Chen Chundao, a team of experts from the University of Missouri, the University of North Carolina, Purdue University, the University of Michigan and the University of Oklahoma, believes that using synthetic amino acid feeds to feed pigs can reduce the odor of pigs excreting fecal matter. According to a preliminary study by the Joint Research Group, Gary Airy of the University of Missouri believes that, like all animals, pigs need large amounts of amino acids to synthesize proteins to ensure rapid growth and life extension. However, when pigs consume natural feeds such as corn and oats, they will accumulate large amounts of excess amino acids. These excess amino acids serve as a source of odor, particularly odor, in excrement. If synthetic amino acids are used to feed pigs, the excess amino acid content in pigs will be greatly reduced, and the faecal smell will be significantly reduced. After tests, if the natural feed for corn, oats, etc., is reduced by 14% to 18% in pig feed, and an appropriate amount of synthetic amino acids is added at the same time, the content of ammonia in swine manure will be reduced by 30% to 50%. It can be basically eliminated and it will not affect pig growth and development. At present, experts from the Joint Research Group also use this technique in poultry farms because poultry broilers also experience problems with fecal odor.