The genetics of dairy cattle are evolving quickly, with increasing interest in traits that align with market demand and consumer perception. One trait drawing attention is the type of beta-casein protein found in milk—specifically, the A2 variant.
What Is A2 Milk?
Beta-casein makes up about 30% of milk protein and exists in two primary forms: A1 and A2. Cows can have one of three genetic combinations:
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A1A1 – Produces only A1 beta-casein
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A1A2 – Produces a mix of both A1 and A2 proteins
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A2A2 – Produces only A2 beta-casein
Milk from A2A2 cows is marketed as A2 milk, which some claim is easier to digest and less likely to cause discomfort compared to regular milk. While these claims are popular in consumer circles, scientific evidence remains inconclusive. A2 milk still contains lactose, so it is not a lactose-free alternative.
Breeding for A2A2: Is It Worth It?
If the marketplace begins offering premiums for A2 milk, investing in A2A2 genetics may be beneficial. Genomic testing is an efficient way to identify the A2 status of cows and heifers, costing about $5 per animal. Once the A2A2 animals are identified, producers can breed selectively to gradually transition the herd.
The University of Minnesota’s research herd, which includes breeds such as Holstein, Jersey, Normande, and Viking Red, has provided valuable insight into the current status of A2 genetics. Among their Holsteins, 56% were A2A2, while crossbred animals showed a range of 36% to 50% A2A2 prevalence, suggesting that the trait is already well-distributed—even when not specifically selected for.
A study involving around 3,000 cows suggested potential differences in production and longevity between A2A2 and A1A1 cows, but not between A2A2 and A1A2 cows. However, researchers noted potential bias due to culling criteria based on beta-casein status. More data is needed to confirm if A2 genetics offer additional benefits beyond potential digestibility.
Market Trends: A2 Dominance in AI Bulls
As of today, most bulls in U.S. artificial insemination (AI) programs are A2A2. A recent survey of major AI companies found over 800 Holstein bulls marketed as A2A2, indicating a major genetic shift. Holsteins, once primarily A1A1 or A1A2, are moving steadily toward A2A2 status through breeding decisions made by AI companies.
This shift suggests that producers may already be incorporating A2 genetics by default when selecting bulls based on Net Merit or other performance traits, reducing the urgency to make A2 status a standalone selection priority—unless a premium market emerges.
Other Single-Gene Traits on the Radar
While A2 receives attention, other single-gene traits are also gaining ground. One such trait is polledness—naturally hornless cattle—which is increasingly relevant as animal welfare standards tighten. Unlike A2, which is a recessive trait, polled is dominant, meaning genetic progress toward polled herds can be faster if actively selected.
Other emerging traits of interest include:
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Kappa-casein – Linked to cheese yield
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Slick gene – Promotes heat tolerance through shorter hair
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Methane efficiency and feed efficiency – Key for environmental and economic sustainability
Balanced Selection for Long-Term Profitability
Selecting for A2 may align your herd with future market trends, especially if consumers continue to seek alternatives perceived as easier to digest. However, the most profitable approach remains a balanced selection strategy that includes high Net Merit bulls, while also factoring in market-relevant single-gene traits.
As genetic tools and market demands evolve, dairy producers have more options than ever to shape their herds for both performance and consumer appeal—whether that’s through A2 milk, polled calves, or feed-efficient cows. The key is staying informed and strategic in trait selection.
