Effect of soya bean antinutritional proteins on rats and sheep

Abstract

In the first experiment we showed that isolated soya bean lectin (SBA) and trypsin inhibitor (STI) are unable to suppress food consumption in rats, if administered orally at a level of 100 mg/kg b.w. Other factors connected with raw soya bean may be responsible for suppression. In another experiment defatted raw soya bean flour was administered intraruminally at a level of 10 g/kg b.w. to a sheep fitted with ruminál, duodenal and ileal cannulas. Soya bean lectin (SBA) and trypsin inhibitors appeared in the duodenum within 1 hour; both reached the terminal ileum and had disappeared by the time 24 hours had elapsed. The passage of the lectin along the gut progressively lagged behind that of the inhibitors, which indicates that this lectin binds to the intestinal surface in this species. The inhibitors were neutralised by marked pancreatic hypersecretion resulting in a supraphysiological trypsin level in the intestine. This experiment shows that soya bean antinutritional proteins pass along the digestive tract at different rates, and if administered intraruminally they are not degraded effectively in the forestomachs. It is assumed that this differential passage may also occur in monogastric animals.