Dr Cooks leather bitless bridle on Tennessee Walking Horse Dr W R Cook, a UK-trained equine vet, first marketed The Bitless Bridle™ in the USA in 1999. It is the only bitless design that has been developed and physiologically validated by a respected veterinary surgeon, one who has focussed 50 years of his research on the mouth, ear, nose and throat of the horse, particularly unsoundness of wind, the cause of bleeding in racehorses and the harmful effects of the bit method of communication.