Diets containing vegetable tannins, predominantly hydrolysable gallotannins, at levels of 13.5, 25 and 50 g/kg were fed to growing broiler cockerels to examine their effect on enzymes in the pancreas, the intestinal lumen and the intestinal mucosa. Pancreas weight per unit live weight showed a significant (P < 0.05) increase with increasing level of dietary tannin while that of the liver remained unaffected. Trypsin (EC 3.4.21.4) and α-amylase (EC 3.2.1.1) activities in the pancreas of birds fed at the highest level of tannins were more than double those from birds fed on a tannin-free control diet. In the intestinal lumen inhibition of trypsin activity increased with increasing level of dietary tannin; α-amylase activity was inhibited at intermediate tannin levels but was restored at the highest level. Dipeptidase (EC 3.4.13.11) and sucrose α-glucosidase (disaccharidase) (EC 3.2.1.48) in the intestinal mucosa were both inhibited by tannins. Growth of the birds and digestibility of nitrogen were adversely affected by the tannin-containing diets.
