Effects of dietary Russian olive, Elaeagnus angustifolia, leaf extract on growth, hematological, immunological, and antioxidant parameters in common carp, Cyprinus carpio

Abstract

In this study, the effects of dietary supplementation with Russian olive, Elaeagnus angustifolia, extract were evaluated on growth performance, antioxidant and immunological parameters of common carp, Cyprinus carpio. Hot-water extract of Russian olive leaves (RO) was added to common carp (~ 45 g) diet at 0% (C), 1% (1RO), 2% (2RO), and 3% (3RO) and offered to triplicated groups of fish for eight weeks. At the end of the feeding trial, growth performance, hematological, biochemical, antioxidant, and immunological parameters of fish were studied. The results indicated that RO supplementation had no significant effects on the fish growth performance and survival rate at any concentration. Likewise, the RO-treated fish exhibited no significant differences in red blood cell numbers, hematocrit, hemoglobin, eosinophil percentage, and monocyte percentage, compared to C treatment. Significantly higher leukocyte count and lymphocyte percentage, as well as lower neutrophil percentage were observed in 1RO treatment, compared to the other treatments. There were significant elevations in plasma alanine aminotransferase and aspartate aminotransferase activities in 3RO treatment, compared to the other treatments suggesting RO hepatotoxic effects at high concentrations. There were no significant effects of dietary RO supplementation on plasma albumin levels but 1RO treatment exhibited significantly higher plasma total protein, globulin, and lysozyme activity compared to the other treatments, suggesting an immunostimulant effect at 1% enrichment. 1RO treatment also displayed the lowest catalase activities and malondialdehyde (MDA) levels suggesting a positive effect against oxidative stress, however fish fed with 3RO displayed the highest catalase and MDA. Dietary RO supplementation exhibited no significant effects on plasma superoxide dismutase activity. In conclusion, dietary supplementation with 1% RO is recommended for carp feed formulation, as it stimulates some immune and antioxidant parameters in common carp. However, higher levels of RO should be avoided as they might cause oxidative stress and hepatotoxicity.