Macronutrient composition of
formulated diets for Atlantic halibut (Hippoglossus hippoglossus, L.)
juveniles
K. Hamre, A. Øfsti, T. Næss, R. Nortvedt, J.Chr.
Holm
Aquaculture, 227(1-4): 233-244
Abstract:
A three component mixture design was used to
investigate the optimum composition of macronutrients for Atlantic halibut
juveniles (0.5 g startweight). Protein, lipid and carbohydrate were varied
between 530–830, 50–300 and 0–150 g kg-1 dry wt.,
respectively. Of the 21 diets, 20 produced were fed to fish in single tanks,
while 1 diet was fed to fish in four replicate tanks to estimate inter-tank
variation. The experiment lasted for 2 months.
Carbohydrate levels above 50 g kg-1 were
suboptimal for the halibut as seen from lowered specific growth rates (SGR),
increased hepatosomatic indices and accumulation of carbohydrate in the
liver. At low carbohydrate levels (0 and 50 g kg-1), the specific
growth rates appeared similar with lipid levels between 50 and 250 g kg-1,
while 300 g lipid kg-1 resulted in growth depression. At higher
carbohydrate levels, fish growth was reduced with lipid levels increasing
above 100 g kg-1. It can be concluded that Atlantic halibut
juveniles have low tolerance to dietary carbohydrate, whereas dietary lipid
can be varied over a wide range without affecting growth performance. Based
on the limits of 50 g kg-1 for carbohydrate and 250 g kg-1
for lipids, the protein requirement appears to be at least 630 g kg-1.
(Institute of Nutrition, Directorate of Fisheries,
P.O. Box 185, N-5804, Bergen, Norway, e-mail: kristin.hamre@nifes.no)