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Urea recycling in sheep: effects of intake

Published online by Cambridge University Press:  09 March 2007

A. Sarraseca ,
E. Milne ,
M. J. Metcalf  and
G. E. Lobley
A. Sarraseca
Affiliation:
1Department of Agriculture, University of Aberdeen, Aberdeen, AB24 5UA, UK
E. Milne
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB21 9SB, UK
M. J. Metcalf
Affiliation:
BioSS, Rowett Research Institute, Bucksburn, Aberdeen, AB21 9SB, UK
G. E. Lobley*
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB21 9SB, UK
*
†Corresponding author:Dr G. E. Lobley, fax +44 (0)1224 716629, email [email protected]
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Abstract

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The effect of intake on urea production, entry into the digestive tract and return of N to the ornithine cycle was studied in four sheep. Each sheep received 0–6, 1–2 and 1.8 × estimated maintenance energy intake quantities of grass pellets for 9 d. After 4 d of adjustment, N balance measurements were conducted between days 5 and 8. From day 7 to day 9 animals were continuously infused, via the jugular vein, with [15N15N]urea and three urine samples were collected at approximately 2h intervals 48–54h after the start of infusion. Total urea and enrichments of [15N15N]- and [14N15N]urea in the urine samples were determined. Urea production was calculated from the isotopic dilution of [15N15N]urea and entry into the gastrointestinal tract (GIT) obtained from the difference between this and urinary urea elimination. Urea which enters the GIT undergoes hydrolysis to liberate NH3 which may be reabsorbed and enter the ornithine cycle, in which case the product is [14N15N]urea, based on the probabilities of labelled and unlabelled N providing ureagenic precursors. The quantity of urea-N which returns to the ornithine cycle from the GIT can thus be calculated. Existing models based on this approach yield overestimates of the fate of individual urea molecules due to a failure to allow for multiple recycling of [14N15N]urea species through the GIT. Refinements introduced to cover this resulted in a 33–48 % reduction in calculated return of label for the current study. The present model also predicted that 95 % of the label movements across the GIT could be accommodated by three or fewer entries and returns of urea-N and 99 % by recycling for a maximum of six occasions. Urea-N production increased with intake (P < 0.001) and exceeded digestible N values at all intakes. Urea which entered the digestive tract, both in absolute terms (P < 0.001) and as a proportion of production (0.62, 0.69, 0.73; P = 0.027), increased with intake. The proportion of entry into the digestive tract which was returned to the ornithine cycle remained reasonably constant (0.37–0.41) across all intakes but the absolute amount increased (5.6, 9.2 and 15.0gN/d; P < 0.001) with intake. If allowance is included for losses of 15N in faeces then the approach offers a relatively simple means of estimating anabolic reuse of urea by digestive tract micro-organisms and can complement data obtained from the technically more demanding arterio-venous and multiple-isotope techniques used hitherto.

Urea: Gastrointestinal tract: [15N]kinetics: Sheep

Keywords

UreaGastrointestinal tract[15N]kineticsSheep
Type
Animal Nutrition
Information
British Journal of Nutrition , Volume 79 , Issue 1 , January 1998 , pp. 79 - 88
Copyright
Copyright © The Nutrition Society 1998

