ARS | Publication request: NO APPARENT DIFFERENCES IN INTESTINAL HISTOLOGY OF CHANNEL CATFISH (ICTALURUS PUNCTATUS) FED HEAT-TREATED AND NON-HEAT-TREATED RAW SOYBEAN MEAL

Submitted to: Aquaculture Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2004
Publication Date: April 4, 2005
Citation: Evans, J.J., Pasnik, D.J., Peres, H., Lim, C.E., Klesius, P.H. 2005. No apparent differences in intestinal histology of channel catfish (Ictalurus punctatus) fed heat-treated and non-heat-treated raw soybean meal. Aquaculture Nutrition. 11;123-129.

Interpretive Summary: Considerable effort has been placed on developing alternative protein sources for aquaculture diets to replace fish meal. Soybean meal (SBM) is a commonly utilized plant protein in fish feeds, because it is inexpensive, available, palatable, and has high nutritional value. However, inclusion of high levels of SBM in fish diets has led to adverse effects, such as reduced growth rates, reduced feed utilization efficiency, and cellular (histologic) alterations in the intestines. Many of these effects have been attributed to diet components that are treated with heating the feed. Little research has been undertaken to examine the effects of SBM on channel catfish (Ictalurus punctatus), so this study endeavored to determine the histologic effects of feeding heat-treated soybean meal to fingerling channel catfish. Fish were fed one of six diets: a diet containing 45% commercial soybean meal (CSBM), or diets with the CSBM replaced by non-heat-treated raw soybean meal (RSBM), or RSBM heated at 130 °C for 5, 10, 20, and 40 minutes. 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 cellular changes were found in the gastric glands, pancreas, and liver of fish in all the groups. Liver glycogen deposition was also observed in all the groups, and the spleen samples exhibited considerable brown-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 intestines. These findings suggest that RSBM could be utilized in channel catfish feed without causing severe histologic changes routinely associated with SBM utilization in fish.

Technical Abstract: 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 45% commercial soybean meal (CSBM), or diets with the CSBM replaced by non-heat-treated raw soybean meal (RSBM0), or RSBM heated at 130 °C for 5 (RSBM5), 10 (RSBM10), 20 (RSBM20), and 40 (RSBM40) min. 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 brown-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 intestines. These findings suggest that 45% RSBM could be utilized in channel catfish feed without causing severe histologic changes routinely associated with SBM utilization in fish.