Influence of dietary oil content on the growth and chemical composition of Atlantic salmon (Salmo salar)

Two extruded diets with oil/protein levels of 260/410 and 360/365 g kg(-1) were used to feed Atlantic salmon, from an initial weight of 600 g to a final weight of 4 kg after 1 year of feeding. The experiment was performed using 12 net-pens with 500 fish in each. Every 4 months 10 fish were taken from each net-pen, and analysed for growth and proximate composition. After 4 months of feeding, the chemical composition in the fillets was significantly different for the two different feed groups. The mean fillet fat content was 1% higher in fish fed with high oil content in the feed. There were no differences in the biological values. After 8 months of feeding the difference in mean muscular fat content was 3%, but there was still no difference in the carcass weight. However, a significant difference was found in the intestine weight and the condition factor. One year of feeding resulted in a significant, 10% higher carcass weight, a 2% higher fat-content and a 1% lower protein-content in the fillets of fish fed on the high oil content diet. A drop in pH was found during the winter, but this was not correlated to the feed.