Pyridoxine acts as a coenzyme in many reactions involved in the nutrient metabolism . It is an essential nutrient to maintain and enhance the growth performance, immunity and antioxidant capacity of aquatic animals including fish and shrimp. T his study was designed to determine the optimal level pyridoxine in diet for Pacific white shrimp.
A control (Con ) diet was formulated to have a low crude protein level (33%) without pyridoxine supplementation. A negative control (Con-) diet was formulated with 0.4% tetracycline hydrochloride for the evaluation of the effects of pyridoxine synthesis by intestinal microorganism in the shrimp. Six other diets were prepared by adding pyridoxine at 25, 50, 75, 100, 125 and 150 mg/ kg to Con diet (designated as P25, P50, P75, P100, P125 and P150, respectively). Each diet was randomly assigned quadruplicate groups of each 20 shrimp (0.38±0.00 g) and fed for 45 days.
The growth performance was significantly increased by pyridoxine supplementation in diets. The d ietary pyridoxine improved the innate immunity and antioxidant capacity of shrimp. The highest activities of trypsin, chymotrypsin, lipase and amylase were observed in shrimp fed P75 diet. Cell membrane thickness was significantly increased in all the pyridoxine supplemented groups, except for P25 and P150, than in Con group. Gene expression was significantly upregulated in cystathionine-β-synthase, cystathionine-γ-lyase, pyridoxal kinase and crustin up to P75 group. The broken line regression analysis indicated that t he optimum pyridoxine level of a low protein diet seems to be 75.7 mg/kg diet based on