B ALLELE OF Β-LACTOGLOBULIN AS A MARKER OF DAIRY TRAITS IN PAKISTANI GOAT BREEDS

Abstract

Genetic isoforms of β-Lactoglobulin (BLG) gene in dairy animals are reported to affect major milk production traits. Present study was planned to identify BLG genotypes in two local goat breeds, Beetal and Daera Din Panah (DDP), to explore their associations with major milk constituents and daily milk yield. Milk and blood samples were collected from animals reared in government livestock farms and privately managed animal herds during December 2010 to January 2012 and further analyzed in Animal Biotechnology laboratory (ABL), University Institute of Biochemistry and Biotechnology (UIBB), Pir Mehr Ali Shah Arid Agriculture University Rawalpindi (PMAS-AAUR). Animals were genotyped for BLG locus using PCR-RFLP method. Quantification of milk proteins and total milk fat contents were carried out using Bradford method and Gerber method respectively. BLG genotype and allele frequencies were computed and tested for associations with major milk constituents and daily milk yield. The genotype frequencies in Beetal goats were; AA: 0.28, AB: 0.55, BB: 0.18 and in DDP goats were; AA: 0.31, AB: 0.53 and BB: 0.15. There was an abundance of heterozygous AB genotype with significantly high frequency of A allele in both animals (Beetal 0.55 and DDP 0.58). The heterozygous AB and homozygous BB genotyped Beetal goats had higher total milk protein (2.64 ±0.855 and 2.56±0.98%, p=0.03) and casein protein (2.25 ±0.71% and 2.19 ±0.81%, p=0.04) contents compared to homozygous AA genotype. The B allele significantly associated with higher whey protein contents in Beetal goats (OR=4.8, CI=1.06-21.62) and total milk fat contents in DDP goats (OR=1.91, CI=1.04-3.51). Overall we report high frequency of BLG AB genotype and A allele in Beetal and DDP goat breeds. However B allele proved to be a good marker of dairy traits in Beetal and DDP goat breeds due to its significant association with higher whey protein and total milk fat contents.