The objectives of this study were: To determine the solubility and reactivity of manure P from phytase amended diets in Manitoba soils. To develop techniques that can be used to assess the environmental reactivity and mobility of manure P. To obtain a better understanding of the relationship between increased dietary efficiency of
feed P, animal performance and reduced environmental impact of manure. It was demonstrated in this study that it is possible to completely remove inorganic P from animal diet and have no negative impact on the performance of the animal if the diet is supplemented with adequate amounts of phytase. The digestibility and retention of N and P improved with phytase supplementation leading to reduced manure P content. Overall, the addition of phytase to swine diets reduced the total and labile P in the manure and feces and this will reduce P loading when manure from phytase mended diets is added to the soil. This management practice has the potential to reduce the loss of P from soil to
surface water, as such, swine producers in Manitoba should be encouraged to use this technology as part of their manure management strategies. This study also shows that phytase supplementation had no effect on the solubility of manure P in representative Manitoba soils. However, in the absence of inorganic P, solubility of
manure P increased in calcareous soil mainly due to a lack of calcium in the manure. It may
not be environmentally prudent to eliminate all the inorganic P from swine diets due to its
possible impact on increased manure P solubility in certain soils.