Optimizing Soybean Meal Levels in Alternative Diets for Pond-Raised Hybrid Catfish

We evaluated decreasing soybean meal levels by the use of a combination of cottonseed meal and corn germ meal for pond-raised hybrid catfish (Channel Catfish Ictalurus punctatusxBlue Catfish I. furcatus). Five 28% protein diets containing 40, 30, 25, 20, 15% of soybean meal were formulated based on digestible nutrients and energy to meet or exceed all known nutrient requirements of Channel Catfish. Fingerling hybrid catfish with a mean initial weight of 25.1g/fish were stocked into 25, earthen ponds (0.04 ha) at a rate of 14,826 fish/ha. Fish were fed once daily to apparent satiation over a 184-d growing season. Reducing soybean meal levels from 40% to 15% in the diet by the use of a combination of cottonseed meal and corn germ meal did not significantly affect total amount of diet fed, gross yield, weight gain, and survival of hybrid catfish by ANOVA or regression analyses. However, feed conversion ratio was significantly higher in fish fed diets containing 30% soybean meal than those fed the control diet (40% soybean meal) and feed conversion ratio increased linearly as soybean meal levels decreased. Hybrid catfish fed diets containing 20% and 15% soybean meal had significantly lower carcass yield than fish fed the control diet. Fish fed the diet containing 15% soybean meal also had significantly lower fillet yield. Regression analyses show that both carcass and fillet yields decreased linearly with decreasing soybean meal levels in the diet. No significant differences were observed for fillet protein, fat, and moisture levels among fish fed the diets containing various levels of soybean meal. A 28% protein diet containing 25% soybean meal appears to support maximum growth of hybrid catfish without marked impact on feed conversion ratio and processed yield. Received August 1, 2013; accepted October 7, 2013