Study shows salmon heart health can be improved

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Heart health in farmed salmon can be significantly improved by changing production methods, according to new research by a team at Norway’s NMBU Veterinary College.

The NMBU study shows that reduced intensity in the hatchery stage can lead to better heart shape and function in farmed salmon.

Heart disorders and circulatory disorders are often observed in connection with mortality after stressful interventions, and varying degrees of abnormal heart shape are also often reported in farmed salmon.

Led by Professor Ida Beitnes Johansen, a concentrated research effort is now underway to uncover causal relationships and possible measures that can ensure good heart health for the salmon.

Called the Helsmolt project, it is a collaborative effort also involving the Institute of Marine Research and other groups.

The main aim is to find out whether production conditions in the freshwater phase can be the cause of developing morphological abnormalities in the heart.

FHF, the semi government body set up to develop knowledge for the Norwegian seafood sector, said the results showed that intensive smolt production where the fish run at higher temperatures is associated with several deviations in the heart shape.

It explains: “Conversely, a slower production at lower temperatures produced fewer morphological deviations and resulted in the salmon getting hearts that are more similar to the wild salmon heart.

“The results also showed that abnormal heart morphology in intensively produced smolt is associated with accelerated stiffening of the heart’s main chamber (ventricle) and the bulbus muscle, which can be linked to symptoms of disease and reduced heart function later in life.

“There is, therefore, reason to believe that rapid smolt production increases the risk of heart disease in Norwegian farmed salmon and that this contributes to increased mortality in salmon approaching slaughter.”

Professor Ida Beitnes Johansen

In addition to this new knowledge about the causes and consequences of abnormal heart morphology in farmed salmon, the project has developed new standardised methods for assessing heart shape and deviations from normal in salmon.

This includes a nomenclature to name the various abnormalities as well as a qualitative scoring system to grade the heart morphology. These methods can be used in research and by the farming industry and will strengthen the further work to understand heart disease in farmed salmon and take improvement measures.

Head of department at FHF Sven Martin Jørgensen says: “Many breeders have internalised the findings from this project and from other ongoing research, and adjusted down the intensity of smolt production at, for example, lower water temperatures.”

FHF adds that, in further research, it is probably necessary to look at all production conditions in their entirety, to understand how the industry can optimise these with regard to the most important organs of the salmon, where the heart and circulatory system have a central role.

 

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