The study was conducted to evaluate the biologicalflow of P in pigs fed diets based on corn, soybean meal, defatted rice bran(DRB) and soybean oil, with increasing phytase levels (253, 759, 1265 and 1748PU/kg of diet), using mathematics models. The model was deterministic and compartimental,in which the gastrintestinal tract (GIT) (C1), the plasma C2,the bones (C3) and the soft tissues (liver, heart, kidney and muscle)(C4) represented the compartments. Metabolism data and kinetics ofP in tissues were used in the model, obtained by the isotopic dilution technique.The parameters used were: absorption, retention, endogenous P that return tothe gastrintestinal tract (GIT), dietary absorbed P, accretion, reabsorption,balance of P in bone and soft tissues and P from total absorbed that returnedthe GIT. The biomathematical model used is adequate to explain the P flow ingrowing pig. The phytase enzyme interfere in biological flow of P from compartmentC1 to C3 and with the output flow of P from compartmentC3 and C4 to C1. The level of 759 PU of phytasein diet of growing pig availability more efficientily the organic phosphorusfor the pigs metabolism.
