Dietary copper requirement of fingerling channel catfish

Purified egg white diets containing incremental levels of copper (as CuSO₄·5 H₂O) were fed to fingerling channel catfish (Ictalurus punctatus) to determine their dietary copper (Cu) requirement. Catfish in aquaria were fed diets containing 0, 2, 4, 6, 8 or 10 mg of supplemental copper/kg diet for 13 weeks. Growth and feed efficiency data, as well as hemoglobin, hematocrit and erythrocyte count values were similar for catfish fed the basal diet which contained 0.89 mg Cu/kg diet and all copper-supplemented diets. A diet containing 40 mg of supplemental copper/kg was also fed in this experiment since 16 and 32 mg of supplemental copper/kg had previously been reported to cause suppressed growth of channel catfish. Those fed the 40 mg of supplemental copper/kg diet had similar growth and feed efficiency values as catfish fed the other diets. At the end of week 13, heart cytochrome c oxidase and liver copper—zinc superoxide dismutase activities were significantly reduced in catfish fed diets containing 0 and 2 mg of supplemental copper/kg as compared to those fed 4 mg/kg or more of supplemental copper. Based on the enzymatic data, the minimum dietary copper requirement of channel catfish was determined to be approximately 5 mg of total copper/kg diet.