Which Cows Produce A2 Milk in the USA?

While standard milk contains a mix of A1 and A2 beta-casein proteins, a 2019 study at the University of Minnesota found that over 50% of its Holstein herd were A2/A2, a trait not actively selected for. In the USA, A2 milk comes from specific breeds and genetically tested herds, not just any cow.

Quick Summary

A2 milk comes from cows genetically tested to produce only the A2 beta-casein protein. While many breeds are used, certain ones like Guernsey, Jersey, and Brown Swiss have naturally higher A2 genetics, but individual testing is essential.

Key Points

• Genetic Testing: A cow's ability to produce A2 milk is determined by genetic testing, not just its breed.

• Naturally High A2 Breeds: Guernsey, Brown Swiss, and Jersey breeds have a naturally higher prevalence of the A2 gene.

• Mixed Herds: Common US dairy breeds like Holstein can produce A2 milk, but a majority may be A1/A2 or A1/A1, requiring testing and segregation.

• US Production: A2 milk is produced in the USA by dedicated farmers who test and segregate their herds to ensure milk purity.

• Breeding for A2: Farmers can selectively breed for the A2 gene by using A2/A2 bulls, a process that can take multiple generations.

What is A2 Milk and Why the Difference?

Milk's protein content is mostly casein, with beta-casein being a significant portion. Beta-casein comes in different variants, but A1 and A2 are the most common. Originally, all domesticated cows produced only the A2 type of beta-casein. A genetic mutation occurred centuries ago in European herds, causing some cows to produce the A1 protein alongside A2. This A1 protein is believed by some to be the cause of digestive discomfort, while A2 is considered easier to digest. The A2 beta-casein is a natural occurrence, not the result of genetic modification. To ensure pure A2 milk, American farmers rely on genetic testing and strict herd management, selecting breeds known for higher A2 prevalence.

A2 Milk-Producing Breeds in the USA

While A2 status is determined by individual genetic testing, some breeds have a higher natural probability of carrying the A2/A2 gene. This makes them preferred candidates for establishing a pure A2 herd. Notable breeds for A2 milk production in the USA include:

• Guernsey: Renowned for their high A2 prevalence, Guernseys often have over 90% A2 genetics. This breed is also known for its rich, golden-colored milk, high in butterfat and beta-carotene. Farms like Eby Manor in Canada and others use them for their high A2 ratio.
• Brown Swiss: This hardy breed from the Swiss Alps is a strong candidate for A2 production, with a breed average of 65-70% A2/A2 status. They are valued for both milk quantity and quality. The Brown Swiss Association actively promotes the A2 trait.
• Jersey: A popular dairy breed, Jersey cows have a higher natural likelihood of producing A2 milk than many common breeds. While general populations might be around two-thirds A2, selective breeding can produce 100% A2/A2 Jersey herds, as seen at Larson Farm. Their milk is known for its high butterfat content.
• Normande and Ayrshire: These breeds are also known for higher A2 percentages. Ayrshire milk is described as having a tremendous balance of component levels and a sweeter taste, making it highly sought after. Some US farms use crossbred cattle with Ayrshire genetics to achieve specific grazing and A2 goals.
• Holstein: The most common dairy cow in the US, Holsteins are typically mixed A1/A2. However, genetic testing shows that over 50% of some Holstein herds can be A2/A2. Farmers can test their herds and separate the A2/A2 cows to produce pure A2 milk, though this requires diligent management.

The Process of Establishing an A2 Herd

Creating a reliable A2 milk supply involves a multi-generational process of genetic selection and strict segregation.

1. Genetic Testing: A simple DNA test, often using a hair follicle sample, is performed on calves and existing herd members to determine their A2 status (A1/A1, A1/A2, or A2/A2).
2. Segregation: A2/A2 cows are physically separated from the rest of the herd to prevent cross-contamination of milk during collection.
3. Breeding: Farmers use A2/A2 bulls for breeding to ensure offspring inherit the desired genetics. An A2/A2 cow bred to an A2/A2 bull will always produce an A2/A2 calf.
4. Verification: Ongoing testing is required to confirm the A2 status of new generations and to maintain the integrity of the A2 herd.

Comparing Milk from Common Dairy Breeds

This table provides a general comparison of common dairy breeds and their A2 potential in the USA. Real-world farm data, especially from genetically tested herds, may vary.

Feature	Holstein	Guernsey	Jersey	Brown Swiss
A2 Prevalence	Mixed; significant portion can be A2/A2 with testing	High; over 90% naturally produce A2	Higher than average; genetic testing needed for pure A2	Higher than average; 65-70% breed average
Milk Volume	High volume producer; dominant in mass dairy production	Moderate volume; lower than Holstein	Lower volume; often prized for richness over quantity	High volume; competitive with Holstein in some areas
Butterfat Content	Average butterfat content; lower than Jersey or Guernsey	High butterfat content; known for richness	Very high butterfat content; contributes to creamy texture	High butterfat content
Best For	Mass production; tested herds for A2 market	Premium A2 milk, cheese, and yogurt	Creamy dairy products, rich A2 milk	Dual-purpose (milk & meat), cheese production

Conclusion

In the USA, A2 milk is not the exclusive domain of any single cow breed but rather the result of careful genetic selection and herd management. While some breeds like Guernseys, Brown Swiss, and Jerseys offer a higher natural probability of producing A2 milk, producers can establish A2 herds from most dairy breeds, including Holsteins, through genetic testing and segregation. Consumers can find certified A2 milk from dedicated US farms by looking for products from companies like a2 Milk® or local producers who have tested their herds. The key takeaway for US dairy farmers is that breeding for A2 genetics is a viable option for tapping into the market for specialized milk products. For more information on breeding for A2, consult resources from organizations like the University of Minnesota Extension.

Frequently Asked Questions

Does the A2/A2 gene affect a cow's health?

There is no evidence to suggest that the A2/A2 gene has any negative or positive effect on the health of the cow itself.

Is all milk from a Guernsey or Jersey cow A2 milk?

No. While these breeds have a higher likelihood of producing A2 milk, only genetic testing of individual cows can confirm their A2/A2 status.

How do farmers test for the A2 protein?

Farmers can test their cattle by sending a hair sample, usually from the tail, to a lab for DNA analysis.

Can Holstein cows produce A2 milk?

Yes, they can. While Holsteins are known for mixed A1/A2 genetics, many individuals are A2/A2 and can produce pure A2 milk if tested and separated from the rest of the herd.

Is A2 milk genetically modified?

No, A2 milk is not the result of genetic modification. It comes from cows that naturally produce only the A2 beta-casein protein.

Does A2 milk taste different than regular milk?

Generally, no. The flavor difference comes from factors like the cow's diet and fat content, not the A1 or A2 protein variant.

How can I be sure the A2 milk I buy is pure?

Consumers should purchase from reputable brands or local farmers who provide transparent information about their genetic testing and segregation practices.