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Relationship between urinary purine derivative excretion and milk protein yield by dairy cows

  • R.J. Dewhurst (a1), R.T. Evans (a2), V.J. Theobald (a2), M.A. Neville (a2), S. Miles (a2) and A.B. McAllan (a1)...


The ability to predict microbial protein yield in any feeding situation is important in maximising the utilisation of feed nitrogen since it will guide decisions as to whether to take steps to improve rumen function or provide supplementary undegradable protein (UDP). The UK Metabolisable Protein (MP) system (Agricultural and Food Research Council, 1992) predicts the yield of microbial protein from the rumen according to the supply of Fermentable Metabolisable Energy (FME). This has led to an improved understanding of responses seen on farms, though there remains uncertainty about microbial protein yield. The excretion of purine derivatives (PD), allantoin and uric acid, in urine has been used as a non-invasive index of microbial protein flow to the duodenum (Chen et al, 1990) and might form the basis of an on-farm diagnostic test. In earlier work, with spot sampling of urine (Dewhurst et al, 1994), we have shown a relationship between milk protein yield and urinary PD excretion; the current work extended these studies by utilising 6-day total collections of urine.



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Agricultural and Food Research Council (1992). Tcorn report no.9. nutrient requirements of ruminant animals: protein. Nutrition Abstracts and Reviews 62B: 787835
Aston, K., Dewhurst, R.J., Fisher, W.J., Davies, D.W.R. and McAllan, A.B. (1995). Effects of sources of carbohydrate and protein given at low levels with grass silage ad libitum on the performance of lactating dairy cows. Animal Science (in press: this meeting).
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: 131142
Dewhurst, R.J., Offer, N.W. and Thomas, C. (1994). Urinary purine derivative excretion and milk protein production by lactating dairy cows. Proceedings of the Society for Nutritional Physiology 3: 236A
Lux, O., Naidoo, D. and Salonikas, C. (1992). Improved hplc method for the simultaneous measurement of allantoin and uric acid in plasma. Annals of Clinical Biochemistry 29: 674675
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Proceedings of the British Society of Animal Science
  • ISSN: 1752-7562
  • EISSN: -
  • URL: /core/journals/proceedings-of-the-british-society-of-animal-science
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