Abstract
Serveral experiments were conducted to study the effects of fractions isolated from unheated soybean meal on pancreatic hypertrophy, fat absorption, utilization of non-fat components of the diet, and growth rate of chicks, to determine whether these measurements were affected by specific components of the meal. Unheated soybean meal was fractionated into a water-insoluble residue, pH 4.4. insoluble proteins, salts insoluble at pH 8, and whey proteins recovered by dialysis and lyophilization of the portion of the meal soluble at pH 4.4. When fed to chicks at levels of 1.3 to 1.9% of the diet, the soybean whey proteins markedly depressed growth rate, caused pancreatic hypertrophy, reduced fat absorption, and lowered metabolizable energy value of the diet. Whey proteins were batch separated on DEAE cellulose into 2 fractions, one high in hemagglutinin activity and one high in trypsin inhibitor activity. Neither fraction when fed alone affected growth rate, fat absorption or metabolizable energy value of the diet to the same extent as a combination of the 2 fractions. A diet containing 0.6% of a crystalline Kunitz soybean trypsin inhibitor depressed growth rate of chicks and metabolizable energy value of the diet, caused pancreatic hypertrophy, but had no other undesirable effects. These experiments suggest that multiple factors are present in unheated soybean meal which cause the detrimental effects observed.