| Popis: |
Furified egg white diets containing 1 or 20 mg Cu/kg and 20, 100 or 200 mg Zn/kg in a factorial arrangement were fed to triplicate groups of fingerling channel catfish (Ictalurus punctatus) in aquaria to investigate possible interactions between dietary copper and zinc. At the end of the 12-week feeding trial, weight gain and feed efficiency values of catfish fed the various diets were similar. Dietary zinc had a significant (P < 0.01) effect on hematocrit, which was generally reduced at higher levels of zinc intake. However, such a response was not observed in hemoglobin from fish fed the various diets. Dietary zinc also had a significant (P < 0.01) effect on catfish bone zinc and liver iron, but not liver zinc concentrations. Hepatic copper concentration and activities of heart cytochrome c oxidase and liver copper-zinc superoxide dismutase (SOD) were significantly (P < 0.05) reduced in catfish fed 1 mg Cu/kg compared to those fed 20 mg Cu/kg, while manganese SOD showed a compensatory increase in activity at low copper intake. Based on these enzyme activities as well as hemoglobin and tissue mineral concentrations, increasing levels of dietary zinc did not affect copper bioavailability. Therefore, supplementation of high levels of zinc in practical diets should not impair the copper status of channel catfish. |
