Macronutrient utilization by Atlantic halibut ( Hippoglossus hippoglossus): diet digestibility and growth of 1 kg fish

Abstract

A nine-week growth trial, followed by digestibility determinations, was conducted to study the effects of replacing dietary protein with fat and/or carbohydrate on diet utilization and growth of 1 kg Atlantic halibut. The exchange of fish meal for wheat had small, negative effects on fat digestibility. The increase in wheat content from 8 to 17% resulted in a decrease in starch digestibility from 84 to 53%. There were no significant effects of diet composition on protein digestibility. The specific growth rates (0.30±0.01% body weight/day) and the feed efficiency ratios (1.02±0.03 g gain/g dry feed) were not significantly affected by the reduction in dietary protein content from 61 to 48%. A minimum of 338 g digestible protein and 18 MJ digestible energy were used by the halibut/kg gain. Diet composition did not significantly affect the amount of protein lost in the feces per kg gain. Organic matter loss in the feces however, was greatest from the fish fed diets containing the highest level of carbohydrate.