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

Abstract

Lactose synthase catalyses the formation of lactose which is the major osmole of bovine milk and regulates the milk volume. Alpha-lactalbumin (α-LA) is involved in the synthesis of lactose synthase in the mammary gland. Therefore α-LA is regarded as a plausible candidate gene for the milk yield trait. To determine whether α-LA is associated with milk performance traits, 1,028 Chinese Holstein cows were used to detect polymorphisms in the α-LA by means of single-strand conformation polymorphism (SSCP). Two nucleotide transitions were identified in the 5' flanking region and intron 3 of α-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). RH mapping placed α-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.