Relationships Between Color, Trypsin Inhibitor Contents, and Urease Index of Soybean Meal and Effects on Broiler Performance

Abstract

Three experiments were conducted to determine the relationships between trypsin inhibitor contents, urease index, and color of soybean meal, and the effect on broiler performance. Either 0, 8, 10, 12, 14, or 16% moisture (Experiment 1) or 0, 2, 4, 6, 8, or 10% moisture (Experiment 2) was added after dehydrating raw, flaked, solvent-extracted soybeans to 2% moisture. Each sample was then sealed in .473-liter jars, autoclaved for 0 to 135 min, with 15-min intervals, and dried at 37 C in a vacuum oven to remove all remaining moisture. In Experiment 3 commercial soybean meal with 12.12 μg trypsin inhibited/mg protein (μg/mg) was autoclaved for 0 to 25 min with 5-min intervals to determine the effect of additional heat on broiler performance and SBM color.Commercial soybean meal with 12.12 μg/mg trypsin inhibitor, tristimulus +a color value of 3.21, and a urease index of .19 Δ pH supported poorer growth and feed efficiency in broilers than the same soybean meal heated an additional 10 min and, thus, 1.77 μg/mg trypsin inhibitor, a + a color value of +4.76, and urease index of .02 Δ pH. Results indicated that color is a good predictor of trypsin inhibitor content and broiler performance. Additional heating resulted in higher +a color values and poorer broiler performance, indicating that color may also be used to determine overprocessing.Particle size of the soybean meal influenced the color. The soybean meal ground to pass a 20 mesh screen supported the best broiler performance when tristimulus color values ranged from +4.5–5.5 ±a color values or 58–65 L color values. These results confirm that color is a quick and reliable method of determining soybean meal quality.