Fertilization of coho salmon eggs with milt from a SRS resistant male. (Photo: AquaGen)

New strong QTL for SRS resistance in salmon coho will contribute to antibiotics use drop

CHILE
Thursday, June 29, 2017, 07:00 (GMT + 9)

A collaboration between researchers in Chile and Norway, directed by the AquaGen company Blue Genomics Chile, has resulted in a breakthrough in breeding for SRS resistance in coho salmon. The discovery of a major QTL for SRS resistance has already been implemented in AquaGen Chile’s egg production. This gives expectations of a significantly reduced infection pressure of SRS in the environment and consequently less need for antibiotic treatment.

The benefits of coho
Chile is today the global leader in coho farming, with a total production of 130 thousand tons annually, representing 18 per cent of the Chilean salmon farming output. Production of coho in Chile has many advantages compared to Atlantic salmon and rainbow trout. Coho have the fastest growth rates, lowest time to harvest and the lowest feed conversion rates. In addition, the very attractive meat color gives the product a significant market in Japan as well as in emerging markets.

SRS is the biggest problem
Coho is immune to Caligus and ISA, but is highly susceptible to the bacterial disease SRS (Salmon Rickettsial Syndrome), also known as piscirickettsiosis. The bacteria are prevalent in all the farmed salmonid species in Chile (Atlantic salmon, rainbow trout, and coho salmon), causing substantial economic losses and animal welfare problems. Treatments with antibiotics may lower losses from outbreaks, but the industry are trying to reduce the use of antibiotics and are considering alternative control strategies. For coho, SRS is responsible for 80 per cent of losses from infectious disease and for most of the need for antibiotic treatments.

Investment in breeding  
AquaGen has during the last three years consolidated coho breeding in Chile by the merger of three previous breeding programs. The joint qualities of these programs together with increased investment in modern breeding technology should result in considerable progress for the coho salmon production in Chile.

          A 500 grams coho salmon (Photo: AquaGen)

A significant QTL discovered
Analyzes of data from several infection tests have shown high inheritance for SRS resistance. A very significant QTL (Quantitative Trait Locus) has been found that explains 46 per cent of the genetic variation in SRS resistance in the coho. Remarkably, close to 60 per cent of fish having two copies of the beneficial variant of the QTL survived a challenge, whereas less than 10 per cent of the fish without the QTL survived.  

Reduction in the use of antibiotics
The 13 million coho eggs produced using QTL-selection in 2017 will have considerably improved resistance to SRS. This way the Chilean industry will help establish selection for improved SRS resistance can support the ongoing efforts to reduce the use of antibiotics in the Chilean salmon industry.

Successful cooperation
This significant discovery for the Chilean salmon industry was possible thanks to the close scientific and technical collaboration between Fundación Chile, ADL Diagnostics, FAVET-Inbiogen Lab. (Veterinary Faculty) at the Universidad de Chile by Dr. Victor Martinez, CIGENE at the Norwegian University of Life Sciences (NMBU), Affymetrics, AquaGen and Blue Genomics Chile.

The research was financial supported by the Chilean funding institutions CORFO (14ITE2-36675/12CTI-16839) and FONDEF-IDEA (ID14I10090), as well as AquaGen and Blue Genomics Chile.

By Editorial
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