Association of polymorphism of the alpha 1-antitrypsin gene with milk production traits in Chinese Holstein

Abstract

Protein degradation in bovine milk affects the quality of dairy products. Alpha 1-antitrypsin (AAT) can protect vulnerable elastic tissues from degradation by neutrophil elastase. The aim of this study was to assess the association of polymorphisms in bovine AAT gene with milk yield and milk composition in Chinese Holstein. Traits analyzed were fat percentage, protein percentage, 305-day milk yield and somatic cell score (SCS). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), created restriction site-polymerase chain reaction (CRS-PCR) and allele specific-polymerase chain reaction (AS-PCR) methods were used to genotype five loci in coding regions of the sequence, including position 5504, 5609, 5624, 5747 and 8178 in Chinese Holstein. The five mutations were all silent mutation that caused no alteration in the amino acid sequence. In order to determine the relationship between the polymorphisms of the AAT gene and milk production traits and SCS, the General Linear Model (GLM) procedure from the Statistical Analysis Software was used. SNP5504 affected milk fat percentage, SNP8178 affected milk protein percentage and SNP5609 and SNP5624 affected 305-day milk yield. These results suggest that AAT is a candidate gene that influences milk production traits and it could be implemented in breeding programmes to improve the production performance of Chinese Holstein cattle.

Keywords: Dairy cattle, α1-protease inhibitor, SNPs, milk traits, somatic cell score