The development of transgenic rainbow trout may revolutionise aquaculture. (Photo: University of Rhode Island )

Transgenic rainbow trout may revolutionize aquaculture

UNITED STATES
Friday, March 12, 2010, 15:00 (GMT + 9)

A University of Rhode Island scientist has developed transgenic rainbow trout with enhanced muscle growth, which has yielded fish with what have been described as six-pack abs and muscular shoulders that could revolutionise the commercial aquaculture industry.

Terry Bradley, a professor of fisheries and aquaculture, said that his 10-year research into the inhibition of myostatin, a protein that slows muscle growth, has obtained "stunning results" in the last two years, with trout growing 15 to 20 per cent more muscle mass than standard fish, according to the University of Rhode Island (URI).

"Belgian blue cattle have a natural mutation in myostatin causing a 20 to 25 per cent increase in muscle mass, and mice overexpressing myostatin exhibit a two-fold increase in skeletal muscle mass," said Bradley.

Bradley and his team spent 500 hours injecting 20,000 rainbow trout eggs with DNA types designed to inhibit myostatin. Of the eggs that hatched, 300 carried the gene that led to increased muscle growth. After two years, most fish had the "six-pack ab" effect, even though fish lack standard abdominal muscles. They also have increased musculature throughout.

Studies are under way to determine whether the fish also grow at a faster.

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According to the professor, who also studies salmon, flounder and tuna, the number of muscle fibres in mammals is limited after birth, but in fish, muscle fibre numbers increase throughout their lifespan. Since inhibition of myostatin increases the numbers of muscle fibres, it was not known whether inhibiting myostatin would cause an increase in muscle growth in fish.

"The results have significant implications for commercial aquaculture and provide completely novel information on the mechanisms of fish growth. The results also allow for comparisons between the mechanisms of growth of muscle in mammals versus fish, and it could shed light on muscle wasting diseases in humans," Bradley said.

Some 500,000 metric tonnes of rainbow trout are raised every year in aquaculture facilities across the United States and Europe. In the US, some 1,000 trout farms produce around USD 80 million worth of trout annually.

Assuming Bradley's transgenic fish meet the regulations, it could provide a boost to the industry by enabling farmers to grow larger fish without increasing the amount of feed.

"One of the advantages of this approach is that the modified genes introduced into the fish use the same mechanism and cause the same type of effect that occurs naturally in Belgian blue cattle and other 'double muscled' animals.”

While the trout may look like bodybuilders, Bradley said that they exhibit normal behaviour. He will continue to study the fish in order to learn if the new gene affects other genes, and to determine if new practices will aid in the raising of the trout.

By Michel Loubet
editorial@fis.com
www.fis.com

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