Response of young chicks to raw, defatted, Kunitz trypsin inhibitor variant soybeans as sources of dietary protein.

Two trials, using 264 8-day-old male crossbred chicks, were conducted to evaluate the nutritional value of two trypsin-inhibitor (Kunitz) variant soybeans. These two variants, designated PI 157440 (PI) and number 661, have lower trypsin-inhibitor activities than do US commercially grown soybean cultivars such as Amsoy 71. Raw PI, 661, and Amsoy 71 soybeans were defatted and then compared to a commercially processed solvent extracted soybean meal (SBM) using purified diets with soybeans or SBM as the sole source of protein. Trials 1 and 2, respectively, were of 6 and 7 days duration. SBM was superior to each of the raw meals. In Trial 1, gain/feed was higher from PI than from Amsoy 71. In Trial 2, gain and gain/feed were higher (P < .05) from PI and 661 than from Amsoy 71. Pancreas weight as a percent of body weight reflected the trypsin-inhibitor intake. The addition of .3% DL-methionine to each diet improved (P < .05) gain and gain/feed. In Trial 2 gain and gain/feed from PI plus methionine was greater (P < .05) than from 661 plus methionine. In both trials, raw PI plus 3% methionine produced gain and gain/feed comparable to SBM without added methionine.