Suitable dietary chitosan improves the growth performance, survival and immune function of tiger shrimp, Penaeus monodon

Different levels of dietary chitosan on growth performance, survival and stress tolerance to air exposure was studied in tiger shrimp, Penaeus monodon. Shrimp (mean initial wet weight about 1.16g) were fed with six different diets (C0, C0.05, C0.1, C0.2, C0.3 and C0.4) containing six level of chitosan (0%, 0.05%, 0.1%, 0.2%, 0.3% and 0.4% respectively) in triplicate for 60days. Growth performance [final body wet weight (FBW); weight gain (WG); biomass gain (BG)] of shrimp fed chitosan-containing diets were higher (P<0.05) than that of shrimp fed the basal diet, shrimp fed C0.1 diet showed the highest value of growth performance. Survival of shrimp in C0.1 and C0.2 diet groups were higher (P<0.05) than that of shrimp in C0, C0.05 and C0.4 diet groups but without statistical difference (P>0.05) in shrimp fed C0.3 diet group. Whole body and muscle lipid contents decreased with increasing dietary chitosan levels. Plasma total cholesterol and triglyceride contents of shrimp fed C0 diet was significantly higher (P<0.05) than that of shrimp fed chitosan-containing diets. Plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities of shrimp fed C0 diet were higher than those of shrimp fed chitosan-containing diets. Digestive gland malondialdehyde (MDA) and carbonyl protein contents of shrimp fed chitosan-containing diets were lower (P<0.05) than that of shrimp fed C0 diet. Total haemocyte count of shrimp fed C0 diet was lower (P<0.05) than that of shrimp fed chitosan-containing diets. On the contrary, the haemolymph clotting time of shrimp fed C0 diet was higher (P<0.05) than that of shrimp fed chitosan-containing diets. In conclusion, all results suggested that dietary intake containing 0.1% and 0.2% chitosan enhanced the growth of shrimp, whereas a higher level than 0.3% and 0.4% decreased growth of shrimp. Second-degree polynomial regression analysis of WG and BG indicated that the optimum supplement of dietary chitosan level should be 0.19-0.21%.