Two weight classes of growing-finishing swine were fed corn-soybean diets lower in protein and phosphorus to determine the reduction in nitrogen (N) and phosphorus (P) in swine waste when compared to pigs fed a conventional diet. For the two weight classes, total N waste was reduced 32% and 25% while total P excretion was reduced 39% and 38%. The experimental results were used to calibrate the NCPIG model to predict N and P excretion levels. Model excretion values for the same diets showed similar trends in mineral reduction by diet, but were higher for urinary N when compared to observed values. A portion of this difference in urinary N was attributed to lower body maintenance of the experimental animals. The impact of the lower protein and phosphorus diets was evaluated over the growing-finishing period using the NCPIG model. Model results showed an approximate reduction of 44% in total N and P excretion when compared to the conventional diet with little impact in time of production. The results of this project indicate that diet manipulation is a viable tool for U.S. swine producers in maintaining a sustainable U.S. swine industry.