A method is described for improving the nutritional value of a foodstuff comprising a source of myo-inositol hexakisphosphate by feeding the foodstuff in combination with a phytase expressed in yeast. The method comprises the step of feeding the animal the foodstuff in combination with a phytase expressed in yeast wherein the phytase can be selected from the group consisting of AppA1, AppA2 and a site-directed mutant of AppA. The invention also enables reduction of the feed to weight gain ratio and an increase bone mass and mineral content of an animal. A foodstuff and a feed additive comprising AppA2 or a site-directed mutant of AppA are also described.