Castillo-Juarez H, Oltenacu P A, Blake R W, Mcculloch C E, Cienfuegos-Rivas E G
Universidad Autónoma Metropolitana-Xochimilco, México.
J Dairy Sci. 2000 Apr;83(4):807-14. doi: 10.3168/jds.S0022-0302(00)74943-5.
A total of 248,230 primiparous records of Holstein cows calving from 1987 to 1994 (daughters of 588 sires in 3042 herds) was used to evaluate potential genotype by environment interactions among mature equivalent milk yield, lactation mean somatic cell score, and conception rate at first service. Herds were classified into low and high environmental groups using three different criteria: standard deviation of herd mature equivalent milk yield, a combination of herd mature equivalent milk yield mean and standard deviation, and the herd mean of body weight at first calving divided by age at first calving. Genetic parameters were modeled by using multiple-trait linear mixed models and were fitted using the multiple-trait derivative-free software. Heritabilities for mature equivalent milk yield, lactation mean somatic cell score, and conception rate at first service were 0.221, 0.106, and 0.015 in low environment herds and 0.300, 0.093, and 0.009 in high environment herds, respectively. Genetic (and phenotypic) correlations between mature equivalent milk yield and lactation mean somatic cell score, mature equivalent milk yield and conception rate at first service, and lactation mean somatic cell score and conception rate at first service were 0.277, -0.417, and -0.209, (-0.049, -0.180, and -0.040) and 0.173, -0.318, and -0.144, (-0.087, -0.166, and -0.035) in low and high environment herds, respectively. The genetic correlations between pairs of traits were consistently smaller in high environment herds, suggesting that differences in management between the two environment levels lessened the antagonistic genetic association between the traits studied. A long-range plan for low environment herds should focus on improving the level of management, which would greatly reduce the unfavorable correlated changes in lactation mean somatic cell score and conception rate at first service associated with the genetic improvement of mature equivalent milk yield.
共有1987年至1994年产犊的248230头荷斯坦初产母牛记录（来自3042个牛群中588头公牛的女儿）用于评估成熟当量产奶量、泌乳期平均体细胞评分和首次输精受胎率之间潜在的基因型与环境的相互作用。使用三种不同标准将牛群分为低环境组和高环境组：牛群成熟当量产奶量的标准差、牛群成熟当量产奶量均值与标准差的组合，以及首次产犊时的体重均值除以首次产犊年龄。通过多性状线性混合模型对遗传参数进行建模，并使用多性状无导数软件进行拟合。低环境牛群中成熟当量产奶量、泌乳期平均体细胞评分和首次输精受胎率的遗传力分别为0.221、0.106和0.015，高环境牛群中分别为0.300、0.093和0.009。低环境和高环境牛群中，成熟当量产奶量与泌乳期平均体细胞评分、成熟当量产奶量与首次输精受胎率、泌乳期平均体细胞评分与首次输精受胎率之间的遗传（和表型）相关性分别为0.277、-0.417和-0.209，（-0.049、-0.180和-0.040）以及0.173、-0.318和-0.144，（-0.087、-0.166和-0.035）。高环境牛群中各性状对之间的遗传相关性始终较小，这表明两个环境水平之间的管理差异减弱了所研究性状之间的拮抗遗传关联。低环境牛群的长期计划应侧重于提高管理水平，这将大大减少与成熟当量产奶量的遗传改良相关的泌乳期平均体细胞评分和首次输精受胎率的不利相关变化。
