What’s the difference between the proteins in milk?

In today’s dairy industry, some consumers are beginning to ask what the difference is between A1 milk and A2 milk.

Ozarks Farm and Neighbor looked at the differences and what dairy producers might consider breeding for in the future with dairy expert Reagan Bluel, Dairy Field Specialist with the University of Missouri.

It is important to understand that the difference between A1 and A2 milk has nothing to do with lactose.

“A1 and A2 refers to milk protein,” Bluel said. Milk is made up of 87 percent water, 4.9 percent sugar (lactose), 3 to 5 percent fat and 3 to 5 percent protein. Protein in milk is either whey protein or casein. Of the 3 to 5 percent of protein found in milk, casein makes up 80 percent of this.

“When concentrating on the difference between A1 and A2 milk, beta-casein is the main focus,” Bluel explained. There are four different casein proteins. The beta-casein is a string of 209 amino acids, and one very slight change is what differentiates A1 and A2 milk.

“There is one base pair mutation at space number 67 that is the change between A1 and A2,” Bluel said.

This one mutation results in the production of A2 milk, which studies have shown is more digestible because of the change in the string of amino acids.

While some cows can produce both the A1 and A2 protein, to obtain true A2 milk the cows must be homozygous (having two identical alleles of a particular gene or genes) for A2 A2.

Certain breeds of cows tend to be homozygous for A2 A2 more than others, Bluel explained. Highest to lowest A2 milk rank by breed is Guernsey, Brown Swiss, Ayrshire, Jersey, Milking Shorthorn and Holstein. Moving a dairy herd to produce solely A2 milk requires very deliberate breeding, Bluel said, and while a handful of Missouri dairies are doing just that, they currently represent a fairly small portion of the dairy industry. There is a growing interest in A2 milk with consumers, however, especially in the athletic community. Milk has been proven to aid in quick muscle recovery, and with A2 milk being easier to digest, some athletes as well as other consumers with manageable dairy sensitivities are beginning to incorporate A2 milk into their diets. While this has yet to be a far-reaching trend, “anything we can do in our industry to make our product more desirable is a good idea,” Bluel said.

She went on to explain that it does not cost a dairy producer anything extra to find and utilize a homozygous A2 A2 sire for their breeding program.

“Many A2 A2 sires have other good production attributes,” she said.

Utilizing an A2 A2 sire would likely result in more of the milk herd already having the capability of producing the A2 protein if the producer ever decides to switch over entirely to producing A2 milk to meet consumer demands.

As the dairy industry continues to grow and adapt, it is wise for producers to reach out to each other and their consumers to discuss potential new avenues for their product. A2 milk has the potential to develop into a new and interesting market!


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