Vitamin B(12) and transcobalamin in bovine milk: Genetic variation and genome-wide association with loci along the genome

In human nutrition, bovine milk is an essential source of bioavailable vitamin B(12) and B(12)-binding proteins, including transcobalamin. In this study, we estimated genetic parameters for milk content of vitamin B(12) and transcobalamin using milk samples from 341 and 663 Danish Holstein cows, respectively. Additionally, we conducted whole-genome association analysis to identify SNP and genes associated with vitamin B(12) and transcobalamin. Our results indicated moderate to high heritability for vitamin B(12) (0.37 ± 0.18) and transcobalamin (0.61 ± 0.13) content in the Danish Holstein. With a significance threshold of –log(10)P-value > 5.87, significant associations were detected between SNP in Bos taurus autosome (BTA)17 and the log-transformed transcobalamin content of milk; no significant association was detected for vitamin B(12). The significant region in BTA17 was imputed to full sequence for further fine mapping, and the SNP with the most significant associations to transcobalamin were assigned to the transcobalamin 2 (TCN2) gene.