Submitted to: Catfish Farmers of America Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: February 21, 2003
Publication Date: February 21, 2003
Citation: Lim, C.E., Yildirim, M., Klesius, P.H., Shoemaker, C.A. 2003. Compounds in cottonseed meal other than gossypol improved the resistance of channel catfish to Edwardsiella ictaluri challenge. In: A Compiltation of Abstracts of Research on Channel Catfish. Catfish Farmers of America Research Symposium. February 21, 2003, South Destin, Florida. p.40. Technical Abstract: Two studies were conducted. Study I evaluated the effect of dietary levels of cottonseed meal (CSM) as a replacement of soybean meal (SBM) on growth performance, hematology, immune response and resistance of catfish to Edwardsiella ictaluri challenge. Results of this study showed that inclusion of 27.5 % CSM (336 mg free gossypol/kg diet) and lysine as a substitute for 50 % of SBM significantly improved weight gain and feed efficiency. Total substitution of SBM by 55.0 % CSM (671 mg free gossypol/kg diet) adversely affected these parameters. Total cell count, red blood cell count, hematocrit and hemoglobin were not affected by dietary CSM levels. Macrophage chemotaxis in the presence of E. ictaluri exoantigen was significantly higher for fish fed the 55.0 %-CSM diet as compared to those fed the lower CSM diets. Antibody titer was significantly higher for fish fed CSM-containing diets, but did not differ for those fed the 27.5 % or 55.0 %-CSM diets. Post-challenge mortality was not significantly different for the groups fed the CSM-containing diets but mortality was significantly lower than that of fish fed the CSM-free diet. Gossypol or other compounds present in CSM may have beneficial effect by improving the immune response and resistance of catfish against E. ictaluri infection. A second study was conducted to determine if dietary gossypol (0, 300, 600, 900, 1,200 and 1,500 mg/kg diet) from gossypol-acetic acid contributed to the improvement of immune response and resistance of catfish to E. ictaluri infection. Results of this study indicated that weight gain, feed efficiency, red blood cell count, hematocrit, hemoglobin and serum protein significantly decreased with increasing dietary gossypol levels. The affected concentrations varied from 300 to 1,200 mg gossypol/kg diet, depending on the parameter evaluated. White blood cell count, superoxide anion production and antibody titer were not affected by dietary levels of gossypol. Macrophage chemotaxis ratio significantly increased in fish fed the 300-mg gossypol diet but the values were similar for the groups fed diets with 300 mg/kg or higher gossypol. Serum lysozyme activity and resistance to E. ictaluri challenge were enhanced at dietary gossypol levels of 900 mg/kg or higher. Compared to the results of study I, gossypol may not be the compound responsible for enhancing the resistance of catfish to E. ictaluri infection since CSM-diets contained only 336 to 671 mg free gossypol/kg. However, synthetic gossypol (gossypol-acetic acid) and naturally occurring gossypol in CSM may be utilized differently by channel catfish. Studies to identify and evaluate other compounds in CSM responsible in improving the immune response and the resistance of juvenile channel catfish against E. ictaluri infection are needed.