Genetic Polymorphism of CSN2 Gene and its Association with Milk Yield Traits in Crossbred Anglo-Nubian Dairy Goats

Abstract

CSN2 gene is one of the closely linked genes coding for one of the proteins present in milk: casein. Studies on the CSN2 gene have shown an association with increased milk yield in sheep and protein content in cows. This study aims to check the presence of a single nucleotide polymorphism (SNP) in the CSN2 gene of the crossbred Anglo-Nubian dairy goats pooled from three different farms and evaluate its association with milk yield. 101 crossbreed Anglo-Nubian dairy goats were collected with hair follicles, and available data on the milk yield of these individuals were utilized. Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) was used to identify the presence of SNP in the CSN2 gene. The effect of genotypes on milk yield was evaluated using ANOVA via a two-way factorial (2x4) randomized block design (RCBD). A 360bp amplicon was produced, and digestion with SspI resulted in 240 bp and 120 bp fragments, indicating the presence of a SNP. Two genotypes were recorded in the population: the homozygous AA with 0.81 frequency and the heterozygous AA¹ with 0.19 frequency. The studied population is in Hardy-Weinberg equilibrium (χ²=0.18). Significant difference between the average milk yield of the AA and AA¹ genotypes was found, with the AA genotype yielding a 90-day average milk yield of 0.87±0.048 L while AA¹ only averaged to 0.65±0.03 L. The result shows the association of SNP present in the CSN2 gene on milk yield of crossbred Ango-Nubian dairy goats which suggests breeding of goats with the AA genotype.