Endogenous production ofn-3 long-chain PUFA from first feeding and the influence of dietary linoleic acid and theα-linolenic:linoleic ratio in Atlantic salmon (Salmo salar)

Abstract

AbstractAtlantic salmon (Salmo salar) possess enzymes required for the endogenous biosynthesis ofn-3 long-chain PUFA (LC-PUFA), EPA and DHA, fromα-linolenic acid (ALA). Linoleic acid (LA) competes with ALA for LC-PUFA biosynthesis enzymes leading to the production ofn-6 LC-PUFA, including arachidonic acid (ARA). We aimed to quantify the endogenous production of EPA and DHA from ALA in salmon fed from first feeding on diets that contain no EPA and DHA and to determine the influence of dietary LA and ALA:LA ratio on LC-PUFA production. Salmon were fed from first feeding for 22 weeks with three diets formulated with linseed and sunflower oils to provide ALA:LA ratios of approximately 3:1, 1:1 and 1:3. Endogenous production ofn-3 LC-PUFA was 5·9, 4·4 and 2·8 mg per g fish and that ofn-6 LC-PUFA was 0·2, 0·5 and 1·4 mg per g fish in salmon fed diets with ALA:LA ratios of 3:1, 1:1 and 1:3, respectively. The ratio ofn-3:n-6 LC-PUFA production decreased from 27·4 to 2·0, and DHA:EPA ratio increased and EPA:ARA and DHA:ARA ratios decreased, as dietary ALA:LA ratio decreased. In conclusion, with a dietary ALA:LA ratio of 1, salmon fry/parr produced about 28 μgn-3 LC-PUFA per g fish per d, with a DHA:EPA ratio of 3·4. Production ofn-3 LC-PUFA exceeded that ofn-6 LC-PUFA by almost 9-fold. Reducing the dietary ALA:LA ratio reducedn-3 LC-PUFA production and EPA:ARA and DHA:ARA ratios but increasedn-6 LC-PUFA production and DHA:EPA ratio.