The withers's the highest point on the back of an upright animal, on the ridge between its shoulder blades. Horses The withers in horses are formed by the dorsal spinal processes of roughly the 3rd through 11th thoracic vertebrae (most horses have 18 thoracic vertebrae), which are unusually long in this area. The processes of the withers can be more than 12" (30cm) in height on the average horse. Since they don't move relative to the ground (as does the horse's head), the height of a horse's me… (More on Withers)