Summary An experiment was designed to determine the soya antigen levels in milk replacers above which gastrointestinal disorders appeared in preruminant calves previously sensitized to antigenic soya by feeding a soya‐based milk replacer for 3 months. These calves were then equipped with wire electrodes on the duodenum and the mid‐jejunum. The sensitization was visualized using direct skin testing, plasma anti‐soya antibody determination and intestinal myoelectric activity recording. After sensitization, the calves were occasionally fed liquid test meals containing various proportions of antigenic soya and whey. The soya‐fed calves displayed larger 24 h skin reactions to β‐conglycinin and higher plasma anti‐soya antibody titres than the controls maintained on a skim‐milk based milk replacer. Disturbances of the myoelectric activity patterns were recorded on the duodenum and mid‐jejunum after feeding antigenic soya, but not nonantigenic soya or milk protein, in the soya‐sensitized calves. When the level of antigens was varied, disorders in the jejunal motility patterns appeared when antigenic soya provided one‐third or more of the dietary protein in the test meals, although some abnormalities were evident at lower incorporation rates. The major change was a reduction in the mean duration of the jejunal migrating motor complexes which was essentially accounted for by a decrease in the mean duration of the phase I (quiescence). This level of antigens corresponded approximately to 14 and 12 mg of immunoreactive glycinin and β‐conglycinin respectively, per gram of protein intake, i.e. 80 and 70 mg/kg0.75 per test meal.