title: Nitrogen metabolism of sheep and goats consuming Acacia brevispica and Sesbania sesban.
abstract: We described the effects of two East African browses, Acacia brevispica and Sesbania sesban, on nitrogen metabolism of sheep and goats. The A. brevispica had a substantial amount of proanthocyanidins (condensed tannins); S. sesban did not. The browses were fed at three levels in combination with vetch (Vicia dasycarpa) and teff straw (Eragrostis abyssinica). 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.
authors.affiliation: International Livestock Centre for Africa, Addis Ababa, Ethiopia. Andrea_Woodward@nbs.gov
authors.forename: A
authors.initials: A
authors.lastname: Woodward
authors.forename: J D
authors.initials: JD
authors.lastname: Reed
mesh_terms: D000045:Acacia / Q000737:chemistry; D000641:Ammonia / Q000032:analysis; D000704:Analysis of Variance; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000872:Anthocyanins / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D000975:Antioxidants / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D001806:Blood Urea Nitrogen; D004063:Digestion / Q000502:physiology; D004435:Eating / Q000502:physiology; D005002:Ethiopia; D005232:Fatty Acids, Volatile / Q000032:analysis / Q000378:metabolism; D005243:Feces / Q000737:chemistry; D006041:Goats / Q000378:metabolism* / Q000502:physiology; D008297:Male; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D044945:Proanthocyanidins; D012417:Rumen / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D012756:Sheep / Q000378:metabolism* / Q000502:physiology; D013634:Tannins / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D014197:Trees / Q000737:chemistry
chemical_list: D000872:Anthocyanins; D000975:Antioxidants; D005232:Fatty Acids, Volatile; D044945:Proanthocyanidins; D013634:Tannins; C013221:proanthocyanidin; D000641:Ammonia; D009584:Nitrogen