Evaluation of β-casein variants in Egyptian goat, sheep and cattle by allele specific PCR and relevance to β-casomorphin

The beta casein gene (CSNS2) has 12 genetic variants divided into two groups: the first group (A1, B, and G) which differ from the second group (A2, A3 C, D, E, F, H, H2 and I) where A base replaces C base, this leads to potential liberation of a bioactive peptide, β-casomorphin, upon digestion where a histidine replaces a proline at position 67. The allele specific polymerase chain reaction (AS-PCR) was evaluated to distinguish between the beta casomorphin releasing variants (A1 and B) and the non-releasing variants. The sequence analysis was used to determine these variants and confirm it in goat, sheep and cattle. The results showed that cattle carrying allele A1 either homozygous or heterozygous more than sheep and goats. The allele frequency of A1 and A2 is 0.44, 0.56 in goats, 0.43, 0.57 in sheep and 0.54, 0.46 in cattle, respectively. The sequence results reported changing of C base to A base in goat, sheep and cattle. Therefore, this study reported that goat and sheep milk was more safe than cattle milk.