Replacement of soybean meal with roasted full-fat soybeans from high-protein or conventional cultivars in diets for broiler chickens

Abstract

The effects were examined of replacing part or all of the soybean meal in the starter and finisher diets for male broiler chickens with ground, roasted, full-fat soybeans from either a high-protein (AC Proteus) or conventional (Baron) cultivar. The starter (1–21 d) and finisher (22–36 d) diets were formulated by replacing, on an isonitrogenous basis, part or all of the soybean meal in the barley–wheat-based control diets with the roasted soybeans. Digestibility of dry matter, corrected nitrogen and energy were estimated by an index method for the last 2 d of the starter and grower periods. Soybean level influenced body weight gains directly in a quadratic manner, and feed intakes or feed conversions by inversely linear relationships (P < 0.05 and P < 0.01) during the starter period. Performance during the finisher period or during the entire growth period was not influenced (P > 0.05) by dietary soybean source. Dry matter and energy digestibilities at both 21 and 35 d, and nitrogen at 35 d were affected in a quadratic manner (P < 0.05 or P < 0.01) by the soybean level of the diets, whereas, a linear relationship was present for the apparent metabolizable energy (AME) content (P < 0.001). Soybean source had no effect on nutrient utilization, except for dry matter or energy digestibility during the starter period (P < 0.01). In conclusion, the optimal performance should be obtained when the ratio of roasted full-fat soybeans to soybean meal is about 2:1 in the starter feeds for broiler chickens. Key words: Full-fat soybeans, soybean meal, high-protein soybeans, broiler, growth, nutrient digestibilities