Preliminary evidence that cholesterol improves growth and feed intake of soybean meal-based diets in aquaria studies with juvenile channel catfish, Ictalurus punctatus

Two feeding trials were conducted in aquaria to examine the effects of dietary soybean meal (SBM), purified soybean saponin and supplemental cholesterol concentrations on growth responses of channel catfish. In the first experiment, five dietary treatments were formulated to contain either 0%, 13.9%, 27.7%, 41.6% or 55.5% SBM which was added to the diets at the expense of soy protein concentrate (SPC) on an isonitrogenous basis. Each diet was fed to apparent satiation twice daily to triplicate groups of fish initially weighing 7.0 g/fish. At the end of the 8-week feeding trial, weight gain and feed intake (FI) in fish fed diets containing 0% or 13.9% SBM were significantly higher than in fish fed diets containing 27.7%, 41.6% or 55.5% SBM. Fish fed 27.7% dietary SBM exhibited significantly higher weight gain and feed intake compared with fish fed 41.6% or 55.5% dietary SBM. No significant differences were detected in feed efficiency (FE) or survival among fish fed any of the dietary treatments. In the second experiment, five dietary treatments were formulated to contain various concentrations of SBM (0% and 55.5%), supplemental cholesterol (0% and 1.0%) and purified soybean saponin (0% and 0.26%) to determine whether cholesterol could alleviate the deleterious effects of high dietary SBM concentrations. Each diet was fed to apparent satiation twice daily to triplicate groups of channel catfish initially weighing 9.7 g/fish. At the end of the 8-week feeding trial, weight gain, FI and FE were not significantly different between fish fed the purified control diet and fish fed the SBM-based diet (55.5% SBM) supplemented with 1.0% cholesterol. Fish fed the SBM-based diet containing 1.0% supplemental cholesterol exhibited significantly higher growth rate and FI compared with fish fed the SBM-based diet containing no supplemental cholesterol. Weight gain and FI in fish fed the diets containing purified soybean saponin were not significantly different than in fish fed the purified control diet, indicating that soy saponin was not responsible for reduced feed consumption in fish fed high dietary SBM concentrations. Results of this research indicated that 1.0% supplemental cholesterol may improve growth responses in juvenile channel catfish fed SBM-based diets and that soybean saponin was not responsible for reduced FI in fish fed high dietary SBM concentrations.