Reprod. Nutr. Dev. 43 (2003) 271-284
DOI: 10.1051/rnd:2003020

II. Quantitative aspects of phosphorus absorptionin ruminants

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

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

(Received 17 December 2002; accepted 12 June 2003)

Abstract
Phosphorus absorption in ruminants was analysed from a database described in a previous article. For common values of ingested phosphorus (2.5-5.0 g kg ^-1 of DM), 0.73 of dietary phosphorus is absorbed. The remaining variability is probably due to phosphorus quality. Phosphorus absorbed from silage, cereal, cereal by-products and hay differs greatly. The current true absorption coefficient used to calculate daily phosphorus supply is a constant value in the current systems and often it underestimates the true absorption resulting in an excess of phosphorus being supplied in the diets. Adjusting the true absorption coefficient values requires better characterisation of the phosphorus supplied by each feedstuff. Dietary influences (phytate phosphorus, crude fibre, etc.) were investigated but trials assessing the ration effect on phosphorus absorption are lacking. Since rumen microbes have specific phosphorus requirements, particularly for cell-wall degradation, the feedstuff phosphorus availability for the rumen ecosystem is discussed.

Key words: absorption / availability / phosphorus / quantitative aspect

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

© INRA, EDP Sciences 2003