On February 11, 2024, an email was received from a member alerting the board of directors of the discovery of the myostatin NT821 gene deletion in Highland cattle. With information shared from the Highland Cattle Society, American Highland Cattle Association and other associations and breeders, we know that Myostatin is a protein that inhibits muscle cell growth. The “double muscle” gene (of which nt821 is the most well-known) block myostatin and therefore allows muscle cells to grow excessively. NT821 is one variant of over 20 different myostatin variants.
A ‘’carrier’’ denotes that the animal possesses one copy of the Myostatin NT821 mutation associated with the double muscling phenotype. Symptoms may not be physically apparent in carrier animals. ‘’Positive’’ denotes that the animal possesses two copies, with effects being more exaggerated.
What does Myostatin NT821 do?
- Increased muscle mass (in skeletal muscle only – increased number of muscle cells in each muscle – approximately twice as many)
- Reduced intramuscular fat (& slightly reduced subcutaneous & abdominal fat)
- Reduced connective tissue in muscle (related to increased tenderness)
- Slightly decreased bone density (5-9%)
- Slightly reduced internal organ size
- More likely to have calving difficulty (because of slightly narrowed bony pelvic diameter in homozygous females) Homozygous meaning individuals having two identical copies of a particular gene.
Physical differences are more drastic in breeds such as Belgian Blue and Piedmontese, but the gene is present in many other breeds and species as well.
What does Myostatin NT821 do to Highland cattle?
This is currently poorly understood, but how it manifests is known to vary from breed to breed. It appears to have been around for 50+ years and thus far has not raised any eyebrows. There is still much research to be done on the effects of this mutation. Presently, only pictures of ‘’carrier’’ (one copy) animals have been submitted. The animals look to be very nice animals, well-conditioned, not abnormal. We have not yet seen or been informed of animals with two copies of the gene.
As of right now, the Canadian Highland Cattle Society is not taking any position on animals testing as carriers of the mutation NT821. Information gathering is the main goal presently. If you have an animal that tested either as a carrier or positive, please reach out to us. We would like to see pictures if possible and gather general information about the animal’s history.
Testing for Myostatin NT821
To start breeding plans, we encourage our members who wish to test for NT821 to proceed directly with the laboratory Quantum Genetix. The cost of the test is 25$. DNA samples that are already on file and that you submitted (owner of the samples) can be used. If DNA is not on file, you will need to submit your own samples.
Results are reported as:
‘’Carrier’’ denotes that the animal possesses one copy of the Myostatin NT821 mutation associated with the double muscling phenotype. ‘’Positive’’ denotes that the animal possesses two copies .
As a society, we are still inquiring about the legality of authorizing testing on bulls DNA submitted by other entities, such as semen that has been purchased. Currently, we can only tell our members to submit a straw of semen to the lab. As we understand that some straws can be rare and expensive, this is the only legal way for testing at the moment. The lab will be able to best direct you on shipping methods. Otherwise, if the owner of the original sample is still active and can be contacted, they are able to inquire for you if they accept for the test to be done.
It’s important to educate yourself when purchasing Highland cattle and myostatin is another genetic trait that you may want to include in your considerations. It’s always best practice to ask the seller lots of questions and a reputable seller will be transparent and honest with you. If testing for this trait has not been done, it can be requested. As not much is yet known about how widespread the double muscling trait is in Highland cattle, or the effects, breeders will need to use their own judgement when making decisions.