NY 14853.
J Dairy Sci. 1989 Sep;72(9):2375-86. doi: 10.3168/jds.S0022-0302(89)79370-X.
Records of AI-sired cows born between 1978 and 1982 were used to form two composite production and reproduction data sets. First (second) consisted of 35,568 (26,443) first lactations of daughters of 270 (237) sires. Traits were FCM, heifer, and first parity nonreturn rates, days between calving and first insemination, and days open, with means 5075 (5280) kg, .62 (.62), .44 (.49), 81 (81) d and 110 (111) d. (Co)variance components were estimated by REML with an expectation maximization algorithm. Sire model included age, month, herd-year effects, and relationships among sires. Records on animals with observations missing on some traits were included. Estimates of heritabilities, averaged over data sets, were nonreturn rates for heifers and for cows, .02; FCM, .32; days to first insemination, .19; and days open, .10. Genetic correlations between first parity fertility and yield were unfavorable; the highest, .43, was between FCM and days open. Heifer nonreturn rate had a .09 correlation with production and a .26 correlation with cow nonreturn rate. Phenotypic correlations were in the same direction as genetic correlations but were smaller in magnitude. Results suggest that selection only for production would cause deterioration in level of fertility. When economical, AI sires should be evaluated for daughter fertility. A multi-trait model including milk production, days open and relationships among bulls is recommended for genetic evaluation.
利用1978年至1982年间人工授精出生的奶牛记录，形成了两个综合生产和繁殖数据集。第一个（第二个）数据集包含270头（237头）公牛女儿的35568次（26443次）首次产奶记录。性状包括乳脂校正乳（FCM）、小母牛和头胎母牛的不返情率、产犊至首次输精间隔天数以及空怀天数，其均值分别为5075（5280）千克、0.62（0.62）、0.44（0.49）、81（81）天和110（111）天。通过采用期望最大化算法的限制最大似然法（REML）估计（协）方差分量。父本模型包括年龄、月份、牛群年份效应以及公牛之间的亲缘关系。纳入了某些性状观测值缺失的动物记录。数据集平均遗传力估计值为：小母牛和母牛的不返情率为0.02；乳脂校正乳为0.32；首次输精天数为0.19；空怀天数为0.10。头胎繁殖力与产量之间的遗传相关性不利；最高的为0.43，存在于乳脂校正乳和空怀天数之间。小母牛不返情率与产量的相关性为0.09，与母牛不返情率的相关性为0.26。表型相关性与遗传相关性方向相同，但数值较小。结果表明，仅选择生产性状会导致繁殖力水平下降。在经济可行时，应对人工授精公牛的女儿繁殖力进行评估。建议采用包含产奶量、空怀天数和公牛间亲缘关系的多性状模型进行遗传评估。