References

Amos, HE, Evans, J & Burdick, D (1976) Abomasal protein recovery and microbial protein synthesis in wethers fed high and low quality forage diets. Journal of Animal Science 42, 970–976.CrossRefGoogle ScholarPubMed
Brosnan, JT, Brosnan, ME, Charron, R & Nissim, I (1996) A mass isotopomer study of urea and glutamine synthesis from 15N-labelled ammonia in the perfused rat liver. Journal of Biological Chemistry 271, 16199–16207.CrossRefGoogle Scholar
Bunting, LD, Boling, JA, MacKown, CT & Muntifering, RB (1987) Effect of dietary protein level on nitrogen metabolism in lambs: studies using 15N-nitrogen. Journal of Animal Science 64, 855–867.CrossRefGoogle ScholarPubMed
Calder, AG & Smith, A (1988) Stable isotope ratio analysis of leucine and ketoisocaproic acid in blood plasma by gas chromatography/mass spectrometry. Rapid Communications in Mass Spectrometry 2, 14–16.CrossRefGoogle ScholarPubMed
Cheng, KJ, McCowan, RP & Costerton, JW (1979) Adherent epithelial bacteria in ruminants and their roles in digestive tract function. American Journal of Clinical Nutrition 21, 139–148.CrossRefGoogle Scholar
Cheng, KJ & Wallace, RH (1979) The mechanism of passage of endogenous urea through the rumen wall and the role of ureolytic epithelial bacteria in the urea flux. British Journal of Nutrition 42, 553–557.CrossRefGoogle Scholar
Cooper, AJL, Nieves, E, Coleman, AE, Filc-De, Ricco S & Gelbard, AS (1987) Short term metabolic fate of [13N] ammonia in rat liver in vivo. Journal of Biological Chemistry 262, 1073–1080.CrossRefGoogle ScholarPubMed
Egan, AR, Boda, K & Varady, J (1986) Regulation of nitrogen metabolism and recycling. In Control of Digestion and Metabolism in Ruminants, pp. 386–402 [Milligan,, LP, Grovum, WL, and Dobson, A, editors]. Englewood Cliffs, NJ: Prentice-Hall.Google Scholar
El-Khoury, AE, Ajami, AM, Fukagawa, NK, Chapman, TE & Young, VR (1996) Diurnal pattern of the interrelationships among leucine oxidation, urea production and hydrolysis in humans. American Journal of Clinical Physiology 271, E563–E573.Google ScholarPubMed
Engelhardt, WV, Hinderer, S & Wipper, E (1978) Factors affecting the endogenous urea N secretion and utilization in the gastrointestinal tract. In Ruminant Digestion and Feed Evaluation, pp. 4.1–4.12 [Osbourn,, DF, Beever, DE, Thomson, DJ, editors]. London: Agricultural Research Council.Google Scholar
Harmeyer, J & Martens, H (1980) Aspects of urea metabolism in ruminants with reference to the goat. Journal of Dairy Science 63, 1707–1728.CrossRefGoogle Scholar
Harris, PM, Lobley, GE, Skene, PA, Buchan, V, Calder, AG, Anderson, SE & Connell, A (1992) Effect of food intake on hindlimb and whole-body protein metabolism in young growing sheep: chronic studies based on arterio-venous techniques. British Journal of Nutrition 68, 388–407.CrossRefGoogle ScholarPubMed
Havassey, I, Boda, K, Rybosova, E & Kuchar, S (1973) Increased urea transport from muscle tissue to blood in fasting sheep. Physiologica Bohemoslovakia 22, 261–265.Google Scholar
Hauck, RD (1982) Nitrogen-isotope-ratio analysis. In Methods of Soil Analysis, Part 2, pp. 735–779 [Page, AL, editor]. Madison, WI: American Society of Agronomy Inc.Google Scholar
Houpt, TR (1970) Transfer of urea and NH3 to the rumen. In Physiology of Digestion and Metabolism in the Ruminant, pp. 119–131. Newcastle upon Tyne: Oriel Press.Google Scholar
Huntington, GB (1989) Hepatic urea synthesis and site and rate of urea removal from blood of beef steers fed alfalfa hay or a high concentrate diet. Canadian Journal of Animal Science 69, 215–223.CrossRefGoogle Scholar
Jackson, AA (1995) Salvage of urea-nitrogen and protein requirements. Proceedings of the Nutrition Society 54, 535–547.CrossRefGoogle ScholarPubMed
Jackson, AA, Danielsen, MS & Boyes, S (1993) A non-invasive method for measuring urea kinetics with a single dose of 15N15N-urea in free-living humans. Journal of Nutrition 123, 2129–2136.Google Scholar
Jackson, AA, Picou, D & Landman, JP (1984) The non-invasive measurement of urea kinetics in normal man by a constant infusion of 15N15N-urea. Clinical Nutrition 38C, 339–354.Google Scholar
