Nucleotide supplementation in the diet of Sterlet sturgeon (Acipenser ruthenus): Improved zootechnical performance, biochemical indices, and immune responses

Abstract

Nucleotides (NT) are low-molecular-weight intracellular compounds which play pivotal roles in physiological activities of fish. The present study was conducted to determine the effect of dietary NT supplementation on performance, body composition, serum biochemical properties and innate immune responses of Sterlet sturgeon (Acipenser ruthenus). Five semi purified experimental diets containing graded levels of NT (0.00%, 0.15%, 0.25%, 0.35%, and 0.50%) from Vannagen, a commercial NT product, were fed to triplicate groups of Sterlet sturgeon with an initial average weight of 95.33 ± 1.23 g in a flow-through system for 10 weeks. The fish were fed by hand to apparent satiation six times daily (04.00, 08.00, 12.00, 16.00, 20.00 and 24.00 h). The results corroborated that dietary NT supplementation linearly improved the weight gain ratio (WGR), specific growth rate (SGR), feed efficiency (FE), and protein efficiency ratio (PER) in Sterlet sturgeon after 10-week administration (p < 0.05). A quadratically increasing trend of crude protein and fat content was also observed by dietary inclusion of 0.25% NT with the highest values of 237.90 ± 0.17 and 79.55 ± 2.05 g kg-1 in fish fed with 0.35 NT supplemented diet, respectively (p < 0.05). Nucleotide inclusion produced a significantly linear increase in serum biochemical parameters with the highest level of total protein (34.67 ± 0.80 g L−1), albumin (10.00 ± 0.10 g L−1), and globulin (24.66 ± 0.71 g L−1) in fish fed with 0.50% NT supplemented diet (p < 0.05). Measured stress responses including cortisol and glucose levels were also linearly (p < 0.05) and quadratically (p < 0.05) reduced after feeding with different dietary NT concentrations, respectively. Sterlet sturgeon fed a diet containing 0.35% exogenous NT showed the highest immune responses including lysozyme activity (LA) (40.67 ± 2.60 U mL−1), immunoglobulin M (IgM) (62.00 ± 1.73 mg dL−1), complement component C3 (65.30 ± 4.81 mg dL−1), and complement component C4 (8.73 ± 0.50 mg dL−1), which were significantly higher than those fed the basal diet (p < 0.05). It can be concluded that dietary NT supplementation has positive effects on growth performance, feed utilization, body composition, biochemical parameters and immune responses of Sterlet sturgeon. Based on the whole body crude protein content, serum total cholesterol and triglycerides concentrations, LA as well as complement component C3 and C4, the optimal level of dietary nucleotide supplementation for Sterlet sturgeon was estimated to be in a range of 0.263–0.383% of diet.