Effect of chitosan diet on intestinal histology, body composition and salinity and thermal stresses resistance in Caspian kutum (Rutilus frisii kutum, Kamenskii 1901) fingerlings

This study was conducted to evaluate the effect of chitosan diet on intestinal histology, body composition and salinity and thermal stresses resistance in Caspian kutum (Rutilus frisii kutum) fingerlings was performed. This research, using completely randomized design consisting of three levels 0.25, 0.5, 1, and 2 gr of chitosan per kg of Caspian kutum commercial diet was designed with three replications. Kutum fingerlings weighted average 1.76 ± 0.15 g were fed with the experimental diets for 8 weeks. At the end of experiment, tissue sections were prepared of the fish intestinal by cutting with a thickness of 5 mm. For evaluate the resistance to stresses salinity and thermal fingerlings were divided under salinity stress 11 ppt and 13 ppt and temperatures 30 °C and 34 °C, and survival rate were calculated. Microscopic observations showed that the intestinal villi height in fish fed diet containing 1 g kg-1 of chitosan significantly increased to 319.93 µm compared to the control group (P0.05). Fish survival rate after 11 ppt and 13 ppt salinity stress showed no statistically significant difference (P>0.05), but the survival rate of fish fed diet containing 1g kg-1 of chitosan after the 34 °C thermal stress significantly increased to 70% (P