EFFECT OF DIETARY LEVELS OF LIPID AND CARBOHYDRATE ON GROWTH-PERFORMANCE, BODY-COMPOSITION, NITROGEN-EXCRETION AND PLASMA-GLUCOSE LEVELS INRAINBOW-TROUT REARED AT 8-DEGREES-C OR 18-DEGREES-C

Trout reared at 8 or 18 degrees C were fed twice a day almost to satia tion with 1 of 3 experimental diets. The diets were formulated to cont ain the same levels of protein (43%, dry matter (DM) basis) and digest ible energy (around 15 kJ/g DM), but different carbohydrate/lipid rati os (30:7 to 23:14). Time-course studies of nitrogen excretion and glyc aemia were also carried out. After 12 weeks of feeding, growth, protei n retention and body composition were not influenced by the dietary tr eatment in trout reared at 8 degrees C. At 18 degrees C, the protein r etention was not affected by dietary treatment, but the weight gain te nded to be higher in trout fed the diet with the lowest carbohydrate/l ipid ratio. This result was due to higher body lipid deposition in the se trout. Nitrogen excretion was not influenced by dietary treatment, but was higher at 18 degrees C than at 8 degrees C because of a higher feed intake. Glycaemia increased with dietary level of digestible car bohydrate and the highest plasma glucose level was attained later at 8 degrees C in comparison to 18 degrees C.