Genome-wide association study for genotype by lactation stage interaction of milk production traits in dairy cattle

摘要

Substantial evidence demonstrates that the geneticbackground of milk production traits changes duringlactation. However, most GWAS for milk productiontraits assume that genetic effects are constant duringlactation and therefore might miss those quantitativetrait loci (QTL) whose effects change during lactation.The GWAS for genotype by lactation stage interactionare aimed at explicitly detecting the QTL whose effectschange during lactation. The purpose of this studywas to perform GWAS for genotype by lactation stageinteraction for milk yield, lactose yield, lactose content,fat yield, fat content, protein yield, and somatic cellscore to detect QTL with changing effects during lactation.For this study, 19,286 test-day records of 1,800first-parity Dutch Holstein cows were available andcows were genotyped using a 50K SNP panel. A totalof 7 genomic regions with effects that change duringlactation were detected in the GWAS for genotype bylactation stage interaction. Two regions on Bos taurusautosome (BTA)14 and BTA19 were also significantbased on a GWAS that assumed constant genetic effectsduring lactation. Five regions on BTA4, BTA10,BTA11, BTA16, and BTA23 were only significant inthe GWAS for genotype by lactation stage interaction.The biological mechanisms that cause these changes ingenetic effects are still unknown, but negative energybalance and effects of pregnancy may play a role. Thesefindings increase our understanding of the genetic backgroundof lactation and may contribute to the developmentof better management indicators based on milkcomposition.