Abstract
Alpha-1-antitrypsin (A1AT) as a strong protease inhibitor plays a major role in the protection of tissues against proteolytic destruction by neutrophil elastase. Existence of this protein in the mammary gland may increase the survival of milk proteins such as lactoferrin and lysozyme. The biological role of A1AT in tissues such as the mammary gland and results from previous quantitative trait loci (QTL) studies have provoked an investigation of A1AT as a candidate gene influencing milk production traits. The present study assessed the association of a single nucleotide polymorphism (SNP) at position 5504 of the A1AT gene with 305-day milk yield, milk fat and protein percentage and somatic cell score (SCS) in 408 Iranian Holstein cows. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used for genotyping. The effect of the genotype on the traits of interest was analysed using the general linear models (GLM) procedure of SAS software. The frequencies of alleles A and B were 0.633 and 0.367, respectively, and genotypes showed a significant deviation from Hardy-Weinberg equilibrium, which can be a result of selection for milk production traits. Results of association analysis showed a significant relationship between the SNP in the A1AT gene, and fat and protein percentage. Cows of genotype AB had higher milk fat percentage than those of genotype AA. Cows with genotype AA showed a lower milk protein percentage than those carrying genotype AB. When the association of this polymorphism with fat and protein percentage is considered, the SNP could be implemented as a marker in breeding programmes for these traits.Keywords: A1AT gene; candidate gene; mammary gland; PCR-RFLP
Highlights
IntroductionQuantitative traits in dairy cattle are controlled by a large number of genes and environmental factors
Quantitative traits in dairy cattle are controlled by a large number of genes and environmental factors.Several genes that were selected based on their biological actions or that are located in genome regions containing previously identified quantitative trait loci (QTL) have been regarded as candidate genes affecting milk production traits and somatic cell score (SCS) in dairy cattle
The result of the test for Hardy-Weinberg equilibrium for the polymorphism showed that the genotypes in herds 1, 4 and 5 did not show significant deviation from HardyWeinberg equilibrium proportions (P >0.05), while herds 2, 3 and the overall population were not distributed according to Hardy-Weinberg equilibrium (P
Summary
Quantitative traits in dairy cattle are controlled by a large number of genes and environmental factors. Several genes that were selected based on their biological actions or that are located in genome regions containing previously identified QTLs have been regarded as candidate genes affecting milk production traits and SCS in dairy cattle. Markers or QTLs can be considered for selection of desirable genotypes at an early age in the life of an animal. Marker-assisted selection (MAS) as an efficient tool in animal breeding is believed to increase the annual rate of genetic gain in livestock breeding programmes (Meuwissen & Goddard, 1996; Ruane & Colleau, 1996). The expected genetic gain through MAS is estimated to be 44.7% to 99.6% (Edwards & Page, 1994). For effective use of individual markers or genes in animal breeding programmes, existence of an association between them and traits of interest is inevitable
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
