The effect of trypsin inhibitors on pancreatopeptidase E, trypsin, chymotrypsin and amylase in the pancreas and intestinal tract of chicks receiving raw and heated soya-bean diets

1. Feeding on a raw soya-bean diet (RSD) increased the levels of trypsin, chymotrypsin and pancreatopeptidase E but decreased the level of amylase in the pancreas of chicks as compared to a heated soya-bean diet (HSD), while supplementation of HSD with soya-bean trypsin inhibitors increased the activity of all four enzymes. HSD + trypsin inhibitors caused significant enlargement of the pancreas but only a slight depression in growth rate. 2. Fasting for 24 h of chicks previously given RSD and HSD increased the activity of all four enzymes but the increase was much greater in chicks previously given RSD than in those previously given HSD. 3. Feeding RSD for 4 d to chicks previously adapted to HSD resulted in a dramatic inhibition in growth rate, a small increase in pancreas weight, and an increase in the activity of all proteolytic enzymes, while no change in the amylase was detectable. 4. Trypsin, chymotrypsin and pancreatopeptidase E activities were assayed in the contents of the small intestine and caecum of chicks fed on RSD or HSD over a period of 35 d. Trypsin and chymotrypsin activities in the small intestine were lower in chicks fed on RSD while pancreatopeptidase E activity was almost equal or even higher in RSD-fed chicks, especially at the age of 35 d. Trypsin activity in the caecum of RSD-fed chicks was lower at all stages of the experiment, while the pancreatopeptidase E and chymotrypsin activities in the caecum of RSD-fed chicks exceeded the levels in the HSD group at the age of 21 and 35 d respectively. It would appear therefore that pancreatopeptidase E may play an important part in overcoming the inhibition of the proteolytic activity in the intestine of chicks fed on RSD.