Polymorphism in Exon 7 of β- Lactoglobulin (β-LG) Gene and Its Association with Milk Yield in Saanen Goats

Abstract

?-Lactoglobulin (?-LG) is one of milk protein and has important function on technological properties of milk such as cheese making. The relations between whey protein genes and milk yield/ composition have been investigated in previous researches. ?-LG can be utilized as a candidate gene for selection and breeding programs to increase milk yield and protein quality. The aim of this study is to investigate the ?-LG gene polymorphism and relation between ?- LG genotypes and milk yield. In this study, a total of 74 purebred Saanen goats originated from Australia were used to detect polymorphism with PCR-RFLP method. SacII digestion in 427 bp of ?-LG exon 7 (GenBank: Z33881.1) was revealed. Two alleles (S1, S2) and 3 genotypes (S1S1, S1S2, S2S2) were determined in ?-LG/ SacII locus. The ?-LG/S1S1 genotype with only one restriction site revealed two bands (347 bp and 80 bp). The ?-LG/S1S2 heterozygote genotype generated three bands (427 bp, 347 bp and 80 bp). An undigested product, 427 bp was ?-LG/S2S2 genotype which was due to a single nucleotide substitution at position g.4601G>A. S1S2 with genotype frequency (43.3%) higher than the other genotypes. S1 allele frequency was determined predominantly. Deviation from Hardy-Weinberg equilibrium was not identified in the Saanen breed. In ?-LG/ SacII locus, a significant relationship was not found between genotypes and lactation milk yield. However, ?-LG/ S1S1 genotype was observed to have higher lactation milk yield. It is concluded that ?-LG gene could be used as a molecular marker for economic traits such as milk yield and composition.