Using Genetics to Improve Sheep Muscling

Increased lean meat yield can be achieved by selecting meat sheep sires for known genes that have positive effects on meat traits along with the traditional breeding selection methods.

Researchers have found a naturally occurring change in a gene that is known to increase muscle and decrease fat. The gene is myostatin, a suppressor of skeletal muscle growth, and a change in the gene reduces the production of the myostatin protein, resulting in increased muscling and reduced fat. Variation in myostatin have been identified in both sheep and cattle breeds.

Preliminary research carried out by Australia's Sheep CRC's doctorate student Fay Haynes from the University of New England, Armidale, has found that the number of copies of the altered myostatin gene influences muscling.

Sheep with two copies of the myostatin change have at least a 17-percent increase in carcass size and those animals with one copy have approximately a 9-percent increase, with both decreasing carcass fat by approximately 12 percent.

Research on naturally occurring changes to the gene has been of international interest with studies carried out in the United States, Belgium, France, New Zealand and also Australia, and all have found an increase in skeletal muscle size in animals with a gene change that reduces myostatin protein.

Following Fay's preliminary findings, her early research also recognized that nutrition affects the growth of lambs with only one copy of the altered myostatin gene.

She found that lambs with a copy of the gene that were offered unrestricted access to feed had more muscle growth than those without a copy, but when offered restricted nutrition, the lambs with one copy performed more poorly than their normal counterparts.

Further research is required to determine the effect of this gene on development and other performance traits such as lamb survival, reproduction, growth and efficiency characteristics.

Reprinted in part from SheepCRC, AU

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