Myostatin and the Suckler Herd: What farmers need to know
December 3, 2025
CAFRE, Beef and Sheep Adviser, John Hamilton comments, “In recent years talk of myostatin has grown steadily around show and sale rings with many farmers turning to it as a valuable aid in selecting replacement breeding stock.”
Myostatin is a gene that influences the production of proteins which control muscle development. Teagasc Geneticist Dr Cliona Ryan described myostatin as acting like a brake pedal on muscle development. When the gene functions as it should muscle growth is controlled, however when mutations or physical breaks occur in the myostatin gene, muscle growth accelerates producing heavily muscled animals.
Depending on your breeding goals this can either be beneficial or detrimental to your production system. Farmers who are in the business of producing heavily muscled show type cattle may favour animals with various mutations of the myostatin gene as it provides the additional muscling, they require to achieve their breeding goals; these farmers are prepared to accept any associated difficulties that may arise in this production system. However, many commercial producers are not as concerned about muscling instead favouring calving ease and high growth rates, these producers favour animals either with myostatin mutations that do not adversely affect these traits or animals that are free from any gene mutations.
At a recent Business Sustainability Group (BSG) suckler meeting, John Hamilton discussed the common mutations found in various common beef cattle breeds. These are F94L, Q204X and nt821. F94L, commonly referred to as ‘the profit gene’ improves muscling without having a major impact on calving difficulty. Q204X and nt821 lead to improved muscling and associated conformation and killing out percentage however on occasion it can also lead to increased birthweights, calving difficulties and some other issues requiring increased labour input. Animals that are free of any myostatin mutations exhibit the natural traits of their respective breeds without the additional muscling.
Animals can have two copies of a particular myostatin gene mutation. These animals are known as homozygous and are sure to pass a copy of that mutation on to their progeny. Other animals may have a singular copy of a particular gene mutation. These animals are classified as heterozygous and there is a 50 – 50 chance they will pass this mutation onto their progeny. Some heterozygous animals will have a copy of two different gene mutations, so could pass either mutation on to their progeny.
In conclusion a greater understanding of myostatin mutations can greatly enhance management decisions on farm. By applying this knowledge, producers can make more informed choices and tailor breeding strategies to align with the specific goals of their enterprise.
If you require additional information on beef breeding management for your farm, please contact your local CAFRE Adviser.