Phosphorus (P) is a limited resource, and optimizing its use requires increasing the use of phytic P (PP), the main form of P stored in plants. Calcium (Ca) is supplied mainly as calcium carbonate, known for its strong buffering capacity. This property may explain the negative effect of Ca on the use of PP and other minerals such as zinc (Zn). However, the complexity of interactions among PP, Ca, and Zn makes it difficult to quantify their in-vivo bioavailability. The objective of this study was to simulate intestinal fluxes of Ca, P, and Zn in growing pigs using a mechanistic model. We developed a mechanistic model that described the fate of Ca, Zn, and the soluble and insoluble forms of P in the stomach and small intestine. Gastric pH, a key factor in PP hydrolysis by phytases, was mechanistically represented by representing gastric secretions and the buffering effects of meals. Direct effects of Ca and Zn on PP solubilization were also represented, which highlighted their marginal effects on the efficiency of PP degradation by microbial phytases. Attention was given to modelling Zn fluxes in the intestine (of both dietary and endogenous origin), as this is the main site at which Zn metabolism is regulated. The model simulated 24 h periods, and the apparent digestibilities of the minerals that it predicted were compared to those observed in the literature.