Submitted to: Fish Nutrition and Feeding Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/7/2002
Publication Date: 6/7/2002
Citation: Peres, H., Lim, C.E., Klesius, P.H. 2002. Nutritional value of heat-treated soybean meal for channel catfish (Ictalurus punctatus). Proceeding of Fish Nutrition and Feeding Symposium Proceedings. p. 190. Interpretive Summary: Soybean meal (SBM) is the major plant protein source used in channel catfish feeds and can comprise up to 50% in the diets. Raw SBM (RSBM) contains a number of anti-nutritional factors which must be heat-treated before it can be used in feeds for monogastric animals and fish. The effect of heat treatment on fish health is not known. This study was conducted to evaluate the effect of heating duration of RSBM (autoclaving using the dry cycle at 0, 5, 10, 20 and 40 min) on catfish performance, their immune responses and resistance to a bacterium, Edwardsiella ictaluri, challenge. Isoenergetic and isoproteinous diet containing commercial SBM served as the control. Results showed that fishy fed the diet containing RSBM autoclaved using the dry cycle at 130 C and 22 PSI for 40 min improved the growth performance, feed efficiency, whole body protein content and plasma protein and lysozyme activity to levels comparable to those obtained with commercial SBM diet. However, based on feed intake, protein dispersity index and protein digestibility, optimum heating time should be less than 40 min. Fish fed diets containing inadequately heat-treated RSBM exhibited increased number of white blood cells migrating in the presence of the bacteria protein, antibody against the bacteria and improved the resistance of fish against enteric septicemia of catfish. Based on this information, RSBM may contain heat-sensitive compounds or factors that improved the resistance of juvenile channel catfish against E. ictaluriinfection. More studies to identify these compounds and understand the mechanisms in which these compounds interact with fish immune functions and disease resistance will lead to improve heat treatment of RSBM, increase the use of SBM and reduce fish mortality due to diseases.
Technical Abstract: A study was undertaken to evaluate the effect of heat treatment of defatted raw soybean meal (RSBM) on the growth, hematology, immune response and resistance of channel catfish to Edwardsiella ictaluri. Six isocaloric and isonitrogenous practical diets were formulated. A diet containing 45% of commercial soybean meal (CSBM) served as the control. RSBM, unheated (RSBM0) and heated in an autoclave (dry cycle) at 130 deg.C and 22 psi for 5 (RSBM5), 10 (RSBM10), 20 (RSBM20), and 40 min (RSBM40), was used to isonitrogenously replace the CSBM in the control diet. Each diet was fed to juvenile catfish (4.98g) in triplicate aquaria twice daily to satiation for 10 weeks. Another batch of diets containing 1% of chromic oxide was used for digestibility trial. Heating RSBM for 20 min. or longer lowered trypsin inhibitor (TI) content and increased the apparent protein digestibility. The protein dispersibility index decreased with increasing heating duration. Fish fed CSBM and RSBM40 diets had similar weight gain, protein efficiency ratio and apparent protein utilization which were significantly higher than those of fish fed the other diets. Feed intake significantly increased when RSBM was heated for 20min or longer. Fish fed the CSBM diet had significantly lower feed intake but higher feed efficiency than those fed the CSBM diet. Whole-body protein was highest for fish fed the RSBM40 diet but did not differ from that of fish fed the CSBM diet. Hepatosomatic and visceral indices of fish fed CSBM and RSBM40 diets were significantly lower than those fed other diets. Total cell count, red blood cell count, hematocrit and hemoglobin were not affected by dietary treatments. Plasma lysozyme activity and protein of fish fed the RSBM40 diets were similar and significantly higher than those of fish fed the other diets. Cumulative mortality 14-day post challenge with E. ictaluri was significantly lower for fish fed the RSBM5 and RSBM10 diets but significantly increased when heating time was increased to 40 min. Macrophage chemotaxis in the presence of exoantigen and antibody titer against E. ictaluri was higher for the groups fed the RSBM containing diets than those fed the CSBM diet, although the differences were not always significant.