Reprod. Nutr. Dev. 43 (2003) 285-300
DOI: 10.1051/rnd:2003021

III. Quantitative aspects of phosphorus excretionin ruminants

David Bravo^{a, b}, Daniel Sauvant^a, Catherine Bogaert^b and François Meschy<sup>a

a</sup>  UMR INRA-INAPG, Physiologie de la Nutrition et Alimentation, 16 rue Claude Bernard,75231 Paris Cedex 05, France
^b  UNION IN VIVO Ets INZO°, Chierry BP 19, 02402 Château-Thierry Cedex, France

(Received 17 December 2002; accepted 27 May 2003)

Abstract
Ruminant phosphorus excretion and metabolism were studied through a database. Faecal endogenous phosphorus is the main pathway of phosphorus excretion and averages 0.85 of total faecal phosphorus. The remaining 0.15 is unabsorbed dietary phosphorus. Faecal endogenous phosphorus is mainly unabsorbed phosphorus, with saliva being the major source, and is correlated to factors influencing saliva secretion (DM intake, physical dietary characteristics and dietary phosphorus content). Another source of faecal endogenous phosphorus is rumen microbial phosphorus that escaped solubilisation during post-rumen digestion. All factors stimulating microbial growth would increase phosphorus uptake by the rumen microbes and consequently the faecal endogenous phosphorus. Understanding the determinants of faecal endogenous phosphorus flow will help to precise the determination of net phosphorus requirements for maintenance. The role of plasma phosphorus in urinary phosphorus loss is discussed.

Key words: excretion / phosphorus / quantitative aspect / ruminant

Correspondence and reprints: David Bravo
    e-mail: dbravo@inzo-net.com

© INRA, EDP Sciences 2003