Strategies for dietary antioxidants and pigmentation for farmed salmon under Arctic conditions

Offentlig prosjektsammendrag

The project is an activity under the Arctic Salmon Research Center, which aims to increase the general knowledge about nutrition and feed composition in salmon under Arctic environmental conditions in Finnmark (with varying day length and low sea temperatures) to optimize growth, feed utilization, fish health and product quality. Cermaq has for many years developed feeds with extra amounts of vitamin E and vitamin C. It is known that large fish can deposit more pigment and therefore it is more efficient to give larger fish higher dietary pigment levels. However, this has to be balanced with a final astaxanthin level suitable for harvest – and therefore there is a need to ensure sufficient dietary astaxanthin levels are fed in the event that harvest may be earlier than planned. In addition, there is good documentary evidence that there is a seasonal effect on the pigmentation efficiency – and according to background information this is more prevalent in Northern Norway. Whali et al. (2003) showed that vitamin C helped fish tissues to repair faster. In addition, the lower level of vitamin E in the flesh was associated with gaping and poorer texture. Vitamin E and astaxanthin both have anti-oxidant functions in Atlantic salmon (Bell et al. 2000). The high PUFA content of salmon makes it very susceptible to oxidation: lipid oxidation will not only affect the flavour of the fish (increasing rancidity), but the theory is that this oxidation can also affect the carotenoid content of the fillet. When the pigments react as antioxidants, they lose their colour, so the fish becomes paler, but this is not the only possible mechanism. The aim of the project is to give a recommendation for a dietary pigment (astaxanthin) and antioxidants (Vitamin C and vitamin E) strategy for Atlantic salmon, grown under cold water temperatures under artic conditions, while documenting effects on performance, health, welfare and quality at harvest.