Effect of dietary protein level on growth and carcass composition in Atlantic halibut (Hippoglossus hippoglossus L)

The effects of replacing increasing levels of protein with carbohydrate or lipid in diets for halibut were studied in three consecutive long term experiments, The fish were fed nine different dry pelleted diets with ranges of protein, carbohydrate and lipid from 410-719, 14-269 and 126-325 g kg(-1) diet, respectively. The experiments started with 5-7 g fish and lasted for 14 and 17 months until the fish reached 400-600 g. All groups showed good growth and feed efficiencies during the experimental periods, with daily specific growth rates of 0.87-1.04% and feed efficiencies (fish weight gain/feed offered) ranging from 0.99 to 1.50, At 250 g kg(-1) lipid diet, a significant increases in growth and feed efficiency was observed when dietary carbohydrate was decreased from 269 to 31 g kg(-1) diet with concomitant increases in dietary protein from 410 to 618 g kg(-1) diet, At high dietary protein level, increasing the level of lipid in the diet from 127 to 325 g kg(-1) diet, resulted in higher carcass lipid levels ranging from 72.5 to 125 g kg(-1) body weight respectively. No difference in growth or feed efficiency was found with increasing dietary lipid levels.