Lin C Y, McAllister A J, Ng-Kwai-Hang K F, Hayes J F
J Dairy Sci. 1986 Mar;69(3):704-12. doi: 10.3168/jds.S0022-0302(86)80459-3.
A total of 920 cows of Holstein-based H line, Ayrshire-based A line, and cross-bred C line between H and A lines was used to determine the genotypic and gene frequencies of milk protein types and to study the relationships of milk protein loci to first lactation yields. Effects of milk protein loci on first lactation performance were examined using classification and gene substitution models. Gene frequencies at the five milk protein loci studied were similar to those reported in the literature. Gene substitution at alpha s1-casein locus showed the greatest effects on first lactation yields compared to those at other milk protein loci. Unfortunately, the favorable B allele at this locus is almost fixed (the frequency of the B allele = .955), a result of long-term selection for high milk production in dairy cattle. The extremely high frequency of a favorable allele at the alpha s1-casein locus imposes a limitation for further genetic improvement at this locus unless a more favorable mutation can be induced. Although favorable alleles at beta-casein, kappa-casein, and beta-lactoglobulin loci exerted smaller effects on first lactation performance than those at the alpha s1-casein locus, their moderate frequencies in the current population can be raised to improve lactation yields through milk protein typing. The combined contribution of the four milk protein loci accounted for 8.9% of phenotypic variance in milk yield, 8.6% in protein yield, ad 5.0% in fat yield.
总共920头奶牛被用于确定乳蛋白类型的基因型和基因频率，并研究乳蛋白基因座与头胎产奶量之间的关系。这些奶牛包括荷斯坦H系、艾尔夏A系以及H系和A系之间的杂交C系。使用分类模型和基因替代模型研究了乳蛋白基因座对首次泌乳性能的影响。所研究的五个乳蛋白基因座的基因频率与文献报道的相似。与其他乳蛋白基因座相比，αs1-酪蛋白基因座的基因替代对首次泌乳产量的影响最大。不幸的是，该基因座上有利的B等位基因几乎固定（B等位基因频率 = 0.955），这是长期对奶牛高产进行选择的结果。αs1-酪蛋白基因座上有利等位基因的极高频率限制了该基因座的进一步遗传改良，除非能诱导出更有利的突变。尽管β-酪蛋白、κ-酪蛋白和β-乳球蛋白基因座上的有利等位基因对首次泌乳性能的影响比αs1-酪蛋白基因座小，但通过乳蛋白分型提高其在当前群体中的中等频率，可提高泌乳产量。四个乳蛋白基因座的综合贡献占产奶量表型变异的8.9%、蛋白产量的8.6%和脂肪产量的5.0%。
