Modélisation du besoin en calcium et variations du rapport phosphocalcique de l’aliment selon le niveau de performance de la truie reproductrice

Due to the cost of dietary phosphorus supplements and consequences of phosphorus supplied in excess on the environment, a strong trend towards improved adequacy between its supplies and requirements has been observed for a while in reproductive sows. Conversely, calcium supplements are presently inexpensive, and dietary calcium content is not limited by any regulation. As calcium and phosphorus interact in the digestive tract and in their metabolism, their supplies need to be balanced. Based on available literature on phosphorus (large) and calcium (scarce), a model was developed that assesses calcium requirements in reproductive sows. Phosphorus can be supplied on a digestible basis with reference to available systems and tables of nutritive values of feedstuffs, but this is not presently the case for calcium. Consequently, different hypotheses for calcium digestibility are used in the model, which will need to be updated (as will the definition of the maintenance requirement) as soon as the feedstuff tables have been documented with this criterion. Given this limitation, the model is used to investigate the effect of physiological stage and productivity level (prolificacy, milk production) on the daily requirement of total calcium. As the degree of bone mineralisation is not considered, the model cannot be used to simulate consequences of inadequate supplies of calcium or phosphorus. ; Le coût élevé des sources de phosphore et l’impact d’un apport en excès de cet élément sur l’environnement conduisent à restreindre les apports en phosphore aux besoins chez la truie reproductrice. Au contraire, les sources de calcium sont peu onéreuses et, en l’absence de contrainte de teneur maximale sur cet élément, sa teneur peut être assez élevée dans les aliments. Phosphore et calcium doivent pourtant être apportés de façon équilibrée. Un modèle est proposé pour estimer les besoins en calcium de la truie reproductrice sur la base des connaissances disponibles, beaucoup plus limitées pour cet élément que pour le phosphore. ...