Technical Abstract: Non-point phosphorus (P) pollution arising from the application of animal manure is becoming a serious global problem. Reducing the amount of P excreted in the manure by changing diet or animal metabolism through genetic engineering may help mitigate this problem. Currently, there are many unanswered questions associated with transgenic pigs and the potential changes in their feces. This study examined the detailed chemical structure of swine feces as affected by genetics, diet, and growth stage. New, advanced solid-state nuclear magnetic resonance (NMR) techniques were used to characterize the feces. Different spectral editing techniques were used to identify specific functional groups. Quantitative NMR techniques were used to quantify the different functional groups and 2-dimentional **1H-**13C heteronuclear correlation NMR was used to detect their connectivities. Feces from conventional and transgenic pigs had similar residual peptide, carbohydrate, and fatty acid components, while those from transgenic pigs did contain more carbohydrates and fewer nonpolar aliphatics. There was no consistent effect of diet (conventional versus low-P) or growth stage (growing versus finishing stage) on chemical structure of the feces. This research provides an initial step toward evaluating potential environmental and health risks associated with transgenic pigs.