Accentuated response to soybean inhibitors by meal-feeding in various species

Diets containing raw soybean products (RSD) fed ad libitum caused a reduction in food consumption and growth, pancreatic enlargement, hypersecretion of digestive enzymes, and enlargement of intestinal segments and their contents in rats, chicks and geese. These effects were found to be related to the concentration of trypsin inhibitor (TI) in the diet. Geese were more sensitive than rats and chicks. Calves fed RSD did not respond in pancreatic hypertrophy and hypersecretion of digestive enzymes, but growth was depressed. Meal-feeding also caused enlargement of the pancreas, digestive tract segments and their contents. The effects of feeding RSD and of meal feeding were found to be additive. In ad libitum feeding the animal can regulate food consumption and moderate the effects of antinutritional factors in the diet. Meal or tube-feeding interfered with this defense mechanism and the negative effects of RSD were accentuated and were lethal in non adapted rats and geese. In long-term studies the incidence of pancreatic nodules was correlated to the level of TI in the diet. Feeding RSD potentiated the carcinogenic effect of azaserine and meal feeding enhanced the incidence and size of the pancreatic nodules in rats fed RSD.