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Is breeding for A2 milk for you?

A2 milk appears to be all the rage in the dairy industry today. In commercials on TV, online, at the grocery store and even on the farm, many people are talking about A2 milk.  There have been claims in the press that A2 milk is easier for humans to digest, improves health and lowers the risk for some diseases.  Many of these claims have not been proven by science.

What is A2 milk?  

Beta-casein, which makes up 30% of milk protein, exists in two forms: A1 and A2.  A2 milk only contains the A2 variant of beta-casein protein. Cows with the A2A2 gene only produce A2 milk.  Jersey, Guernsey, Normande and Brown Swiss breeds have a higher percentage of A2 genes than Holstein.

Testing your herd

Some farmers have transitioned to A2 herds, but this can take many generations, depending on the status of your herd. One way to determine the status of your herd is to genomic test your cows and heifers.  

If you are already genomic testing, A2 status can be determined for an extra $5 per animal. If you choose to transition to an A2 herd, you can determine which cows and heifers to keep or cull once you receive your genomic results.  

An A2A2 animal bred to another A2A2 animal will always have an A2 offspring. Cows that are A1A2 or A1A1 will not produce A2 milk.

Many A.I. studs have been marketing A2 bulls and more information can be found online or in published bull catalogs.  

Breeding for A2

The University of Minnesota’s research dairy herd at the West Central Research and Outreach Center at Morris uses Holstein, Jersey, Montbéliarde, Normande and Viking Red in their breeding program.  For the Normande breed, six bulls have daughters and the other 14 bulls are genomic only bulls.  As expected, the Holstein breed has the lowest percentage of A2A2 bulls in the Top 25 for Net Merit. The Jersey and Normande breeds have the highest percentage of A2A2 bulls.

Over 50% of the Holsteins in the herd are A2A2, which was not expected because we did not select for this trait.  The 1964 genetic line Holsteins had a lower percentage of animals that were A2A2 at 26%. The crossbred cows and heifers ranged from 36 to 50% of animals that were A2A2.

Table 1 gives the A2 status of the Top 25 Net Merit Proven bulls for Holstein and Jersey and the Top Proven Montbéliarde, Normande and Viking Red bulls available in the U.S.

During the past year, all cows and heifers were genotyped at the University of Minnesota’s research dairy herd in Morris.  The A2 status of the cows and heifers in the herd is shown in table 2.

A2 status of the top genetic bulls by breed

Breed Number of bulls % A2A2 % A1A2 % A1A1
Holstein 25 20 76 4
Jersey 25 72 28 0
Montbéliarde 17 41 47 12
Normande 20 85 15 0
Viking Red 24 54 42 4

A2 status of the University of Minnesota dairy herd in Morris, MN

Breed Number of cows % A2A2 % A1A2 % A1A1
Holstein 114 56 33 11
1964 Holstein 82 26 48 26
Holstein-sired crossbred 65 49 34 17
Jersey-sired crossbred 51 47 45 8
Montbéliarde-sired crossbred 98 36 47 17
Normande-sired crossbred 56 50 45 5
Viking Red-sired crossbred 136 45 40 15

Should you care about A2 milk?

Well, if the industry pays a premium for A2 milk, then you might consider selecting your herd for A2A2 animals and even start using A2A2 bulls.  However, remember that selecting from the top Net Merit bulls is essential to maximize farm profitability, so be sure to check out that list when placing an emphasis on A2 genetics.  

The future will tell if A2 milk is just a fad or if it will permanently have a seat at the table of the dairy industry.

Brad Heins, Extension assistant professor in organic dairy management, and Glenda Pereira, graduate student, College of Food, Agricultural and Natural Resource Sciences

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