R. Asadi - Fisheries Department, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Islamic Republic of Iran.
M. R. Imanpoor - Fisheries Department, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Islamic Republic of Iran.
B. Dastar - Department of Animal Science, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Islamic Republic of Iran.

An ۸-week feeding experiment was carried out on beluga (Huso huso) juvenile to evaluate the effects of different levels of fish oil containing n-۳ highly unsaturated fatty acids (n-۳ HUFAs) on fish growth and fatty acid composition. The requirements of beluga juvenile for n-۳ HUFAs were studied by feeding fish diets containing six different levels of n-۳ HUFAs ranging from ۱.۵۶ to ۱۷.۲۵% (% of total fatty acids). Weight gain, feed conversion ratio, condition factor, specific growth rate and protein efficiency ratio were not significantly different among dietary treatments, nor was the body composition (including: moisture, protein, lipid and ash) of beluga juvenile (P> ۰.۰۵). There were no significant differences among plasma protein, glucose, cholesterol and triglyceride contents of dietary treatments (P> ۰.۰۵). However, haematocrit values were significantly lower in diets ۱ and ۲ (P< ۰.۰۵). The fatty acid composition of fish showed a pronounced change from the initial carcass with fatty acid composition changes in experimental diets. The fatty acid composition of the beluga carcass fed on diets containing various levels of n-۳ HUFAs reflected the dietary fatty acid composition. The n-۳ HUFAs contents of the lipids of fish increased with an increase in dietary n-۳ HUFAs levels. Results suggested that minimum levels of n-۳ HUFAs in diet have no effect on growth and n-۳ HUFAs are not a restrictive factor on growth in beluga.

Canola oil, DHA, EPA, Fish oil, Oil