Effect of chitosan on common carp (Cyprinus carpio) fry growth performance, feed utilization and nutriphysiological status

The aim of research was to analyse the impact of chitosan supplementation (1% and 2% doses) on the nutriphysiological status (selected blood biochemical indicators, the microstructure of the intestine and liver and the mineral profile in the meat of common carp (Cyprinus carpio) fry (average 63 ± 4.9 g). The experiment was carried out with four replications per treatment, with 48 fish per tank in an open flow system. The average water temperature during the experiment was 20.7 °C, with a range from 18.0° to 22.8°C. The average water dissolved oxygen level was 4.6 mg dm−3 with a range of 4.0–6.2 mg dm−3. Experimental diets contained crude protein (37.5%) and crude fat (8.9%). There were no statistically significant differences between groups within the analysed growth and feed utilization parameters. As the blood analysis showed, chitosan supplementation significantly influenced (P < 0.05) the levels of total cholesterol (TCH), low-density lipoprotein (LDL), alkaline phosphatase (ALP), iron (Fe) and phosphorus (P). The 2% chitosan led to a reduction in the Fe level in the meat, and dietary supplementation with chitosan at both doses caused a significant increase (P < 0.05) in the concentration of Cu in this tissue. This confirms the properties of chitosan as a dietary fibre that inhibits the absorption of Fe in the intestine by reducing its bioavailability for mucosal cells. A significant increase (P < 0.05) in crypt depth and muscular layer thickness was observed with the increase in dietary chitosan. Histopathological examination of the liver showed significant differences in hepatocyte vacuolization between groups supplemented with 2% chitosan and the control. Only mild to moderate pathological changes and no severe pathological changes were observed between the experimental groups. The obtained results indicate that the chitosan used in the experiment showed both prebiotic and dietary fibre properties.