Genetic variations of α-casein and K-casein genes associated with milk composition in goats

Abstract

The quality of animal milk varies between individuals of the same breed. The present study aimed to detect the favorable SNPs for α-casein (CSN1S1) and k-casein (CSN3) genes associated with high-quality milk traits. Blood and milk samples of Zaraibi and Damascus goats were collected from Sakha farm in Kafr El-Shiekh. The solid non-fat, lactose, protein, and fat contents, were determined in milk using the biochemical method, and amino acids were determined using HPLC. To identify genotypes and nucleotide variations (SNPs), single-strand conformation polymorphism (SSCP) and sequencing methods were used. One-way ANOVA test was used to determine the effect of different genotypes on milk traits. The SSCP-PCR results in Zaraibi and Damascus goats showed that the CSN1S1 gene has 3 genotypes (AA, AB, and BB), and also the CSN3 gene has 3 genotypes (AA, AG, and GG). The results of sequencing showed three SNPs at positions 41G˂T, 69A˂G, and 80C˂T in the CSN1S1 gene, and three SNPs at positions 49C˂T, 111A˂G, and 340C˂T in the CSN3 gene. The milk results showed that the high protein, fat, and lactose content were associated with the AB genotype in the CSN1S1 gene while they were associated with the AG genotype in the CSN3 gene. Likewise, essential and branched-chain amino acids were increased in goat milk with the AB and AG genotypes of CSN1S1 and CSN3 genes, respectively. The essential amino acids for protein synthase were higher in Zaraibi than in Damascus goats. Therefore, the Zaraibi goats may more possess genotypes in the CSN1S1 and CSN3 genes, which affect the fat and protein level in milk.