Understanding Myostatin E226X

Recently, a copy of a Myostatin Gene mutation, known as Myostatin E226X, was described within the Shorthorn population in Australia.

The Myostatin Gene is essential for the proper regulation of skeletal muscle mass. Mutations to the Myostatin gene make the gene less active or inactive, resulting in variations to normal phenotypes which can include muscular hypertrophy or double muscling.

Myostatin E226X is one of several known mutations of the Myostatin gene, with different mutations known to occur in several different cattle breeds. Whilst the exact origin in Shorthorns is not known, E226X is largely associated with the Maine Anjou breed.

E226X is an autosomal recessive genetic defect, which means it follows a simple recessive pattern of inheritance. It is known to be a disruptor gene and whilst there is currently little research to describe the exact effect of E226X, similar disruptor genes in homozygous (not heterozygous) affected animals have been known to produce variations from normal phenotypes including increased birthweights and dystocia, reduced fat and marbling, hyperplasia (increase in the number of muscle fibres) and hypertrophy (increase in the size of muscle fibres). Also improved beef yield and improved tenderness.

Not all genetic defects are necessarily bad. Gene mutations can produce results that are categorized as either Favourable (such as the Polled gene), Unfavourable or Lethal defects.

In the case of Myostatin mutated disruptor genes, many consider one form of the gene (heterozygous carriers), to be favourable as they may increase muscularity and yield, without having any significant impact on the other production traits.

Double muscling tends to conjure up certain images from breeds that have selected for homozygous Myostatin mutation carriers. Whilst these breeds may express extreme muscularity, it is known that within at least some of these breeds, genetic selection for these traits has also occurred and contributed to the current phenotypes. In breeds such as Shorthorns, where a more “balanced” genetic selection has occurred, the effects on homozygous E226X carriers may not be as severe. It is important to understand that not all well-muscled Shorthorns will carry any copies of the E226X mutation and that they may in fact be the result of genetic selection only.

There is a very simple DNA test available for members who wish to understand the Myostatin E226X status of their animals. Any breeders who wish to test their animals should send tail hairs, a semen straw or a TSU sample to Shorthorn Beef for DNA testing. There are two different test options available. First is a standalone test which costs $33 or the test can be added to a HD50K bundle for an extra $11.

If you have any questions, please read the below fact sheet or contact the Shorthorn Beef office.

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About Shorthorn

The Shorthorn breed is truly unique, from their distinctive roan colour, to their rich breed history and most importantly, the wonderful community of breeders, there is nothing else quite like a Shorthorn.

The key to the Shorthorn breeds advantage lies in their balanced genetic profile, driven by market participation that has been developed and refined, after more than 200 years of genetic selection under Australian conditions.

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