Replacement of Fish Oil with Linseed Oil or Soybean Oil in Feeds for Japanese Seabass, Lateolabrax japonicus : Effects on Growth Performance, Immune Response, and Tissue Fatty Acid Composition

A 66‐d feeding experiment was conducted to investigate the utilization of vegetable oils in Japanese seabass (initial weight: 10.09 ± 0.70 g). In experimental diets, linseed oil ( LO ) or soybean oil ( SO ) was used to replace 1/3, 2/3, and 3/3 of fish oil ( FO ) (Diets F 2 L 1 , F 1 L 2 , and LO , respectively, or Diets F 2 S 1 , F 1 S 2 , and SO , respectively). A diet with FO alone was used as the control diet. LO or SO supplementation did not reduce the specific growth rate (3.06–3.29%/d) and feed efficiency ratio (0.75–0.83) of fish, but group F 2 L 1 showed significantly better growth ( P < 0.05) and feed utilization ( P < 0.01) than group SO . Total replacement of FO with LO or SO significantly reduced certain non‐specific innate immune responses. Total replacement of FO by LO significantly increased the lipid content of fish. Concentrations of long‐chain polyunsaturated fatty acids ( LC‐PUFAs ) in whole fish and tissues were significantly reduced by LO or SO supplementation. In conclusion, LO or SO supplementations did not reduce the growth of Japanese seabass but reduced the immune responses and LC‐PUFA concentrations. LO was a better lipid source than SO for Japanese seabass in terms of fish growth and immune responses.