مشخصات پژوهش

An 8-week study was carried out to examine the influence of dietary Biotronic Top3 (BTT3), which is a blend of short-chain fatty acids (formate, propionate, and acetate), a phytogenic agent (cinnamaldehyde), and a permeabilizer complex (Biomin), in whiteleg shrimp (Penaeus vannamei) juveniles. Five isonitrogenous (∼38%) diets were formulated and supplemented with BTT3 at 0 (control), 0.3, 0.6, 0.9, or 1.2 g/kg. Shrimps (2.7 g) were allocated into 15 circular fiberglass tanks filled with 150 L seawater (20 shrimp per tank) and each dietary treatment was in triplicate. Shrimps were handfed thrice a day at the rate of 7% of their initial biomass for 8 weeks. At the end of the feeding trial, hemolymph and hepatopancreas (HP) were sampled to evaluate plasma biochemical factors, immune-related genes, and digestive enzymes, respectively. The growth rate in shrimps fed with a 0.3 g BTT3/kg diet was markedly higher (∼1.6 g) than in the control (P < 0.05), but higher dietary BTT3 levels did not improve growth and feed utilization. Protein deposition in the whole body of shrimps fed with 0.3 or 0.6 g BTT3/kg diets was significantly increased (∼1.5%) compared to the control. Total alkaline proteases activity in BTT3 groups was significantly higher than in the control. The activity of antioxidant enzymes, including catalase, superoxide dismutase, and glutathione peroxidase, was increased in HP of shrimps fed BTT3-supplemented diets; meanwhile, malondialdehyde level was significantly reduced by increasing dietary BTT3 level. Shrimps fed diets supplemented with 1.2 g BTT3/kg, and the control had the highest and lowest plasma phenoloxidase activity, respectively. The plasma alkaline phosphatase content in BTT3 groups was higher than in the control. The highest relative abundance of prophenoloxidase gene mRNA transcript was in HP of shrimps fed a 1.2-g BTT3/kg diet. The relative abundance of lysozyme and penaeidin-3α genes mRNA transcript in HP of shrimps fed 0.9 and 1.2 g BTT3/kg d