Anaesthesia may produce nausea and vomiting so some animals should be fasted before surgery. Dogs, cats, non-human primates and ferrets vomit. Pigs sometimes vomit. Withholding food for 8h is usually sufficient to prevent vomiting. Sheep and other ruminants regurgitate and withholding food may not reduce this.
Vomiting or regurgitation during the onset or recovery from anaesthesia can have serious consequences, as the protective coughing reflexes that are present when an animal is fully conscious may have been lost. This can result in material being inhaled into the lungs, causing severe pneumonia.