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When farmers are purchasing a new stock bull this spring, or making breeding decisions on potential AI sires to use on the herd, consideration should be given to the role of myostatin genes.
While it won’t be the primary or secondary reason for choosing a herd sire, nonetheless, when taken into consideration along with cow type on farm, it can reduce issues like calving difficulty.
Breed societies and AI companies have made great strides in identifying these genes and making the information available to farmers.
But there is still a relatively low level of knowledge around mysotatins among suckler farmers.
What is myostatin?
The myostatin gene is linked to muscling in cattle and prone to mutation from time to time, often through a natural process.
When the myostatin gene does mutate, the more common outcome is animals that exhibit double muscling. But it also affects calving difficulty, both positively and negatively.
There are nine known mutations of the gene, some of which affect all breeds and some versions where the effects are breed specific.
Heritability
Each animal can be a non-carrier (ie no mutation), heterozygous where it carries one version of the mutated gene variant, or homozygous where it carries two versions of the mutated gene variant.
When two homozygous parents are mated, the calf will also be homozygous and exhibit double muscling.
If a homozygous parent is mated with a heterozygous animal, there is a 50:50 chance of the animal having double muscling.
This reduces to a 25% chance when two heterozygous parents are mated and to zero when two non-carriers are mated or a combination of non-carrier crossed to a heterozygous animal.
Downside
While knowing the myostatin status of a herd is an advanatge, the bull is only one part of the jigsaw.
You need to know the status of the cow to make the most informed decision. Without this info, farmers are left to make an assumption of what animals to cross to certain bulls based on myostatin traits.
When it comes to making breeding decisions, the boxes above right outline the more common variants of myostatin genes found in Irish suckler herds along with their associated traits.
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