Polymorphism identification, RH mapping and association of α-lactalbumin gene with milk performance traits in Chinese Holstein

Lactose synthase catalyses the formation of lactose which is the major osmole of bovine milk and regulates the milk volume. Alpha-lactalburnin (alpha-LA) is involved in the synthesis of lactose synthase in the mammary gland. Therefore a-LA is regarded as a plausible candidate gene for the milk yield trait. To determine whether a-LA is associated with milk performance traits, 1,028 Chinese Holstein cows were used to detect polymorphisms in the a-LA by means of single-strand conformation polymorphism (SSCP). Two nucleotide transitions were identified in the 5' flanking region and intron 3 of a-LA. Associations of such polymorphisms with five milk performance traits were analyzed using a general linear model procedure. No significant associations were observed between these polymorphisms and the five milk performance traits (p>0.05). RE mapping placed a-LA on BTA5q21 linked most closely to markers U63110, CC537786 and L10347 (LOD>8.3), which is far distant from the region of the quantitative trait locus (QTL) on bovine chromosome 5 for variation in the milk yield trait. In summary, based on our findings, we eliminated these SNPs from having an effect on milk performance traits.