Forage intake and nitrogen utilization by sheep as affected by condensed tannins

Three trials were conducted to determine the effects of condensed tannins (CT) of Desmodium ovalifolium Wallich ex Gagnep cv. CIAT 350 on forage intake and N utilization by sheep. Polyethylene glycol (PEG) was used as CT binding agent. In Trial 1, 12 growing sheep were assigned to one of four treatments: Centrosema macrocarpum Bentham, C. macrocarpum plus PEG (5% DM), D. ovalifolium, D. ovalifolium plus PEG (5% DM). Soluble CT were.17 and 4.6% for C. macrocarpum and D. ovalifolium, respectively. Dry matter intake was higher (P $\u3c$.10) in D. ovalifolium with PEG (23 g DM.kg$\sp{-1}$ BW.d$\sp{-1})$ than in D. ovalifolium (19 g DM.kg$\sp{-1}$ BW.d$\sp{-1}).$ Nitrogen retained for D. ovalifolium (1.3 g/d) was lower (P =.078) than D. ovalifolium plus PEG (4.3 g/d). In trial 2, three ruminally and duodenally fistulated sheep were used in a 3 x 3 latin square. Treatments were D. ovalifolium (CONTROL, 4.1%), D. ovalifolium plus PEG (3.5%, DM) and D. ovalifolium plus PEG (7.0%, DM). Intake was restricted (50 g DM/kgBW$\sp{.75}).$ Reduction of soluble CT intake reduced (r =.82, $P = .0061$) flow of non ammonia N to duodenum. Fecal N excretion was lower (P =.023) for the PEG diets and was correlated to intake of soluble CT (r =.86, $P\u3c.001).$ CONTROL diet had highest N apparent absorption $(P = .0119).$ In trial 3, three sheep, fistulated at the rumen, duodenum and ileum, were arranged in an 2 x 3 row column design. Treatments were D. ovalifolium (CONTROL) and D. ovalifolium plus PEG (5% DM). The PEG reduced soluble CT from 4.6% to 1.8%. N flux to duodenum was higher (P $\u3c$.01) for the CONTROL (8.3 g N/d) than in the PEG (5.9 g N/d) diets. Sheep fed CONTROL diets had higher $(P = .056)$ N absorption (3.8 g/d) than those fed PEG diet (3.0 g/d). Soluble CT reduced protein degradation in the rumen increasing flow of N to small intestine but did not affect protein digestion or absorption in the small intestine. However, CT reduced DM intake and therefore, energy and N intake