This invention provides botulinum antitoxin compositions and methods of production, and methods of treating animals and humans prophylactically and also those suspected of having contacted botulism toxin. The botulinum antitoxin is prepared by inoculating an animal with a monovalent botulinum toxoid and toxin. The animal's plasma is collected and purified at a high pH by affinity chromatography. The resulting monovalent immunoglobulins are de-speciated by digestion with pepsin. Monovalent antitoxins for all seven botulinum serotypes are then combined to produce a high titered heptavalent botulinum antitoxin composition.