Response of juvenile Japanese seabass (Lateolabrax japonicus) to different dietary fatty acid profiles: Growth performance, tissue lipid accumulation, liver histology and flesh texture

A 10-week feeding experiment in offshore floating cages was conducted to investigate the effects of dietary fatty acid profiles on growth, tissue lipid accumulation, liver histology and flesh texture of juvenile Japanese seabass (mean initial weight 29.53 +/- 0.86 g). Six low-fish meal diets were prepared with different lipid sources (10% in the diets), each with a characteristic fatty acid: Diet MCA: medium-chain fatty acid, C8:0 + C10:0; Diet PA: palmitic acid, C16:0; Diet SA: stearic acid, C18:0; Diet OA: oleic acid, C18:1n-9; Diet LNA: alpha-linolenic acid, C18:3n-3; Diet N-3 LC-PUFA: n-3 LC-PUFA, DHA + EPA. A diet with 10% fish oil was used as the control diet (Diet FO). Each diet was fed triplicate groups of 30 fish. The results showed that the compared to group FO, the final body weight (FBW), specific growth rate (SGR) and feed efficiency ratio (FER) were significantly reduced in groups MCA, PA, and SA, but not in groups OA, LNA, and N-3 LC-PUFA. The feed intake (FI) in group MCA was much lower compared to other groups, while group PA showed the highest FI, significantly higher than that in group N-3 LC-PUFA. Diets MCA, PA, and SA leaded to much lower lipid content in muscle, gut, and whole fish body, while the liver lipid content was significantly higher in groups PA, SA, OA, and LNA than that in groups FO, MCA, and N-3 LC-PUFA. Obvious hepatocytes swelling, lipid vacuolization and nucleus polarization were observed in liver from groups OA, SA, PA, and LNA, while in group MCA, the hepatic tissue was in disorder with indistinguishable hepatic cell outline and dissolved nuclei. Fish fed MCA, PA, and SA tended to have firmer flesh than fish fed OA, LNA, and N-3 LC-PUFA. These results showed that Japanese seabass has a relatively high tolerance to oils rich in C18:1n-9 and C18:3n-3 but high levels of C16:0 or C18:0 enriched lipid sources could reduce the feed efficiency and growth rate. High levels of medium chain fatty acids (C8:0 and C10:0) in the diets could drastically reduce the feed intake. All the alternative lipid sources leaded to impairment to liver histology and modified the flesh texture, probably via altering tissue lipid concentrations. Statement of relevance: This study provided useful data for the application of a range of alternative lipid sources in fish feed. Also, the present results are helpful in formulating a balanced dietary fatty acid profile for Japanese seabass. (C) 2016 Elsevier B.V. All rights reserved.