DNA TESTING

Since 2008 it has been a Society requirement that all bulls are DNA tested for sire verification at time of pedigree registration.

A further step is taken now, by adding a requirement to use that sample of DNA to determine the status of the bull for carrying the myostatin gene. This is expressed as a ‘0’ (no copy), a ‘1’ (one copy), or a ‘2’ (two copies). A brief explanation of the implications is given below:

Myostatin – a brief explanation
Basic genetic understanding tells us that genes are inherited – one copy from each parent to make a pair.

Myostatin has been identified as a muscle-growth controller. When it is “switched off”, or “deleted”, muscle can continue to grow unchecked. Hence the loose term “double muscling”. This can be seen in both positive and negative light, depending on your breeding programme.

Results of Igenity’s DNA analysis are written on the certificates as:
0 - Meaning no copy of the deleted myostatin gene
1 - Meaning one copy of the deleted myostatin gene (inherited from one or other parent)
2 - Meaning two copies of the deleted myostatin gene (inherited from both parents)

It follows that the bull will pass on 50% of this part of his genetics to his offspring: so that if your bull has one copy there is a chance that the deletion will be passed on, if he has two copies he will definitely pass on the deletion, and likewise if there is no deletion then the offspring will have at least one copy in his typing.

The interesting bit comes when you add the dam to the equation to make the sum for the progeny’s status!

The implications for an animal having one or two copies of the deletion have been investigated by the Roslin Institute. Their findings were, that the deletion tends to improve muscle conformation, reduce fat, and increase hot weight at slaughter. BUT it also tends to increase birthweight, decrease calving ease, reduce weight gain, reduce internal organ and bone size, and reduce eating quality. These effects are most obvious when the animal is ‘2’ (two copies).

Unfortunately, the whole issue is complicated by the fact that the phenotype (visual appearance) of the animal does not always reflect the genotype (myostatin status). It is also very important to note that natural fleshing is influenced by a great many other things – there are plenty of stock bulls that are ‘0’ which are very nicely fleshed!