Requirements of n-3 Highly Unsaturated Fatty Acids in Beluga (Huso huso) Juvenile and their Effects on Growth, Carcass Quality and Fatty Acids Composition

An 8-week feeding experiment was carried out on beluga (Huso huso) juvenile to evaluate the effects of different levels of fish oil containing n-3 highly unsaturated fatty acids (n-3 HUFAs) on fish growth and fatty acid composition. The requirements of beluga juvenile for n-3 HUFAs were studied by feeding fish diets containing six different levels of n-3 HUFAs ranging from 1.56 to 17.25% (% 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> 0.05). There were no significant differences among plasma protein, glucose, cholesterol and triglyceride contents of dietary treatments (P> 0.05). However, haematocrit values were significantly lower in diets 1 and 2 (P< 0.05). 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-3 HUFAs reflected the dietary fatty acid composition. The n-3 HUFAs contents of the lipids of fish increased with an increase in dietary n-3 HUFAs levels. Results suggested that minimum levels of n-3 HUFAs in diet have no effect on growth and n-3 HUFAs are not a restrictive factor on growth in beluga.