A hinny is a domestic equine hybrid that is the offspring of a male horse and a female donkey (called a jenny).Hinnies are on average slightly smaller than mules. The size difference between mule and hinnies is merely physiological, due to the smaller size of the donkey dam, as compared with a much larger mare. Others claim it is genetic, but the view of the American Donkey and Mule Society
Mule, which is the product of a female horse and a male donkey.Thus, a hinny is restricted to being about the size of the largest breed of donkey. Mules, however, have a female horse as a parent, so they can be as large as the size of the tallest breed of horse. There are some very large mules, mostly from work horse breeds such as the Belgian.