Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: August 20, 2004
Publication Date: January 17, 2005
Citation: Lim, C.E., Yildirim, M., Wan, P., Klesius, P.H. 2005. Gossypol in purified and practical diets: effect on growth performance, immune responses and resistance of channel catfish ictalurus punctatus to edwardsiella ictaluri infection. Aquaculture America Conference. Technical Abstract: Free gossypol, when present in large amount in the diet, is toxic to monogastric animals, including fish. Gossypol from gossypol-acetic acid (GAA) and natural free-gossypol from glanded cottonseed meal are equally toxic to catfish but the toxicity appeared to decrease when gossypol from GAA was added to practical diets. Thus, this study was conducted to evaluate the effect of gossypol from GAA supplemented to purified or practical diets on growth performance, liver gossypol content, immune response and resistance of channel catfish (Ictalurus punctatus) to Edwardsiella ictaluri challenge. Isonitrogenous and isocaloric casein-gelatin based or soybean meal-based diets supplemented with gossypol from GAA at levels of 0, 300, 600, and 1200 mg/kg (2 x 4 factorial experiment) were each fed to juvenile channel catfish in quadruplicate aquaria to apparent satiation twice daily for 12 weeks. Weight gain (WG), feed intake (FI), and survival were significantly (P<0.05) affected by the type of diet, dietary gossypol levels and their interaction. Significant increase in WG, FI and survival were obtained in fish fed practical diets but feed efficiency ratio (FER) and protein efficiency ratio (PER) were not affected by the type of diet. Except survival, these parameters were significantly lower in the groups fed purified diets supplemented with 1200 mg/kg. Liver gossypol concentrations were linearly related to dietary levels of gossypol but the retention rate varied depending on the type of diet. At the same inclusion levels, fish fed purified diets retained significantly higher liver gossypol than in fish fed practical diets. The (+)-isomer of gossypol was predominantly retained in liver regardless of the type of diet, but the ratio of (+) to (-) gossypol isomers decreased with increasing dietary levels of gossypol. Neither the type of diet nor the level of dietary gossypol and their interaction had significant an influence on macrophage chemotaxis, serum total protein and antibody titer against E. ictaluri. Purified diets stimulated significantly higher lysosyme activity and superoxide anion production than practical diets. Fish fed purified diet containing 1200 mg gossypol/kg had significantly higher lysozyme activity than fish fed other diets. Dietary gossypol levels and the interaction between the type of diet and gossypol level had no effect on superoxide anion production. Serum complement activity was not influenced by the type of diet but the value of this parameter significantly increased with increasing level of dietary gossypol up to 600 mg/kg diet. Mortality at day 21 post-challenge with E. ictaluri was significantly lower in fish fed practical diets and fish fed the purified diet supplemented with 1200 mg gossypol/kg had the lowest mortality.