Phosphorus loss from soils fertilized with animal manures has been implicated in the degradation of water quality. Assesment stratagies aimed at reducing P loss from animal manure applications should incorporate the potential impact of dietary modification on P loss to water resources. The objectives of this study were to determine how dietary modification in animal feed and manures from different sources (dairy, swine, and poultry) impact total P, water soluble P, HCl-extractable P, and organic forms of P in manure samples. Organic P in manure samples were assayed using ion chromatography. The results and implications of this study will be presented in this poster.