A genome‐wide association study reveals a quantitative trait locus for age at first calving in delta/notch‐like EGF repeat containing on chromosome 2 in J apanese B lack cattle

Summary Age at first calving ( AFC ) is an important trait for achieving earlier reproductive performance in cattle. To identify quantitative trait loci for AFC in J apanese B lack cattle, we conducted a genome‐wide association study using 866 animals with extreme AFC values selected from a larger group of 52 009 animals. We identified single nucleotide polymorphisms ( SNP s) on bovine chromosome 2 that were associated with AFC . These SNP s were located within 112.8‐kbp intronic region of delta/notch‐like EGF repeat containing ( DNER ) and proved to be in a state of high linkage disequilibrium. The association was replicated in an independent sample of 2963 animals. In the replicated population, the frequency of the reduced AFC allele ( Q ) was 0.463, and the allele accounts for 8% of the total genetic variance. The effect of allele substitution on AFC was a decrease of 11.54 days. The results suggest that the Q allele could serve as a useful marker in Japanese Black cattle to select animals with superior AFC performance.