One of the main advantages of genomic (DNA) testing is that it can help identify animals which are carriers of major genes that are responsible for both desirable and detrimental traits, including polledness, dwarfism, etc.

In the suckler sector, a lot of attention is now directed towards another major gene, known as myostatin, which is a key player in regulating muscle growth. Farmers who get their herd genotyped will receive a report showing the myostatin profile across their breeding animals.

What is myostatin?

Myostatin is a gene that controls muscle development by acting as a “brake pedal” on muscle growth. When mutations occur in the gene, muscle development accelerates, producing double-muscled animals.

This trait is commonly seen in Belgian Blue, Charolais, Beef Shorthorn, Limousin and Aberdeen Angus cattle.

There are nine known variants of the gene, with four predominantly found in the UK: E226X, F94L, Q204X and nt821.

Variants

Of these, F94L is known as the “profit gene” as it can increase muscle development without significantly affecting other traits such as calving difficulty or fertility.

Potential drawbacks of the other variants include larger calf birth weights, which can lead to increased calving difficulty. These variants are also linked to reduced milk yield, delayed puberty, smaller pelvic areas and reduced fertility in females.

There are, however, benefits associated with myostatin, including increased kill-out percentages, improved conformation and greater meat tenderness.

Status

When breeding, it is important to know which myostatin genes both females and bulls carry. Every calf receives one copy of the gene from the sire and one from the dam. Where offspring carry two mutated copies of myostatin genes, it often results in double-muscling.

If there is one mutated copy of the gene, it can lead to improved conformation. Where neither copies is mutated, this animal is a non-carrier and will have normal muscling.

Careful matching of bulls to cows can help maximise the benefits of the myostatin gene while reducing associated negative traits.

Pedigree

There is growing awareness of myostatin within breed societies. Pedigree-registered bulls are DNA tested to determine their myostatin status, with this information published in sale catalogues and on pedigree certificates.

Most AI companies are also increasingly displaying myostatin status for their bulls.

If your main goal is easy calving, use non-carrier animals.

However, if you have non-carrier females, you could opt to buy a bull with myostatin mutations, as the offspring should have improved conformation, without the risk of greater calving difficulty.

Where both your cows and bull carry mutations such as nt821, and each passes this on to the calf, there is a higher risk of calving difficulty, but also a high likelihood the calf demonstrates extreme muscling.