Submitted to: Global Aquaculture Advocate
Publication Type: Popular Publication
Publication Acceptance Date: 6/8/2004
Publication Date: 7/30/2004
Citation: Lim, C.E., Yildrim-Aksoy, M., Klesius, P.H. 2004. Dietary gossypol is of little or no benefit in improving the resistance of channel catfish to edwarsiella ictaluri infection. Global Aquaculture Advocate. Interpretive Summary:
Technical Abstract: A study was conducted to evaluate the effect of dietary levels of gossypol from gossypol-acetic acid on growth, liver gossypol content, hematology, immune response and resistance of channel catfish to E. Ictaluri. A basal purified diet supplemented with 0, 300, 600, 900, 1200 and 1500 mg gossypol/kg diets were fed to juvenile channel catfish in quadruplicate aquaria to apparent satiation twice daily. Final weight gain was inversely related to the levels of dietary gossypol. Feed intake and feed efficiency were a reflection of weight gain. Survival was not affected by dietary gossypol levels. Body moisture increased whereas body fat decreased with increasing dietary gossypol concentrations. Body protein significantly decreased in fish fed the 1500-mg gossypol diet. Gossypol concentration in liver was linearly related to dietary levels of gossypol. Ratio of (+) to (-) gossypol isomers in liver of fish fed different diets was relatively constant. Red blood cell count of fish fed the two highest levels of dietary gossypol (1200 and 1500 mg) was significantly lower than those of fish fed the control diet. Hemoglobin significantly decreased in fish fed 900-mg or higher gossypol diets. Hematocrit was significantly affected at each incremental level of dietary gossypol of 600 mg/kg or higher. Serum protein did not differ for fish fed the three lowest dietary levels of gossypol but was significantly reduced at 900 mg or higher gossypol. Macrophage chemotaxis ratio was similar for groups fed diets containing gossypol but was significantly higher than that of fish fed the control diet. Serum lysozyme activity significantly increased at dietary gossypol levels of 900 mg or higher. Superoxide anion production did not differ among treatments. Mortality 14-day post challenge with E. ictaluri significantly decreased at dietary gossypol levels of 900 mg or higher. However, antibody titer against E. ictaluri 15-day post-challenge was not affected by dietary treatment. This study indicates that juvenile channel catfish were more sensitive to gossypol toxicity than previously reported.