Agricultural and Food Research Council. 1992. Nutritive requirements of ruminant animals: protein. Nutrition Abstracts and Reviews, Series B 62: 787–835.
Aharoni, Y. and Tagari, H. 1991. Use of nitrogen-15 determinations of purinenitrogenfraction of digestato define nitrogen metabolism traits in the rumen. Journal of Dairy Science 74:2540–2547.
Balcells, J., Guada, J. A., Castrillo, C. and Gasa, J. 1991. Urinary excretion of allan to in and allantoin precursors by sheep after different rates of purine infusion in to the duodenum. Journal of Agricultural Science, Cambridge 116: 309–317.
Balcells, J., Guada, J. A., Peiró, J. M. and Parker, D. S. 1992. Simultaneous determination of allantoin and oxypurines in biological fluids by high-performance liquid chromatography. Journal of Chromatography 575:153–157.
Bauchop, T. 1980 Scanning electron microscopy in the study of the microbial digestion of plant fragments in the gut. In Contemporary microbial ecology(ed. Ellwood, J. N., Latham, M. J., Lynch, M. J. and Slater, J. H. ), pp. 305–326. Academic Press, London.
Buresh, R. J., Austin, E. R. and Craswell, E. T. 1982. Analyticalmethodsin15N research. FertilizerResearch 3: 37–62.
Castrillo, C, Lainez, M., Gasa, J. and Guada, J. A. 1992. The effectof increasing the proportion of barley straw in pelleted concentrate diets to lambs on rumen outflow rate and degradation of protein supplements. Animal Production 54: 59–66.
Chen, X. B., Hovell, F. D. DeB., Ørskov, E. R. and Brown, D. S. 1990. Excretion of purine derivatives by ruminants: effect of exogenous nucleic acid supply on purine derivative excretion by sheep. British Journal of Nutrition 63: 131–142.
Clark, J. H., Klusmeyer, T. H. and Cameron, M. R. 1990. Microbial protein synthesis and flows of nitrogen fractions to the duodenum of dairy cows. Journal of Dairy Science 75: 2304–2323.
Cotta, H. A. and Hespell, R. D. 1984. Protein and amino acid metabolism of rumen bacteria. In Control of digestion and metabolism in ruminants (ed.Milligan, L. P., Grovum, W. L. and Dobson, A.), pp. 122–136. Prentice Hall, Englewood Cliff, NJ.
Faichney, G. C. 1975. The use of markers to partition digestion within the gastrointestinal tract of ruminants. In Digestion and metabolism in theruminant (ed. MacDonald, I. W. and Warner, A. C. I.), pp. 277–291. Armidale University of New England Publishing Unit.
Fairlamb, A. H. 1989. Novel biochemical pathways in parasitic protozoa. Parasitology 99: (supplement) 93–112.
Ganev, G., Ørskov, E. R. and Smart, R. 1979. The effect of roughage or concentrate feeding and rumen retention time on total degradationofproteinintherumen. Journalof Agricultural Science, Cambridge 93:651–656.
Gottlieb, M. 1985. Enzyme regulation in a trypanosomatid: effect ofpurinestarvationonlevelof 3'-nucleotidase activity. Science 227: 72–74.
Jarrige, R. 1987. Situation and perspectives of the modern protein feedingsystems forruminants. In Feed evaluation and protein requirement systems for ruminants (ed. Jarrige, R. and Alderman, G.), pp. 305–326. CEC.
John, A. and Ulyatt, M. J. 1984. Measurement of protozoa using phosphatidyl choline and of bacteria using nucleic acids in the duodenal digesta of sheep fed chaffed lucerne hay (Medicago sativa L.) diets. Journal of Agricultural Science, Cambridge 102: 33–44.
Kennedy, P. M., Hazlewood, G. P. and Milligan, L. P. 1984. A comparison of methods for the estimation of the proportion of microbial nitrogen in duodenal digesta, and ofcorrectionformicrobialcontaminationinnylonbags incubated in the rumen of sheep. British Journal of Nutrition 52:403–417.
