Hacker News Reader

Looks like good old fashioned genetic screening.

> A genetic test, developed by the a2 Milk Company, determines whether a cow produces A2 or A1 type protein in its milk. The test allows the company to certify milk producers as producing milk that does not metabolise to β-casomorphin 7.

https://en.wikipedia.org/wiki/A2_milk

Jersey, Guernsey cows produce milk that only has the A2 protein naturally. No screening required. http://www.honeymoonbrands.com/milk and https://www.motherjones.com/environment/2014/03/a1-milk-a2-m...

Your first link doesn't mention A1/A2 at all, and the second says "The A1 protein is much less prevalent in milk from Jersey, Guernsey, and most Asian and African cow breeds, where, instead, the A2 protein predominates." which doesn't support your claim that they only produce A2.

They make a genetic test, the gene variation is from a natural mutation.

They use the test to certify herds as producing the A2 milk.