Effect of dietary Gracilaria lemaneiformis on growth performance, fatty acid composition, immunity and intestinal histology of red drum (Sciaenops ocellatus)

We investigated the effect of dietary graded level of Gracilaria lemaneiformis on the growth performance, fatty acid composition, body composition, immunity and intestinal histology of red drum (Sciaenops ocellatus) initial weight (9.38±0.06) g.Six isoproteic and isolipidic diets (crude protein: 41%;crude fat: 10%) were formulated containing 0%, 1%, 2%, 3%, 4% and 5% G. lemaneiformis. After eight weeks of feeding, no significant difference was found in survival, weigh gain (WG) and specific growth ratio (SGR) (P>0.05), but weight gains in 1%~4% groups were higher than that in the control whereas 1% group had the highest feed efficiency and SGR among all treatments. The concentrations of docosahexaenoic acid (DHA) were significantly higher in 5% group than that in the control (P < 0.05). Meanwhile, the liver superoxide dismutase (SOD) in 4% group was significantly higher than that in the control (P < 0.05);well-developed intestinal villi was presented in 3% addition group. The results indicate that dietary supplementation of G. lemaneiformis can improve the growth as well as liver and intestinal health, increasing whole fish DHA content.