Diet, size and location as determinants of n-3 long-chain polyunsaturated fatty acid content in farmed Atlantic Salmon (Salmo salar )

Abstract

We explored how currently manufactured feeds, under real-world conditions and across geographically distinct locations, promoted flesh n-3 long-chain polyunsaturated fatty acid (LC-PUFA, i.e. 20:5n-3 + 22:6n-3) levels in various life stages of farmed Atlantic Salmon (Salmo salar). Potential effects on flesh LC-PUFA included: (1) diet and fish weight at one Canadian east coast farm, (2) diet and farm location across six east coast farms, and (3) diet and farm location between east and west coast farms. For objectives 1 and 2, salmon were fed a currently manufactured feed (labelled as feeds A, B or C) and harvested at 1, 3 and 5 kg. LC-PUFA levels in 5 kg (harvest size) fish were then compared to previously published values for west coast farmed Atlantic Salmon (Obj. 3). Combined results revealed that variability in LC-PUFA levels was better explained by diet than by fish weight or farm location. Fish size, however, was also important for two reasons. First, feeding a high LC-PUFA diet early in life appeared important for ensuring high LC-PUFA levels at harvest size. Second, salmon flesh LC-PUFA levels increased with fish size, but only when dietary LC-PUFA was provided above an apparent threshold value (~3000 mg per 100 g or 10% of total fatty acids) that likely promoted LC-PUFA incorporation and storage. Overall, our comparison makes new recommendations for feed manufacturers and demonstrates that farmed Atlantic Salmon reared under real-world conditions on currently available salmon feeds were good sources of n-3 LC-PUFA to consumers.