Nonspecific immune responses, activity of digestive enzymes and body composition of rainbow trout (Oncorhynchus mykiss) fed diets containing manganese sulfate nanoparticles

The effects of dietary Manganese sulfate nanoparticles on digestive enzyme activity and non-specific immune responses for rainbow trout, (Oncorhynchus mykiss) juveniles were determined. Four-hundred rainbow trout (with an initial average weight of 0.8±0.1 g) were randomly distributed into four treatments, with three replicates and fed with four diets including a control diet (without manganese), Mn-M (containing manganese sulfate), Mn-N10 (containing 10 mg/kg manganese nanoparticles), Mn-N15 (containing 15 mg/kg manganese nanoparticles) for six weeks. At the end of the experiment, the average weight of fry fed the control diet (without manganese) was lower than other treatments and was significantly different compared to the groups fed diets containing manganese sulfate nanoparticles (P<0.05). The crude protein in juveniles fed diets containing manganese was significantly higher compared to the control group (P<0.05). Amylase, lipase and protease activity did not show statistically significant differences (P> 0.05). Plasma lysozyme activity of fish fed with Mn-N10 and Mn-N15 were significantly higher than fish fed control diet (P<0.05). Plasma complement activity was significantly higher in Mn-M compared to control treatment (P <0.05) but did not show significant difference with other treatments (P> 0.05). The results obtained in this study revealed that inclusion of manganese nanoparticles has no significant impact on activities of digestive enzymes in rainbow trout, but influences some immune responses of this spices.