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

The effects were examined of replacing part or all of the soybean meal in t he starter and finisher diets for male broiler chickens with ground, roaste d, full-fat soybeans from either a high-protein (AC Proteus) or conventiona l (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 soy bean 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. Soy bean 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 a nd 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 relation ship 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 co nclusion, the optimal performance should be obtained when the ratio of roas ted full-fat soybeans to soybean meal is about 2:1 in the starter feeds for broiler chickens.