Effect of dietary fat level and exercise on growth, feed utilization, nutrient digestibility and fat deposition in Atlantic salmon (Salmo salar L.)

The aim of the present study was to investigate the effects of dietary fat level and exercise on growth, feed utilization, nutrient digestibility and fat deposition in farmed Atlantic salmon (Salmo salar L.). Atlantic salmon (1409 ± 43.3 g) were reared for 97 days in net pens in sea water with water temperatures ranging from 8.9 to 5.5oC and natural photoperiod. The experiment was designed as a 2x2 factorial design with water current (high and low) and fat level (high and low) as the main factors. The feeds were formulated with a mixture of fish oil and rapeseed oil (50:50) to obtain low fat (250 g kg-1) and high fat (350 g kg-1) diets. Fish were individually marked with PIT-tag and distributed into total 12 net pens (100 fish/pen). The results showed that high fat diets had higher diameter and lower Doris durability than the low fat diets. High fat diet also showed a significantly higher digestibility of dry matter, fat and energy. No significant effect of diet was observed on body composition or fat deposition in liver, heart, visceral fat and white muscle. The numerical values showed a higher fat content in organs from fish fed high fat diets. High water current showed improved weight gain and growth rate as well as feed utilization. No differences were observed in organo-somatic index (OSI), proximate chemical composition of the body or fat deposition in organs and white muscle. Fat digestibility was lower in salmon from high current. No other differences in nutrient digestibility were noted. Growth tended to be highest in fish fed high fat diet and kept at high current. These results suggest that training in combination with high fat diet improve productivity at the fish farm