A problem that seriously impacts both the swine and soybean industries is the adverse reactions of young piglets to soy based rations. The responses of early-weaned piglets to soy-based rations are transitory decreased performance, reduced food intake, and slower growth rates due to transitory hypersensitivity to certain proteins in soybean meal compared to animals provided alternate nutritional sources. These reactions are attributed to the development of immune-mediated allergic responses and inflammation of intestinal epithelium. Reduced piglet growth and development has been ascribed in part to secondary microbial and viral infections in the epithelial cell layers of the digestive system that accompany the immune response and inflammation. Two approaches were initiated to address these problems. One was to breed swine populations from which neonatal piglets can be obtained that either lack or exhibit immune-mediated hypersensitivity upon exposure to soy-based rations. The second was to develop soybeans whose compositions differed markedly with respect to known seed allergens, and then to use these proteins to ascertain whether these differences could be perceived when the two groups of neonatal piglets were exposed to them. To facilitate the detection of an immune-mediated response, an assay was developed to measure the appearance of soy-specific antibodies in serum from piglets challenged with soy protein. Although only 2 of 5 planned generations of breeding and selection were complete at the termination of the NPB/USB supported project, two conclusions can be drawn based upon preliminary evaluation of piglets from the two breeding populations. One is that the adverse reaction of early weaned pigs to soy rations may be reduced or eliminated through swine breeding, and the second is that it is possible to produce swine populations that are superior to existing animal models for the study of legume allergy.