What is the best way to A2 test my dairy animals?

Sep 5, 2023 | Educational Blog

So, you are interested in knowing the A1/A2 status of your cows but are confused about which test is best. The CentralStar A1/A2 genotype test is validated for use on individual animals and can be performed on blood, tissue, or milk; however, determining which method is best depends on your situation and the age of animals you want to test.

If your purpose of A1/A2 testing is to make breeding decisions for your herd, milk, blood, or tissue are all likely sufficient. However, if you are hoping to use the information for marketing an animal with confirmed A2/A2 status, you would be best served to use blood or tissue testing as they offer the highest accuracy level of the methods available at CentralStar.

When deciding which test type to use, also consider how much labor and expertise you have available to collect samples. Milk samples are the easiest to collect as they can be obtained from lactating animals during routine milking by hand-stripping milk into a sample vial.

Collecting a blood or tissue sample requires additional animal handling by you, however, can be collected at any time of an animal’s life, and offer greater accuracy than milk. Using the tail vein to collect a blood sample for an adult animal is best, while the jugular vein is best for calves. Ear notch collection is the same for any age, however, is most often used with calves, likely at the time of ear-tagging. Ear notch and blood sampling both require proper restraint for the safety of humans and animals. Head locks, squeeze chutes, and gates are all helpful tools when collecting samples from cattle of any size.

Obviously, each sample type, milk, blood, and tissue, has uniqueness that are important to understand. If you want to use blood for A1/A2 testing it must be whole blood, collected in a purple top tube – roughly ½ to ¾ full is sufficient. This test is 99% accurate and samples should only be refrigerated, never frozen, before being shipped on ice in an insulated box.

A tissue sample is an ear notch that is collected by using an ear notcher tool. The ear notch is placed in a plastic vial which should be stored in a refrigerator or freezer and shipped on ice in an insulated box. Like blood, testing performed on tissue is 99% accurate.

Fresh, frozen, or preserved milk can be used for A2 testing and is 94% accurate. When collecting a milk sample, proper cleaning and udder prep procedures should be performed; your pre-milking procedure is sufficient. To start, discard the first few squirts of milk onto the ground, then collect milk directly into sample vial. Seven to 10 squirts of milk in the vial is enough for the A1/A2 test alone, but if you are requesting additional testing on the same sample, fill the vial roughly ½ to ¾ full. If using a vial with preservative, like those used in DHI testing, be sure to invert the sample multiple times, roughly 30 minutes after collection to ensure proper mixing. Milk samples should be stored in a refrigerator or freezer and shipped on ice in an insulated box. For the most accurate results, a cow should be at least 5-7 days post-calving before collecting a milk sample.

Each sample type provides advantages… some offer more accuracy, others more convenience. Ultimately, the best method is the one you can collect easily and safely, that meets your goals.

In addition to the A1/A2 genetic test, CentralStar offers ELISA and/or PCR testing for pregnancy, Johne’s, BVD, BLV, mastitis, and Neospora. For additional information, visit mycentralstar.com. Article by Michelle Kaufmann, Customer Solutions Advisor.