The influence of dietary carbohydrate and protein levels on energy and nitrogen utilization of Atlantic salmon in seawater

A 10-week comparative slaughter and metabolism trial was conducted with Atlantic salmon. Four experimental diets were used in which the protein and carbohydrate contents were altered by substituting fish meal with wheat starch. Feed intake was similar in all groups, but both specific growth rate and feed efficiency ratio improved as the dietary protein content increased. The nitrogen budget showed that, per kg gain, nitrogen intake was positively related to the dietary protein content. This was again reflected in the content in the whole body, resulting in no change in percentage nitrogen retention. Heat increment increased linearly with increasing carbohydrate content in the diet. There was no effect of treatment on the level of non-faecal nitrogenous losses and, thus, the results indicate that the increase in heat increment was caused by the increase in dietary carbohydrate level.