McAUan, A. B. and Smith, R. H. 1973. Degradation of nucleic acids in the rumen. British Journal of Nutrition 29: 331–345.
Mathers, J. C. and Miller, E. L. 1981. Quantitative studies of food protein degradation and the energetic efficiencyof microbial protein synthesis in the rumen of sheep given chopped lucerne and rolledbarley. British Journal of Nutrition 45:587–604.
Minato, H. and Suto, T. 1978. Technique forfractionation of bacteria in rumen microbial ecosystem. II. Attachment of bacteria isolated from bovine rumen to cellulose powder in vitro and elution of bacteria attached there from. Journal of General Applied Microbiology 24:1–16.
Mohamed, O. E. and Smith, R. H. 1977 Measurement of protein degradation in the rumen. Proceedings of the Nutrition Society 36: 152A (abstr.).
Ørskov, E. R. 1982. Protein nutrition in ruminants. Academic Press.
Ørskov, E. R. and McDonald, J. 1979. The estimation of protein degradability in the rumen from adjustedrates of passage. Journal ofAgricultural Science, Cambridge 92: 499–503.
Ørskov, E. R., Macleod, N. A. and Kyle, D. J. 1986. Flow of nitrogen from the rumen and abomasum in cattle and sheep given protein-free nutrients by intragastric infusion. British Journal of Nutrition 56:241–248.
Pérez, J. F., Balcells, J., Guada, J. A. and Surra, J. C. 1995. Contribution of dietary purine bases to duodenal digesta: effect of forage/concentrate ratio. Animal Science 60: 544 (abstr.).
Pérez, J. F., Rodriguez, C. A., Gonzalez, J., Balcells, J. and Guada, J. A. 1996. Contribution of dietary purine bases to duodenal digesta in sheep.Insitustudiesof purine degradability corrected for microbial contamination. Animal Feed Science and Technology 62:251–262.
Schelling, G. T., Koening, S. E. and Jackson, T. C. Jr. 1982. Nucleic acids and purine or pirimidine bases as markers for protein synthesis in the rumen. In Protein requirements for cattle (ed. Owens, F. N.), pp. 1–9. Oklahoma University.
Siddons, R. C., Paradine, J., Beever, D. E. and Cornell, P.R. 1985a. Ytterbium acetateasa particulate-phase digesta-flow marker. British Journal of Nutrition 54: 509–519.
Siddons, R. C, Paradine, J., Gale, D. L. and Evans, R. T. 1985b. Estimation of the degradability of dietary protein in the sheep rumen by in vivo and in vitro procedures. British Journal of Nutrition 54:545–561.
Smith, R. H. and McAllan, A. B. 1970. Nucleic acid metabolism in the ruminant. 2. Formation of microbial nucleic acids in the rumen in relation to the digestion of food nitrogen, and the fate of dietary nucleic acids. British Journal of Nutrition 24: 545–556.
Smith, R. H., McAllan, A. B., Hewitt, D. and Lewis, P. E. 1978. Estimation of amounts of microbial and dietary nitrogen compounds entering the duodenum of cattle. Journal of Agricultural Science, Cambridge 90:557–568.
Steel, R. G. D. and Torrie, J. H. 1960. Principlesand proceduresof statistics. McGraw-HillBook Company Inc., London.
Sutton, J. D., Smith, R. H., McAllan, A. B., Storry, J. E. and Corse, D. A. 1975. Effectsof variations in dietary protein and supplements of cod-liver oil on energy digestion and microbial synthesis in the rumen of sheep fed hayand concentrates. Journal of AgriculturalScience, Cambridge 84: 317–326.
Zelaya, J. C. 1994. Degradatión ruminal de las bases púricasdeorigen alimentario. Tesis-Master of Science. Instituto Agronómico Mediterraneo de Zaragoza.
Zinn, R. A. and Owens, F. N. 1982. Rapid procedure for quantifying nucleic acid content of digesta. In Protein requirements forcattle, symposium (ed. Owens, F. N.), pp. 26–30. Oklahoma State University, Stillwater.