Abstract
The present study evaluated the effects of increasing the dietary levels of EPA and DHA in Atlantic salmon (Salmo salar) reared in sea cages, in terms of growth performance, welfare, robustness and overall quality. Fish with an average starting weight of 275 g were fed one of four different diets containing 10, 13, 16 and 35 g/kg of EPA and DHA (designated as 1·0, 1·3, 1·6 and 3·5 % EPA and DHA) until they reached approximately 5 kg. The 3·5 % EPA and DHA diet showed a significantly beneficial effect on growth performance and fillet quality compared with all other diets, particularly the 1 % EPA and DHA diet. Fish fed the diet containing 3·5 % EPA and DHA showed 400-600 g higher final weights, improved internal organ health scores and external welfare indicators, better fillet quality in terms of higher visual colour score and lower occurrence of dark spots and higher EPA and DHA content in tissues at the end of the feeding trial. Moreover, fish fed the 3·5 % EPA and DHA diet showed lower mortality during a naturally occurring cardiomyopathy syndrome outbreak, although this did not reach statistical significance. Altogether, our findings emphasise the importance of dietary EPA and DHA to maintain good growth, robustness, welfare and fillet quality of Atlantic salmon reared in sea cages.
Highlights
The aquaculture industry has grown rapidly over the past few decades and has become one of the globally most important food-producing sectors
No significant differences were observed for growth rates, weight or condition factor at earlier sampling times when fish were approximately 600 and 1000 g, highlighting the relevance of long-term trials to reveal all the potential effects of dietary n-3 PUFA on growth performance
The total lipid content in the liver was significantly affected by dietary treatments and was approximately 45 % lower in the fish fed the 3·5 % EPA and DHA diet compared with all other dietary groups, whereas no differences were found in muscle, skin, middle intestine or distal intestine
Summary
The aquaculture industry has grown rapidly over the past few decades and has become one of the globally most important food-producing sectors. The present study aimed to reassess the potential beneficial effects of increased levels of EPA and DHA in salmon diets, focusing on growth, performance, welfare and health, as well as their influence on fillet quality and n-3 PUFA content in different organs and tissues. This feeding trial was conducted over more than 1 year in fish reared in sea cages to mimic the environmental conditions that salmon face in commercial-scale production farms in Norway
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