Cottonseed oil as a complementary lipid source in diets for gilthead seabream S parus aurata juveniles

The efficacy of using cottonseed oil ( CSO ) as a fish oil ( FO ) substitute in gilthead seabream ( S parus aurata ) juveniles feed was evaluated. Fish ( BW i 4.0 ± 2.9 g) were fed one of four isoproteic (~48% CP ) and isolipidic (~18% L) diets for 9 weeks. Added oil was either FO (control diet, CTRL ) or CSO , replacing 50% ( CSO 50 diet), 60% ( CSO 60 diet) and 70% ( CSO 70 diet) of dietary FO . Results indicated that FO replacement by CSO up to 60% level had no detrimental effects on growth or nutritive utilization and composition in fish muscles. Higher CSO intake ( CSO 70 diet, 56 g kg −1 ) led to a 16% reduction in weight gain, 14% in feed utilization ( FCR ) and 57% in muscle n‐3 long‐chain polyunsaturated fatty acids (lc PUFA ) as compared with CTRL and to abundant accumulation of lipid within the hepatocytes. Use of CSO altered fatty acid ( FA ) profiles of muscle and liver. Data suggested utilization of linoleic acid ( LOA ) by fish and retain of docosahexaenoic acid ( DHA ) in muscles. Therefore, limits of CSO inclusion as the main source of supplementary dietary lipid, with no negative effects on fish performance or nutritive composition and utilization in muscles, are: 40–48 g kg −1 feed for gilthead seabream juveniles.