Molecular screening of bovine β-casein (CSN2) A2 variant in Indonesian Holstein dairy cattle as attempt to produce digestive friendly milk

Cow’s milk-intolerance is a digestive problem on people who not able to digest milk. This problem may relate to the variant of (3-casein (CSN2), especially A1, suggested due to (3-casomorphins (BCM-7) formation during enzymatic digestion, for that selecting cattle free BCM-7 become a concern to produce digestive friendly milk. This study aimed to differentiate A1 and A2 allele variant of CSN2 gene in selected population of Indonesian Holstein cattle. In total 70 cows DNA were collected, and fragment of CSN2 exon 7 which contain Single Nucleotide Polymorphism (SNP) rs43703011 and rs43703013 were amplified. Variant analysis was done by mutation site analysis using PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) with Mspl restriction enzyme and DNA sequence for confirmation. Result shows 2 allele variants of (3-casein that are B type, representing A1 family variant, and A2 in mutation site rs43703013C>G. We found A2 allele in the studied population is superior in frequency than A1 (0.916 vs. 0.084). Of that, 8.6% cattle were heterozygotes that is BA2 and 91.4% were homozygotes A2A2. Cattle which carry A1 allele variant should be excluded from dairy cattle breeding program for further milk production free of BCM-7.