Jackson, AA & Wootton, SA (1990) The energy requirements for growth and catch-up growth. In Activity Energy Expenditure and Energy Requirements of Infants and Children, pp. 185–214 [Schurch, B and Scrimshaw, NS, editors]. Switzerland: International Dietary Energy Consultative Group.Google Scholar
Kennedy, PM & Milligan, LP (1978) Transfer of urea from the blood to the rumen of sheep. British Journal of Nutrition 40, 149–154.CrossRefGoogle Scholar
Kennedy, PM & Milligan, LP (1980) The degradation and utilization of endogenous urea in the gastrointestinal tract of ruminants: a review. Canadian Journal of Animal Science 60, 205–221.CrossRefGoogle Scholar
Lobley, GE, Connell, A, Lomax, MA, Brown, DS, Milne, E, Calder, AG & Farningham, DAH (1995) Hepatic detoxification of ammonia in the ovine liver: possible consequences for amino acid catabolism. British Journal of Nutrition 73, 667–685.CrossRefGoogle ScholarPubMed
Lobley, GE, Weijs, PJM, Connell, A, Calder, AG, Brown, DS & Milne, E (1996) The fate of absorbed and exogenous NH3 as influenced by forage or forage-concentrate diets in growing sheep. British Journal of Nutrition 76, 231–248.CrossRefGoogle ScholarPubMed
Marsh, WH, Fingerhut, B & Miller, H (1965) Automated and manual direct methods for the determination of blood urea. Clinical Chemistry 2, 624–627.CrossRefGoogle Scholar
Meakins, TS & Jackson, AA (1996) Salvage of exogenous urea nitrogen enhances nitrogen balance in normal men consuming marginally inadequate protein diets. Clinical Science 90, 215–255.CrossRefGoogle ScholarPubMed
Nolan, JV & Leng, RA (1972) Dynamic aspects of ammonia and urea metabolism in sheep. British Journal of Nutrition 27, 177–194.CrossRefGoogle ScholarPubMed
Reynolds, CK, Tyrrell, HF & Reynolds, PJ (1991) Effects of diet forage-to-concentrate ratio and intake on energy metabolism in growing beef heifers: net nutrient metabolism by visceral tissues. Journal of Nutrition 121, 1004–1015.CrossRefGoogle ScholarPubMed
Schestakow, P (1905) Über die Einwirkung von unterclorigsauren Salzen auf Harnstoff und eine neue Hydrazinsynthese (On the action of hypochlorous acid salts on urea and a new synthesis of hydrazine). Chemisches Zentralblatt 1, 1227–1228.Google Scholar
Siddons, RC, Nolan, JV, Beever, DE & MacRae, JC (1985) Nitrogen digestion and metabolism in sheep consuming diets containing contrasting forms and levels of N. British Journal of Nutrition 54, 175–187.CrossRefGoogle ScholarPubMed
Torrallardona, D, Harris, CI, Coates, ME & Fuller, MF (1996) Microbial amino acid synthesis and utilization in rats. 1. Incorporation of 15N from 15NH4Cl into lysine in the tissues of germ-free and conventional rats. British Journal of Nutrition 76, 689–700.CrossRefGoogle Scholar
Torrallardona, D, Harris, CI, Milne, E & Fuller, MF (1994) The contribution of intestinal microflora to amino acid requirements in pigs. In Proceedings of VIth International Symposium on Digestive Physiology in Pigs. European Association of Animal Production Publication no. 80, pp. 245–248 [Souffrant, WB and Hagemeister, H, editors]. Dummerstorf: Forschungsinstitut fur die Biologie landwirtschaftlicher Nutztiere.Google Scholar
Walser, M (1968) Use of isotopic urea to study the distribution and degradation of urea in man. In Urea and Kidney, pp. 421–429 [Schmidt-Nielson, B, editor]. Amsterdam: Excerpta Medica Foundation.Google Scholar
Walser, M, George, J & Bondelos, LJ (1954) Altered proportions of isotopes of molecular nitrogen as evidence for a monomolecular reaction. Journal of Chemical Physiology 22, 1146.CrossRefGoogle Scholar
Whitelaw, FG & Milne, JS (1991) Urea degradation in sheep nourished by intragastric infusion: effects of level and nature of energy inputs. Experimental Physiology 76, 77–90.CrossRefGoogle ScholarPubMed
Whitelaw, FG, Milne, JS, Ørskov, ER, Stansfield, R & Franklin, MF (1990) Urea metabolism in sheep given conventional feeds or nourished by intragastric infusion. Experimental Physiology 75, 239–254.CrossRefGoogle ScholarPubMed
Wolfe, RR (1981) Measurement of urea kinetics in vivo by means of a constant tracer infusion of di-15N-urea. American Journal of Physiology 240, E428–E434.Google ScholarPubMed