This study intends to further develop a well tested pig growth and nutrient utilization model and to develop an easy to use decision support tool. These tools can be sued for improving profits and optimizing nutrient use and help make general management recommendations. The results of this study improved a well-tested and full-scale, dynamic, biological pig growth model, which has been expanded to reflect the pig’s response to the use of phytase and PayleanTM in the diet, to represent between animal variability within groups of pigs, and to increase flexibility in defining alternative shipping strategies. The model generates and records growth curves, changes in feed intake, carcass composition, phosphorous and nitrogen retention and economic returns for 1000 individual pigs within a group, and allows weekly sorting of market pigs for shipment. A simpler model was also made that is supposed to act as a decision support tool. The user can enter specific costs, prices and carcass grading systems and use the model to identify which management scenario maximizes dollars per pig.