Growth response, body composition, plasma metabolites, digestive and antioxidant enzymes activities of Siberian sturgeon (Acipenser baerii, Brandt, 1869) fed different dietary protein and carbohydrate: lipid ratio

Knowing the effect of dietary nutrients on physiological parameters, especially oxidative stress, during fish rearing can be useful to improve fish health and optimize production in aquaculture. In this study, four iso-energetic (2 x 2 factorial design) diets differing in nutrient composition were submitted to the Siberian sturgeon juveniles, to analyse biochemical and physiological responses. The juveniles were fed for as long as 10 weeks with the following diets: low protein-high carbohydrate (CHO): lipid ratio (LP-St), high protein-high CHO: Lipid ratio (HP-St), low protein-low CHO: Lipid ratio (LP-L) and high protein-low CHO: Lipid ratio (HP-L). It was shown that HP-L diet significantly induced higher growth performance in the juveniles than LP-L; however, there was not a significant difference between them with other treatments. HSI was increased by higher dietary CHO: L ratio. The result obviously showed the higher dietary fat led to an increase in sturgeon body fat content. In addition, dietary protein and CHO: lipid ratio significantly affected plasma metabolites (glucose, cortisol, cholesterol and triglyceride) but did not affect IGF-1 and insulin levels. Based on enzyme activities results, incorporation of high protein (44%) in the diet induced lower amylase activity and carbohydrate digestion in the sturgeon juveniles. Moreover, antioxidant enzyme activities in this species were more influenced by lipid than other nutrients. In conclusion, using appropriate carbohydrates (similar to 30%) in the sturgeon diet helps to spare protein. Furthermore, it is suggested to decrease the amount of lipid in high protein diet, to improve higher sturgeon fillet quality and less oxidative damage in liver.