Milk from cows carrying the A2 variant of the β-casein protein has attracted increasing interest because it may be easier to digest than conventional milk. As a result, many dairy farms are progressively selecting cows with the A2A2 β-casein genotype. However, little is known about whether genetic variation in genes expressed in the mammary gland could be detected specifically in A1A1 or A2A2 groups. In this study, we compared group of dairy cows carrying A1A1 and A2A2 β-casein genotypes to identify genetic variants in genes active in the mammary gland. We focused on variants that may alter protein structure or potentially influence how genetic information is processed before proteins are produced. These variants were identified using RNA sequencing of milk fat globules (MFG), a milk fraction that contains genetic material from mammary epithelial cells. Under the present RNA-Seq conditions, distinct variants were identified in genes involved in energy production, fat metabolism, RNA processing, and milk secretion. Overall, these findings provide preliminary information potentially relevant for genetic selection strategies targeting the A2A2 β-casein genotype in dairy cattle.

Read the full article in the Journal of Animal Science.