Aquaculture Magazine

Rainbow trout eggs more resistant to flavobacteriosis

AquaGen started its work on flavobacteriosis resistance in 2014.

Norway: The Norwegian selective breeding company, AquaGen, has identified two genetic markers (QTLs) with significant correlation to flavobacteriosis resistance and plans to use them next year for the production of rainbow trout eggs in Norway, the United Kingdom and Chile.
Flavobacteriosis, also known as Rainbow Trout Fry Syndrome (RTFS) is a major problem in rainbow trout production world-wide. It can cause high mortality and wounds in fry and larger fish in freshwater hatcheries and on-growing sites. For their treatment, producers often use antibiotics to protect their farmed fish.
In collaboration with Affymetrix and the US Department of Agriculture (USDA), AquaGen developed a high density SNP-chip capable of genotyping 55,000 SNP markers from one individual fish in one analysis. It is through the use of this SNP-chip that gene markers for infectious pancreatic necrosis (IPN) and flavobacteriosis resistance could be identified.
AquaGen started its work on flavobacteriosis resistance in 2014. A crucial part of this work was the availability of an experimental challenge model developed by a group of scientists at the University of Stirling. A total of 1,500 fry were challenged with Flavobacterium psycrophilum, and subsequently genotyped by the SNP-chip.
A QTL (acronym for quantitative trait locus, 'locus of a quantitative character') search resulted in the discovery of two major QTLs for resistance to flavobacteriosis. Both alone and in combination, the two QTLs have a significant effect in reducing mortality from flavobacteriosis in rainbow trout. The survival among fish with the worst and the best combination of markers was 31 per cent and 84 per cent, respectively.
“The frequency of the beneficial markers is low to moderate in the company’s stock, which means there is huge potential for improving resistance”, says Thomas Moen, Research Director.
Genetic selection to improve flavobacteriosis resistance is relevant to all major markets for AquaGen rainbow trout, and the new product will be available in Norway, the UK and Chile beginning in 2017.
Andrew Reeve, Sales Manager UK/Ireland, believes that this advance represents a major innovation.
"The new product for significantly increased resistance to RTFS will deliver value by reducing the economic impact for the farmer and will improve fish welfare throughout the production cycle", he emphazised.


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