Comparative effects of feeding and duodenal infusion of monensin on digestion in sheep

Abstract

The effect of monensin on digestion was compared when it was used as feed additive or infused into the duodenum. Six Texel wethers fitted with ruminal, simple duodenal and re-entrant ileal cannulae, divided into three groups, were fed a mixed diet alone (control) or with 33 mg of monensin in feed or infused through the duodenal cannula. The experiment was designed as a 3 × 3 Latin square. Feeding monensin increased (P < 0.05) the amount of OM digested in the rumen and small intestine; infusion into the duodenum had no effect on this parameter. Monensin had no effect on the extent or site of N digestion. No ruminal recycling of monensin was observed since ruminal VFAs were not altered by monensin infusion into the duodenum. VFAs in the hindgut were only modified when monensin was fed (improvement of propionate proportion, P < 0.05). Amylase activity remained unchanged in the intestine whatever the monensin supply. Only fed monensin increased (P < 0.05) trypsin activity. Infused monensin increased the plasma glucose level (P < 0.05), which indicates that monensin has metabolic effects. These results show that the intestine is not the major target for monensin when it is used as a growth promoter in ruminants. Key words: Monensin, intestinal digestion, plasma glucose, sheep, VFA, nigrogen