Evaluation of beta-casein locus for detection of A1 and A2 alleles frequency using allele specific PCR in native cattle of Kermanshah, Iran

The beta-casein locus with different allelic forms of A1 and A2 has been reported among many breeds of dairy cattle. These allelic forms produce beta-casein variants of A1 and A2. The bioactive peptide of beta-casomorphin-7 is produced from proteolysis of beta-casein A1 variant. Beta-casomorphin-7 has morphine like activity and results in some diseases including type 1 diabetes mellitus, cardiovascular disease, sudden death and madness. The aim of present study was to determine the frequency of beta-casein variants in native cattle of Kermanshah Province. Blood samples were taken from 131 native cattle. DNA was extracted from blood using phenol-chloroform method. A fragment with 854 base pairs including a part of exon 7 and a part of intron 6 was amplified by allele specific-polymerase chain reaction (AS-PCR). The frequency of beta-casein genotypes were in Hardy-Weinberg equilibrium (χ2=1.17, P>0.1). The frequency of A1A1, A1A2, and A2A2 genotypes were 16.8, 42.7, and 40.5%, respectively. The frequency of A1 allele was 38.2 and the frequency of A2 allele was 61.8%. In the present study a relatively high frequency of 38.2% was found for beta-casein A1 allele. Finding this percentage of the beta-casein deleterious allele in the cattle indicates the milk of native cattle from Kermanshah Province might contain a high level of beta-casein A1 variant with subsequent increased level of bioactive peptide of beta-casomorphin-7 and its deleterious effects on health.