Milk protein polymorphism in taurine (Bos taurus)and zebu (Bos indicus) populations bred in hot climate

The genetic variation at four milk protein loci αs1-casein (CSN1S1), β-casein (CSN2), κ-casein (CSN3) and β-lactoglobulin (LGB) was investigated in 358 animals belonging to seven populations well adapted to hot climatic conditions, reared in Africa and Italy. Bos taurus (Somba, Lagune and Modicana), Bos indicus (Sudanese Zebu Peul, Azaouak and Adamawa), and B. taurus x B. indicus (Borgou) were studied by adapting different molecular methodologies to evaluate their genetic variability. All loci were polymorphic and a new CSN2 synonymous variant, named A2′, was detected and characterized. Noteworthy differences in the distribution of alleles and haplotypes were observed between zebuine and taurine cattle showing that milk protein polymorphism is suited for discriminating B. taurus from B. indicus efficiently, and also taurine breeds. Milk protein loci, being positively selected loci, can also provide information about the occurrence of germplasm particularly useful for breeding strategies and production improvement.