The Effect of Heating Soybean Meal on the Apparent Digestibility and Metabolism of Protein, Methionine and Lysine by Cockerels

IT IS an established phenomenon (Liener, 1962) that raw soybean (RS) interferes with the normal growth of animals. Several reasons have been suggested for this growth depression, one of which is related to the depressed digestibility and, hence, lower utilization of the raw as compared to the heated soybean (HS) protein. However, Mitchell et al. (1945) found that the digestibility of RS is only slightly lower than that of the HS, while the biological value is much lower. Hayward et al. (1936), Evans et al. (1947) and Carroll et al. (1952) claimed that the growth differences found among animals fed HS and RS cannot be accounted for by the differences in digestibility of these products. On the other hand, there are several authors who attributed the lower growth rate of animals fed RS than of those fed HS to a relatively lower availability of the methionine in RS compared to…