An evaluation on genetic polymorphism of β-Lg locus using PCR-RFLP in sheep breeds reared in Taif

Abstract

Waleed Saad1 *, Fahad Khashoggi2 and Ghazi Abulkhair2

β-Lactoglobulin (β-Lg) is one of the most important proteins in mammals’ milk. It plays a crucial role in milk quality. The polymorphism of β-LG gene can be used as a marker system. To analyze the genotype distribution of β-LG gene in some sheep breeds reared in Taif region of Saudi Arabia and its influence on milk composition, sixty (60) animals belonging to four sheep breeds named Noami, Sawakni, Harry and Nagdi, were utilized. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) test was performed and genetic polymorphism was detected by the digestion of a 452 bp PCR fragment of exon II of β-LG gene with the endonuclease RSAI. The results revealed that Noami and Sawakni breeds belong to β-LG-A genotype while Harry and Nagdi belong to genotype β-LG-B. Sequence analysis of a 340 bp fragment in the promoter region of β-LG showed polymorphism AMONG the examined breeds. Analysis of milk composition in the different breeds indicated that the total protein content of milk was the highest in Noami breed followed by Sawakni, Nagdi and Harry. Concerning milk total fat and total solids contents, Harry breed was the highest, while no significant difference was evident among different breeds in lactose or non-fat solid contents. These results indicate the feasibility of PCR-RFLP test for differentiating sheep breeds and the existence of a significant relationship between β-LG-A genotype and total milk protein content while no clear association between β-LG genotypes and other milk content was proved.