Identification of Single Nucleotide Polymorphism (SNP) in β-Lactoglobulin Gene and Its Association with Milk Composition in Iranian Indigenous Khalkhali Goats

β-lactoglobulin is one of the important milk proteins in several ruminants like goats, sheep and cattle. This study was performed to investigate the genetic polymorphism of exon 7 and 3’ UTR region of β-lactoglobulin (BLG) gene and its association with milk composition in 120 unrelated individuals of Iranian indigenous Khalkhali goats. Purified polymerase chain reaction (PCR) products (427 bp) were sequenced under standard conditions using Sanger sequencing. Alignment of sequenced fragments against reference sequence leads to identification of one single nucleotide polymorphism (SNP), substitution A (frequency equal to 0.44) to C (frequency equal to 0.56) in the 3’ UTR region of BLG gene. Observed frequencies of AA, AC and CC genotypes were 0.12, 0.64 and 0.24, respectively. The effects of identified genotypes on milk composition were analysed using general linear model. We found that BLG gene genotypes have a significant effect on milk parameters except for lactose percentage (p < 0.05). The milk of goats with AA and AC genotypes had higher protein and fat percentages, respectively, in compaired with other genotypes (p < 0.05). Obtained results revealed that, identified genotypes in the BLG gene of Khalkhali goats is not in Hardy-Weinberg equilibrium.