Protein is synthesized by genes. Genes are made up of bases Guanine, Cytosine, Thymine and Adenine. These basis code for a amino acid when amino acids are joined together they from protein.
The casein is a protein with calcium. If gene code is disturbed then the protein is wrongly formed. Beta casein A1 has the mutated gene. Mutation means that A.T.C.G. sequence is changed. Thus A1 protein has histidine whereas in A2 there is proline in place of histidine. This is shown in figure below.
When milk is consumed by human beings during digestion A1 Beta Casein forms the casomorphin. This casomorphin is responsible for diabetes, brain disease, development of children and sudden death in children. When A1 casein is digested than intestine secrets DPP4 which causes problems. This is not the case in A2 Beta Casein.
The gene of Holstein is mutated in 90% of Holstein cows and 60% Jersey cow. Among the European cow Gunenshire cow gene is not misstated it is A2 type. So, to say all European breed A1 Casein gene is false.
Now, A2 Casein gene Holstein and jersey cow are selected (because 90% in Holstein is A1 rest 10% are A2). So, we can select A2 Holstein and breed them. Infect A2 Holstein semen is available with ABS India a American supplier. The same in the case with Jersey, only 60% jersey are A1 rest 40% are A2 type. So, we can breed the A2 Jersey cow. Testing of the cow A1 or A2 is done from blood or milk and it is complicated. I know in Roorkee IIT this is being done. May be elsewhere the testing is being done. Unless these finding are not with us we cannot reject or accept a cow. Thus a proper screening is needed.
Our desi cow, goat, buffalo, sheep and camel has A2 gene. Out of the European breeds of cows the Guernsey cows milk is A2 type (Shown below). By the way of our total milk, 50% comes from buffalo, 25 % comes from desi cow and goat and only 25% from exotic cross. So, the possibility of A1 Beta Casein milk supply is less than 20%.
The breeding program of A2 cow is on. The A2 bull semen of Holstein Jersey bull is available farmer is cautions. Upgrading of desi cow like Shahiwal and Gri is also taken up. In super markets A2 milk is sold. There are problems it is good to be alarmed. But we should not be over alarmed because it is economic issue all over world and steps are taken for eradication A1 casein milk. We may find out from National Dairy Research Institute Karnal India the further details.