The potential benefits of mixing leaves containing high and low levels of condensed tannin (CT) on N utilisation in sheep was studied at the Centro Internacional de Agricultura Tropical (CIAT), Colombia.

Supplements of Cratylia argentea (Ca) (tannin free), replaced with 0, 25, 50 or 100% Flemingia macrophylla (Fm) (25.1 g CT/kg DM) were fed as 40% of total ration DM (85g/M0·75), the remainder coming from Brachiaria dictyoneura (Bd). Treatments were offered in a replicated 4x4 latin square to eight male African Hair sheep (mean liveweight 23 (s.e. 1.5) kg), fistulated at the rumen and proximal duodenum (T-piece). Total collections of urine and faeces were used to estimate apparent N retention. Ammonia concentration was measured in rumen liquor samples taken hourly over 24 hours, while duodenal flows were estimated from spot samples using Ytterbium chloride as a single phase marker.