Effects of dietary vitamin E and C co-supplementation on growth performance, hemato-immunological indices, digestive enzymes activity, and intestinal histology of rainbow trout fed diet contained spoiled fish meal and oil

Abstract

An eight-week feeding trial was conducted to elucidate the effects of diets containing oxidized fish oil (OFO) and/or spoiled fish meal (SFM) supplemented with various contents of vitamins E (VE: 100 and 200 mg/kg) and C (VC: 200 and 400 mg/kg) on some selected physiological parameters of juvenile rainbow trout, Oncorhynchus mykiss. The growth indices were affected by OFO and SFM-contained diets; the lowest values were observed in those fish raised on diet containing OFO and high levels of the vitamins. In all experimental groups, the hematological parameters (erythrocytes, leukocytes, hematocrit, and hemoglobin) were increased compared to the control group, and higher values were recorded in group fed OFO+VE (200 mg/kg) +VC (400 mg/kg)-supplemented diet (P < 0.05). A significant increase in serum lysozyme activity, immunoglobulin content, and complement pathway, was observed in fish fed OFO or SFM-contained feeds compared to the control group (P < 0.05). Digestive enzyme activities were mainly affected by dietary OFO contents, where the highest activities were detected in fish fed contained OFO and the vitamins (P < 0.05). According to the histological results, vitamin supplementation of OFO or SFM contained diets, especially at higher concentration, effectively reduced intestinal tissue damage (P < 0.05). In conclusion, VE and VC supplementation could mitigate the adverse effects of dietary OFO or SFM (e.g., decreased fish performance or health) by improving physiological responses of rainbow trout.