BackgroundCattle are commonly fed soybean meal (SBM) and accidental intoxication sometimes occurs.ObjectivesTo describe the biologic and clinical features ofSBMintoxication.AnimalsFour steers with ruminal cannula.MethodsControlled experimental trial.SBMwas administered once at 1 and 2% of body weight (BW) via cannula at 2‐month intervals.ResultsThis study showed a 2‐phase pathogenic course for 2%BW SBMintoxication. The 1st phase (until 10 hours post‐administration) is restricted to ruminal modification with volatile fatty acid overproduction and moderate ruminal ammonia concentration. In the 2nd phase (12–22 hours post‐administration), ruminalpHreturned to initial values and marked ammonia accumulation occurred in blood, inducing severe metabolic alkalosis with hyperglycemia, hyperinsulinemia, and delayed aciduria (30–40 hours post‐administration). Among the clinical signs, nervous signs were only observed during the period with increased plasma ammonia concentration. At 1%BW, ruminal and blood modifications were less pronounced than at 2%BW, and clinical signs were not observed.Conclusions and Clinical RelevanceAmmonia accumulation in blood during the second phase is the consequence of continued ammonia production, decreased carbohydrate fermentation, and overwhelming of hepatic detoxifying capacity. Because ammonia accumulation is associated with the clinical signs, treatment ofSBMintoxication could be similar to treatment of urea intoxication, including rumenotomy, oral administration of cold water and vinegar, and measurement of ruminalpH.