Dietary thiamine supplementation enhances the growth performance, digestive enzyme activity, intestine development, immunity and anti-inflammatory gene expression of juvenile olive flounder (Paralichthys olivaceus)

This research aimed to determine the dietary requirement of thiamine and evaluate its effects on olive flounder (Paralichthys olivaceus). Control diet (Con) was formulated without thiamine supplementation, while four additional diets were formulated with thiamine concentrations of 4, 8, 12 and 16 mg/kg diet (designated as T4, T8, T12 and T16, respectively). A total of 300 fish (initial weight, 55.5 ± 1.3 g) were randomly distributed into 15 tanks (triplicate groups per treatment, 20 fish per tank) and fed for 10 weeks. One-way ANOVA was performed to analyze treatment effects. Final body weight was significantly increased in all the thiamine-supplemented groups compared to the Con group. Significant improvements in weight gain, specific growth rate and feed utilization were observed in T4 and T16 groups compared to the Con group. Immune responses, including anti-protease, lysozyme and myeloperoxidase activities and total immnunoglobulin concentration were significantly increased in the T4-T12 thiamine-supplemented groups. Antioxidant activity was significantly increased in all thiamine-supplemented groups. Trypsin activity was significantly elevated in the 4–12 mg/kg groups, while amylase and lipase activities were enhanced in all thiamine-supplemented groups. Anti-inflammatory genes were significantly upregulated in thiamine-supplemented groups compared to the Con. Thiamine supplementation promoted an increase in goblet cell count and villi length in intestine. A broken-line regression analysis for weight gain indicated that the optimal thiamine requirement for olive flounder would be 3.05 mg/kg diet. These findings demonstrate the positive effects of dietary thiamine on growth, immunity, antioxidant activity, digestive enzyme activity and intestinal health in olive flounder.