Estimation of Genetic Parameters and Genome-Wide Association Study of Heat Indicators in Holstein Cattle Based on Collar-Mounted Device

The study was to explore population characteristics and influencing factors of heat index and activity peak based on cattle collar data and system and to estimate its genetic parameters, and to identify the genetic markers related to the estrus indicators of cow, the genetic analysis and GWAS were performed for heat index and activity peak, so as to provide useful information for improving dairy cow fertility by formulating breeding strategies from the perspective of genetic breeding.

The heat index and activity peak records of 2 074 milking cows from a large-scale dairy farm in Beijing area were collected from July 2017 to May 2020. The MIXED model in SAS 9.4 was used to analyze the impacts of various factors on heat index and activity peak in Holstein cattle, and the DMUAI module of DMU software was used to estimate the heritability and genetic correlations of heat index and activity peak. The GWAS for heat index and activity peak was performed based on De-regressed Proof (DRP) using FarmCPU software.

In Chinese Holstein cattle, the average heat index was (71.77±19.13) au, and the activity peak was (105.94±30.73) au/2 h. The heritability of heat index and activity peak was 0.04±0.01 and 0.19±0.04, respectively. The genetic correlation between heat index and activity peak was 0.45±0.03. The approximate heat index between the age at first calving in heifer, interval from first to last insemination, and interval from first to last insemination was 0.37, -0.41, and -0.55, respectively. The GWAS for heat index and activity peak identified seven significant single nucleotide polymorphism loci (SNP) at the genome level, and 31 genes nearby the significant SNP (within 300 kb) were found.

The heat index and activity peak obtained by collar system were heritable, and there was a moderate genetic correlation between them. The activity peak was of low heritability and could reflect the heat index of cows to some extent. The activity peak and heat index provided a new direction for studying and breeding the estrus behavior of cows and improving the fecundity of cows. The function of PTGS1 (Prostaglandin-Endoperoxide Synthase1) and NDUFA8 (Ubiquinone Oxidoreductase Subunit A8) genes identified by GWAS was related to the total number of donor embryos, and the function of VEGFA (Vascular Endothelial Growth Factor A) gene was related to the reproduction of cows.