Effect of dietarySchizochytriumsp. oil as an n-3 long-chain polyunsaturated fatty acid source on growth performance, lipid metabolism and antioxidant status in juvenile grass carp (Ctenopharyngodon idellus): A comparative study with fish oil

Four isonitrogenous and isoenergetic semi-purified diets including control group (excluding n-3 long-chain polyunsaturated fatty acid [n-3LC PUFA]), fish oil group (FO),Schizochytriumsp.-stearin oil group (SO) andSchizochytriumsp.-wax grease oil group (WGO) (all three groups containing 0.52% n-3LC PUFA) were prepared to feed grass carp for 56 days. Compared with the control, dietary FO, SO and WGO significantly promoted growth performance, increased the level of n-3 LC PUFA which was preferentially deposited in polar lipids in muscle. FO, SO and WGO groups had the same effects on inhibiting the crude lipid content of whole fish, decreasing the size of adipocytes and up-regulated mRNA expression of adipose TAG lipase (ATGL) in the adipose tissue, as well as obviously down-regulated mRNA expression of glutamate dehydrogenase (GLDH) in muscle. Interestingly, the content of crude protein in muscle and whole body was increased in SO group rather than FO group compared with control, and the expression of GLDH in SO group was lower than that in FO group in muscle. These results may contribute to the effects of lipid-lowering, protein deposition increasing and growth improvement of SO group. Overall, SO group exhibited better growth performance than FO group.