In order to get a mule a jack (male donkey) is bred to a mare (female horse).
A hinny is the result of breeding a stallion (male horse) to a jenny (female donkey).
Since the offspring inherit extremity characteristics from the sire, mules tend to have longer ears, smaller feet, less plush tails and manes, while hinnies tend to be more horse looking.
The resulting offspring is sterile, although sexually normal in behavior.
Male mules and hinnies are always gelded.
Female mules and hinnies will experience estrus.