A1/A2 Milk Research in Indian Cattle

Bovine beta casein A1 and A2 are the most common variants in cattle breeds. Because of the bioactive peptide beta casomorphin-7 (BCM7) produced by raw or processed A1-milk, which has high affinity for opioid receptors and can exert regulatory activities, A1 variant is considered a risk factor for many human diseases, but not by A2-milk, during digestion. The frequency of A1/A2 allele of beta casein is breed dependent and can be very easily checked with simple PCR-RFLP technique. The aim of this article was to review the different studies and assess the status of A1/A2 in Indian native cattle breeds as well as crossbred/taurine populations and breeding bulls being used at different AI centres in India. Analysis of frequency pattern clearly indicated that all Indian native cattle breeds have high frequency of A2 allele and homozygous A2A2 genotype and hence are very good resource for A2 milk. Crossbred, taurine cattle populations and breeding bulls being used at different AI centres have a higher frequency of A2 allele and A1A2 genotype. The percentage of animals with homozygous A2A2 genotype is low. This suggests the need for screening of crossbred/exotic bulls being used in A1 and modify the existing breeding policy so as to drift the herds towards A2.