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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Harmeyer, J & Martens, H (1980) Aspects of urea metabolism in ruminants with reference to the goat. Journal of Dairy Science 63, 1707–1728.
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.
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.
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.
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.
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.
Jackson, AA (1995) Salvage of urea-nitrogen and protein requirements. Proceedings of the Nutrition Society 54, 535–547.
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.
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.
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.
Kennedy, PM & Milligan, LP (1978) Transfer of urea from the blood to the rumen of sheep. British Journal of Nutrition 40, 149–154.
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.
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.
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.
Marsh, WH, Fingerhut, B & Miller, H (1965) Automated and manual direct methods for the determination of blood urea. Clinical Chemistry 2, 624–627.
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.
Nolan, JV & Leng, RA (1972) Dynamic aspects of ammonia and urea metabolism in sheep. British Journal of Nutrition 27, 177–194.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.