Technical Abstract: Soybean and maize are extensively used in animal feed, primarily in poultry, swine, and cattle diets. Soybean meal can affect pig performance in the first few weeks following weaning and elicit specific antibodies in weaned piglets. Though maize is a major component of pig feed it is not known if any of the maize proteins can elicit immunological response in young pigs. In this study, we have identified a prominent 27 kDa protein from maize as an immunodominant protein in young pigs. This protein, like some known allergens, exhibited resistance to pepsin digestion in vitro. Several lines of evidence identify the immunodominant 27 kDa protein as a '-zein, a maize seed storage protein. First, SDS-PAGE analysis of different solubility classes of maize seed proteins revealed the presence of an abundant 27 kDa protein in prolamin (zein) fraction. Antibodies raised against the purified maize 27 kDa '-zein also reacted against the same protein recognized by the young pig serum. Additionally, matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of the peptides generated by trypsin digestion of the immunodominant 27 kDa protein showed significant homology to the maize 27 kDa '-zein. Results from two experiments conducted to determine the effect of eliminating maize from the animal feed demonstrated that replacing maize with rice improved young pig’s body weight at 21 days in nursery by 8%, daily gain by 16%, and gain efficiency by 4%. Since eliminating the allergenic protein will have a great impact on the nutritive value of the maize meal and expand its use in livestock industry it will be highly desirable to develop maize cultivars completely lacking the 27 kDa allergenic protein.