HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Harmeyer, J. Articles by Martens, H. Search for Related Content PubMed PubMed Citation Articles by Harmeyer, J. Articles by Martens, H.

Aspects of Urea Metabolism in Ruminants with Reference to the Goat¹

Institute of Physiology, Veterinary School, Hannover, West Germany

ABSTRACT

In goats and other ruminants, urea functions as a source of nitrogen for protein biosynthesis in the digestive tract. Ammonia can be absorbed in the digestive system when formed in excessive quantities and enhance formation of urea, or it can be derived from urea of blood plasma when its formation from feed sources is small. Entry rates of urea into plasma may vary from 4 to 80 ;µmol/min per kg^.75 body weight depending on dietary conditions. Urea formation is related to nitrogen intake of which approximately 70% passes into the urea pool of plasma. Irreversible losses of urea of plasma into the digestive tract vary between 10 and 90% depending on the protein to energy ratios of the diet. Entry of urea from plasma into the rumen appears to be a passive process which is sensitive to short-term changes of urea concentrations in plasma. Permeability of ruminal epithelium to urea may be altered by fermentation products of rumen (ammonia, carbon dioxide, volatile fatty acids). The influx of nitrogen into the rumen is related to needs for nitrogen of microbial populations and is associated with changes of renal excretion and tubular reabsorption of urea. Combined gastrointestinal and renal responses exert a synergistic effect on improved utilization of urea of plasma when uptake of dietary nitrogen is limited in goats and other ruminants.

¹ Supported in part by grants from American Dairy Science Association, University of Delaware, National Research Council, and Agency for International Development. No.:DSAN-G-O110, Project No.:931-1155.11.

This article has been cited by other articles:

				D. Kiran and T. Mutsvangwa Effects of barley grain processing and dietary ruminally degradable protein on urea nitrogen recycling and nitrogen metabolism in growing lambs J Anim Sci, December 1, 2007; 85(12): 3391 - 3399. [Abstract] [Full Text] [PDF]

				N. E. Sunny, S. L. Owens, R. L. Baldwin VI, S. W. El-Kadi, R. A. Kohn, and B. J. Bequette Salvage of blood urea nitrogen in sheep is highly dependent on plasma urea concentration and the efficiency of capture within the digestive tract J Anim Sci, April 1, 2007; 85(4): 1006 - 1013. [Abstract] [Full Text] [PDF]

				D. W. Bohnert, C. S. Schauer, S. J. Falck, and T. DelCurto Influence of rumen protein degradability and supplementation frequency on steers consuming low-quality forage: II. Ruminal fermentation characteristics J Anim Sci, November 1, 2002; 80(11): 2978 - 2988. [Abstract] [Full Text] [PDF]