Which digestible phosphorus requirements for growing and finishing pigs ?

Different digestible phosphorus contents in growing and finishing diets were compared in agreement with usual on-farm conditions and in the context of the feedstuff availability in France. The digestible phosphorus level in the control diet was determined according to the factorial approach of requirements, applied to consumption and daily gain curves obtained from a previous batch. These levels were 2.25 and 1.85 g/kg in the growing and the finishing periods, respectively. Three experimental diets, two with a lower content (90 and 80% of these control levels) and one with a higher content (above 110%) were compared to the control diet. The changes in dietary phosphorus content had a limited impact on pig performance during growing and finishing periods. However, according to our results, the risk to reduce performances was higher when the supply decreased below 90% of the estimated requirements. The assessment model of digestible phosphorus requirements used in this study allows a precise determination of pig’s requirements during growing and finishing periods. However, the use of this method in practice, requires knowing precisely pigs performances and intake, which is often difficult to obtain. It is why it is still common to advice the use of average recommendations to satisfy pigs requirements. It can be concluded from our study that the optimum contents vary between 0.21 and 0.23 g/MJ net energy in growing period and 0.17 and 0.19 g/MJ net energy in finishing period.