Conséquences des nouveaux «systèmes d'unités phosphore» sur la formulation des régimes

Abstract

The tables published by INRA-AFZ in 2004 supply several new feedstuff characteristics concerning phosphorus (P), which have been integrated in new «phosphorus unit systems» for different animals, particularly for ruminants, pigs and poultry. The utilisation of such systems was studied here in the formulation of compound feeds for growing pigs by linear programming. The new system (INRA-AFZ, 2004) was compared to the previous one (INRA, 1989). Several models were proposed in order to take the action of vegetal and microbial phytases into account. First, a linear effect of microbial phytases on the liberation of digestible phosphorus was studied. Then, microbial phytasic activity was tested through a non-linear relation with an interaction between vegetal and microbial phytases. Moreover, the amount of excreted P was considered in the model. Its economic consequences varied between the situations. With this new feeding system, pig diets are formulated closer to the animal's needs in terms of digestible P and with a lower level of mineral supplementation. The quantity of total P in the diets and, therefore, animal P excretion are reduced.