Effects of dietary lipid and protein levels on growth and physiological metabolism of Pelteobagrus fulvidraco larvae under recirculating aquaculture system (RAS)

A feeding trial was conducted to investigate the effects of different dietary lipid and protein levels on both the physiological metabolism and the anti-oxidation of Pelteobagrus fulvidraco larvae cultured in recirculating aquaculture system (RAS). In the present study, four test diets (P52L13, P52L9, P48L13, P48L9) were formulated by two different lipid levels (13%, 9%) and two different protein levels (52% and 48%) in a factorial manner (2 × 2) to provide four different dietary protein-lipid ratios (P:L) 3.95, 5.71, 3.56 and 5.46. Each treatment was assigned in triplicate. Two days after hatching, larvae were fed with Artemia sp. for 1 day, and then were co-fed the Artemia sp.plus the tested diets for 2 days, finally fed test diets for 18 days. The results were in keeping with that of growth performance, showed that the larvae fed on P52L13 and P48L9 diets had significantly higher activities of lipoprotein lipase (LPL), glutamic-pyruvic transaminase (GPT), superoxide dismutase (SOD) and catalase (CAT) than other two groups (P < 0.05). The highest activities of lysozyme (LZM) and glutathione (GSH) were observed in group P52L13 and P48L9, respectively (P < 0.05). Concerning dietary lipid levels, the highest activities of LPL, GOT, SOD, CAT and LZM were observed for larvae fed diets containing 13% lipid (P < 0.05). Regarding to antioxidative factors, same trend was observed for larvae fed diets with 52% protein (P < 0.05). Our results clearly suggested that P52L13 and P48L9 diets could promote the metabolism of protein and lipid, and antioxidative ability of P. fulvidraco larvae in RAS, meanwhile, P52L13 diet is the superior.