Substantial evidence demonstrates that the genetic background of milk production traits changes during lactation. However, most GWAS for milk production traits assume that genetic effects are constant during lactation and therefore might miss those quantitative trait loci (QTL) whose effects change during lactation. The GWAS for genotype by lactation stage interaction are aimed at explicitly detecting the QTL whose effects change during lactation. The purpose of this study was to perform GWAS for genotype by lactation stage interaction for milk yield, lactose yield, lactose content, fat yield, fat content, protein yield, and somatic cell score to detect QTL with changing effects during lactation. For this study, 19,286 test-day records of 1,800 first-parity Dutch Holstein cows were available and cows were genotyped using a 50K SNP panel. A total of 7 genomic regions with effects that change during lactation were detected in the GWAS for genotype by lactation stage interaction. Two regions on Bos taurus autosome (BTA)14 and BTA19 were also significant based on a GWAS that assumed constant genetic effects during lactation. Five regions on BTA4, BTA10, BTA11, BTA16, and BTA23 were only significant in the GWAS for genotype by lactation stage interaction. The biological mechanisms that cause these changes in genetic effects are still unknown, but negative energy balance and effects of pregnancy may play a role. These findings increase our understanding of the genetic background of lactation and may contribute to the development of better management indicators based on milk composition.

中文翻译：

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全基因组关联研究通过泌乳阶段相互作用的奶牛产奶性状的基因型。

大量证据表明，泌乳期间牛奶生产性状的遗传背景发生了变化。但是，大多数GWAS的产奶性状都认为在哺乳期遗传效应是恒定的，因此可能会错过那些在哺乳期影响改变的数量性状位点（QTL）。通过泌乳阶段相互作用进行基因分型的GWAS旨在明确检测QTL，其QTL在哺乳期间会发生变化。这项研究的目的是通过泌乳阶段相互作用对乳汁产量，乳糖产量，乳糖含量，脂肪产量，脂肪含量，蛋白质含量和体细胞评分进行泌乳阶段相互作用来进行基因分型，以检测QTL在哺乳期间的变化影响。对于本研究，可获得1,800头第一胎荷兰荷斯坦奶牛的19,286个试验日记录，并使用50K SNP进行基因分型。通过泌乳阶段相互作用，在GWAS中检测到总共7个基因组区域，这些基因组区域在泌乳期间发生变化。基于GWAS的金牛座常染色体（BTA）14和BTA19上的两个区域也很重要，而GWAS在哺乳期间假定了恒定的遗传效应。通过泌乳期相互作用，BTA4，BTA10，BTA11，BTA16和BTA23上的五个区域仅在GWAS中具有显着的基因型。导致这些遗传效应改变的生物学机制仍然未知，但是负能量平衡和妊娠效应可能起作用。这些发现增加了我们对泌乳遗传背景的理解，并可能有助于开发基于乳成分的更好的管理指标。