Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/12/2003
Publication Date: 12/15/2003
Citation: Lim, C.E., Li, M.H., Robinson, E. 2003. Cottonseed meal in fish diets. Meeting Abstract. Interpretive Summary:
Technical Abstract: Cottonseed meal (CSM), because of its availability, nutritional value, high protein content, palatability and low-cost, is a good alternative protein source to fish meal in fish diets. The amount of CSM that can be included in fish diets depends primarily on the levels of free gossypol and available lysine. Because free gossypol is bound to lysine during the processing of cottonseed into meal, lysine availability decreases as free gossypol decreases. Available data indicate that, dependent on the species, solvent-extracted CSM at levels of 10 to 30% can be used in fish diets without detrimental effects. At this level of inclusion, supplementation of dietary lysine is not needed for some fish species such as channel catfish. However, it has generally been observed that high levels of CSM adversely affected growth and hematological parameters, and caused histopathological changes in some fish species, due mainly to the toxicity of free gossypol. Earlier studies have also suggested that CSM contains compounds that may be beneficial in improving immune response and disease resistance in fish. Free gossypol, when present at high levels in the diet, is toxic to fish. The susceptibility of fish to dietary gossypol levels varies among species and parameters evaluated. Growth performance of rainbow trout was not affected at dietary free gossypol levels below 290 mg/kg but histological changes in livers and kidneys were observed at 95 mg/kg. Tilapia can tolerate relatively high levels of dietary gossypol. Dietary free gossypol from gossypol-acetic acid at levels up to 1,600 and 1,800mg/ kg had no effect on growth performance of Nile and blue tilapia, respectively. Information on the effect of dietary free gossypol on growth performance of channel catfish is not consistent. Concentrations of dietary free gossypol that adversely affected catfish performance range as low as 300 mg/kg to higher than 900 mg/kg. Recent findings suggested that free gossypol supplemented to practical diets is less toxic to channel catfish than that supplemented to purified diets. Total gossypol accumulation in tissues is directly correlated to dietary free gossypol concentrations. Free gossypol has been suggested as a compound in CSM responsible for improving the resistance of catfish to E. ictaluri infection. Recent studies, however, indicated that this compound is of little or no benefit in improving the resistance of catfish against E. ictaluri because the levels observed to enhance some immune parameters and post-challenge survival were much higher than those reported to be toxic to catfish. Gossypol has also been reported to inhibit spermatogenesis and cause serenity in males of some terrestrial animals. However, results of studies on the effect of dietary gossypol on reproductive performance of fish are not consistent among fish species.