US scientists develop a better rainbow trout

Scientists at the USDA Agricultural Research Service have developed a new rainbow trout line that’s resistant to bacterial coldwater disease (BCWD), a leading killer of farm-raised trout, using cutting-edge genomics.

This is a breakthrough because antibiotics have been the main tool against the disease. By developing fish that are naturally disease-resistant, it’s possible to limit the amount of antibiotics that are used, said Dr Tim Leeds, Research Geneticist at USDA Agricultural Research Service.

It has been difficult to address the disease using traditional breeding methods, but the evolution of genomic technologies has made it easier and, now, cheaper, he said.

The genetic technique they used is called SNP Chip (pronounced “snip chip”). The technique is not a form of genetic modification. There was no such “cutting and pasting” of genes from one species to another, unlike in genetic modification.

Aquabounty’s AquaAdvantage Salmon is an example of an animal that was genetically modified. The goal was to make it grow faster than conventional salmon. To do this, scientists replaced the growth-hormone-regulating gene in Atlantic salmon with the growth hormone-regulating gene from Pacific Chinook salmon.

With genomic technologies, the team were able to identify individual fish that are more resistant to certain diseases, in this case BCWD. From this knowledge, the researchers selected and propagated families that are most resistant to the disease.

Leeds believes that researchers’ better understanding of actual genes and biological mechanisms that affect, for example traits such as disease resistance, will have a large impact on the aquaculture industry.

“When you think about the fecundity (potential to produce offspring) of these fish, it’s worth investing in them to find the truly elite seed stock that can quickly be amplified and really impact the industry,” he said.

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