Effects of replacing dietary fish oil with beef tallow on growth performance, serological parameters, and fatty acid composition in juvenile olive flounder, Paralichthys olivaceus

This study evaluated the effects of replacing fish oil (FO) with beef tallow (BT) in juvenile olive flounder, Paralichthys olivaceus (3.93 ± 0.07 g), over 8 weeks. Seven diets, consisting of 0, 25, 50, 75, and 100% replacement of FO with BT and 63 and 75.9% replacement supplemented with docosahexaenoic acid (DHA) at 0.9 and 1.1% of 100 g diet, respectively, were distributed into 21 tanks in a semi‐recirculation system with 15 fish per tank. The replacement of FO with BT at the given levels showed no significant changes (p > .05) in growth performance and whole‐body proximate composition. Fish fed the diet of 75.9% replacement with 1.1% DHA supplementation showed the best performance in these measurements among the treatments. Plasma glutamic pyruvic transaminase, cholesterol, high‐ and low‐density lipoproteins, and total protein were not significantly influenced by the replacement of FO with BT. The FO replacement generally resulted in a reduction of eicosapentaenoic acid, DHA, and n‐3/n‐6 polyunsaturated fatty acid ratio in the whole body, whereas the DHA supplementation recovered the level of DHA and the n‐3/n‐6 ratio to those observed in the group fed the 0% replacement diet. Taken together, BT along with DHA supplementation can potentially be a cost‐effective alternative for FO in olive flounder culture