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 . 2 1 .4) and a-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; a-amylase activity was inhibited at intermediate tannin levels but was restored at the highest level. Dipeptidase (EC 3.4.13.11) and sucrose a-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.Tannin : Pancreatic enzymes : Brush border enzymes : Cockerel It is well established that tannins are potential protein precipitants (Hagerman & Butler, 1980;Hagerman & Klucher, 1986; Makker et al. 1987) and that they reduce the digestibilities of proteins (Mohammed & Ahnied, 1987) when present in animal feeds. Elevated faecal nitrogen excretion associated with ingestion of tannin-containing feeds is ascribed largely to interactions between either tannins and dietary protein or tannins and digestive enzymes, or both. However, Mitjavilla et al. (1977) concluded that the excess faecal N is mostly a result of mucus hypersecretion.Studies in vitro (Griffiths, 1981 ;Lumen & Salamat, 1980;Horigome et al. 1988) and in vivo (Griffiths & Moseley, 1980; Horigome er al. 1988) have demonstrated the formation of tannin-enzyme complexes. However, adopting a technique in vitro more relevant to the situation in vivo, Mole & Waterman (1987) showed that trypsin retained all its activity in the presence of tannic acid when the system included a substrate protein (bovine serum albumin ; BSA) and glycocholic acid, indicating that under such conditions tannins have a preferential affinity for dietary protein over enzyme protein. In previous work Mole & Waterman (1985) had shown that the formation of complexes between tannins and BSA, used as a substrate for proteolysis, could result in either enhancement or inhibition of proteolysis, or no effect at all depending on the tannin:BSA ratio in the complex.In contrast to what had been reported with rats (Griffiths & Moseley, 1980; Horigome et ul. 1988), tannins were shown to exert no effect on protein digestion by insect herbivores (Martin et ul. 1985(Martin et ul. , 1987 in terms of changes in activities of enzymes in the lumen of the small intestine, in order to provide further insight into the mode of action of dietary tannins. A further aim was to examine the effect of dietary tannins on the activity of membrane-bound enzymes wh...

1. A study was undertaken to investigate the susceptibility to peptic digestion of exogenous xylanase (EC 3.2.1.8) from Trichoderma longibrachiatum, added to a rye-based diet for broiler chickens, in order to elucidate its possible site of action. 2. It was also designed to investigate the effects of the enzyme (plus exogenous protease EC 3.4-24.28) when added to a rye-containing diet (60% rye/kg diet) on crypt cell proliferation in the mucosa of the small intestine, on short chain fatty acid (SCFA) concentrations in the small intestine digesta and in portal blood and on nutrient digestibilities. 3. In Experiment 1, the enzymes were added at activities 10x and 30x those recommended in commercial practice, but in Experiment 2 the activities were the recommended levels. 4. A significant proportion (estimated to be 15 to 20%) of the xylanase added at the higher concentration (15,000 and 45,000 units/kg diet) remained active in the small intestine of the growing chicken. 5. The crypt cell proliferation rate in birds fed on the control diet (45 cells/2 h) was significantly higher than in birds fed on the diets supplemented with enzyme at the higher level (29 and 33 cells/ 2 h), but there was no significant effect on SCFA. In birds fed on the diet supplemented with enzyme at the commercial level there was no clear-cut effect on crypt cell proliferation but exogenous xylanase could be detected in the small intestine. Intestinal fluid viscosity was reduced and growth performance of the birds was improved by the supplementation with exogenous enzymes. 6. Part of the improvement in growth performance could be ascribed to a 25% increase in the digestibility of nitrogen and a doubling of the digestibility of fat.

A BSTRA CTThe effects of heat treatments, namely microwave, infrared, hot air oven, autoclaving and cooking in boiling water, on trypsin inhibitor and haemagglutinating activities, tannin and phytate contents, essential amino acid composition and quality of proteins in winged bean, were investigated. The infrared, autoclaving and boiling-water treatments destroyed most of the trypsin inhibitor and haemagglutinating activities, and reduced the level of tannins. However, the microwave and oven heat treatments had no effect on these constituents of winged bean meal. Lysine and valine contents in the meals from infrared, autoclaving and cooking in boiling water treatments were lower than in untreated meal. There was a significant loss of threonine and arginine due to cooking of beans in boiling water. None of the treatments had any effect on phytate content.Rats fed on untreated, microwave-treated and oven-heated meal diets had low dry-matter intakes and lost weight significantly. However, remarkable improvements in dry-matter intake and weight gain were recorded for the diets containing meal from infrared, autoclaving and boiling-water treatments. The digestibility of proteins in the meal improved from 50 to 84% as a result of infrared and boiling-water treatments, whereas a noticeable decrease in protein digestibility was observed in ovenheated meals. There was a significant improvement in biological values and net protein utilisation values for the diets containing meals from infrared, autoclaving and boiling-water treatments over those of a diet having untreated meal.

Changes in the concentrations of glucosinolates from rapeseed meal and some glucosinolate degradation products during incubation in vitro with myrosinase (EC 3.2.3. l), with pepsin (EC 3.4.23.1)-HCI, and with contents of porcine small intestine and caecum were studied. When rapeseed meal was incubated with myrosinase, 5-vinyl oxazolidinethione (OZT) and butenyl and pentenyl isothiocyanates were produced; OZT concentration rose to a plateau after about 2 h. However, when incubated with caecal contents only OZT could be detected; its concentration peaked after about 4-5 h then declined. Under

No abstract