No apparent differences in intestinal histology of channel catfish (Ictalurus punctatus) fed heat-treated and non-heat-treated raw soybean meal

The histopathologic effects of feeding heat-treated soybean meal to fingerling channel catfish (Ictalurus punctatus) were studied. Fish were fed one of six diets: a diet containing 450 g kg(-1) commercial soybean meal (CSBM), or diets with the CSBM replaced by non-heat-treated raw soybean meal (RSBM0), or RSBM heated at 130 degrees C for 5 min (RSBM5), 10 min (RSBM10), 20 min (RSBM20) or 40 min (RSBM40). After 10 weeks, tissue samples were taken from the stomach, proximal intestine, distal intestine, liver, pancreas and spleen from fish in each group for histologic examination. Mild necrotic lesions were found in the gastric glands, pancreas and liver of fish in all the groups (treatment and control groups). Hepatic glycogen deposition was also observed in all the groups, and the spleen samples exhibited considerable brownish-black pigment deposition around the splenic corpuscles and diffuse mild-to-moderate congestion in all of the groups. Generally, these histologic effects appeared to be equivocal between all of the groups, and no abnormalities were noted in the proximal or distal intestine. These findings suggest that feeding channel catfish a diet containing 450 g kg(-1) non-heat-treated RSBM did not cause severe histologic changes associated with soybean meal anti-nutritional factors as have been reported in salmonids.