Measures to limit the increase of the myostatin mutation – more commonly known as double muscling – in Beef Shorthorn cattle, have been made by the breed’s society.

As of January 2021, any bulls carrying a double deletion of any myostatin variant, or two single deletions of distinct variants, will be ineligible for registration in the herd book, and entry into show classes or breed society sales.

Bulls carrying a single deletion will continue to be eligible for registration and show and sale, but the myostatin status must be declared. It is the double deletion that causes full expression of the double muscling condition. Animals carrying any single deletion will continue to be admitted and the situation will continue to be monitored.

According to breed development director, Carey Coombs, Dunsyre, the board of directors unanimously approved these new regulations after careful consideration of the integrity of the breed type and the breed’s future role in the beef industry.

Such moves have, however, caused several breeders to hit out at the society for doing a dis-service to not only to it’s breeders by not allowing the market to decide what producers are looking for, but also the breed when some myostatins could actually be beneficial.

To further inform breeders of the occurrence of the mutation within their herds the society is providing free testing for the four possible variants, for all first calved heifers when the calf is registered.