It's not the Jersey milk per se, although Jersey milk is generally higher in butterfat. It's the A2 gene. Cows in other breeds can have the A2 gene as well. Here are a couple of articles on A2: Eating well Wikipedia U of Mn extension I take it that A2 is a recessive gene. So, A2A2 would mean that the cow has both recessive genes. If the cow had only one A2 gene, it would not produce the A2 milk. I don't read that per se, but I suspect that is the case. | 
A2 milk on the farm
