J.D. Reed A. Woodward 1997 <p>We described the effects of two East African browses, <i>Acacia brevispica</i> and <i>Sesbania sesban</i>, on nitrogen metabolism of sheep and goats. The <i>A. brevispica</i> had a substantial amount of proanthocyanidins (condensed tannins); <i>S. sesban</i> did not. The browses were fed at three levels in combination with vetch (<i>Vicia dasycarpa</i>) and teff straw (<i>Eragrostis abyssinica</i>). Fecal N, N balance, and plasma urea N (PUN) were estimated with intact animals. Ruminal ammonia (RuA) and VFA concentrations were estimated with ruminally fistulated animals. Urinary N loss, PUN, RuA, and VFA concentrations were higher for S. sesban diets than for A. brevispica diets. Fecal N was highest with diets including A. brevispica due to high levels of fecal neutral-detergent insoluble N. Nitrogen retention was highest for diets including S. sesban. Nitrogen retention was adequate for A. brevispica diets because low urinary N compensated for high fecal N. Four hypotheses describe possible effects of tannins on N metabolism: 1) escape of protein from the rumen to the lower tract; 2) increased microbial yield; 3) increase in N-containing endogenous products; and 4) protein made indigestible in tannin-protein complexes. The effect of tannins in A. brevispica on N metabolism can best be described by the formation of indigestible tannin-protein complexes, although increased production of endogenous products is also possible.</p> application/pdf 10.2527/1997.7541130x en Acsess Nitrogen metabolism of sheep and goats consuming Acacia brevispica and Sesbania sesban article