Genetically engineered pigs, EnviropigsTM, use efficiently phytate phosphorus (P) in cereals and excrete a small amount of P in manures. Understanding P composition of the manures in relation to availability to plants and susceptibility to losses is essential to exercise regulatory processes of the technology and to develop BMPs. We sequentially extracted manures to separate P into various inorganic (Pi) and organic (Po) fractions, including water Pi & Po (Water-Pi & -Po), NaHCO3 Pi & Po (Bicarb-Pi & Po), NaOH-Pi and Po (NaOH-Pi & -Po), HCl-Pi, and Residual P (Res-P). Manure samples were collected from four combinations of two genotypes (conventional pig - CP and transgenic pig - TP) with two types of diets (conventional diet - CD and low P diet - LPD). Compared with CP, TP decreased total P in manure by 4.2% when fed with CD and 57% when fed with LPD. Deceases of P contents in manures were primarily in labile P extractable with water and NaHCO3, which accounted for 94% (Pi: 84.7%; Po: 9.3%), followed by stable Pi (HCl-Pi), which accounted for 5.9%. TP did not affect NaOH-P in manures, regardless of the type of diet. TP increased significantly N:P ratio of manure, and appeared more suitable to meeting crop N and P needs than the CP. Adoption of the Enviropig technology can be an environmental friendly approach to reduce both seasonal soil P loss after application and long-term soil P build-up, while posing great potentials for the enhancement of livestock industry.