Does Chullin 71A (where it says do not cross bread animals) mean Jews should not breed mules?
Jews may not breed mules. They may breed mules one with another provided they are both born of the same species (i.e. both mothers are donkeys).
D. Zupnik
Breeding implies progeny. Mating is really what we are talking about on the daf.
The Mule is a cross between a donkey stallion (called a jack) and a horse mare. Hinnies are just the opposite - a stallion horse crossed to a donkey jennet. For all purposes, hinnies and mules are classified and shown together under the general term Mule. A mule or hinny may be a male (horse mule or horse hinny) or a female (mare mule or mare hinny). Sometimes horse mules (the males) are called Johns, and the mares are called Mollies. Both male and female mules have all the correct "parts" but they are sterile and cannot breed. A VERY few (about 1 in 1 million) mare mules have had foals, but these are VERY, very rare. No male mule has ever sired a foal. SO if you cross a mule to a mule - you get nothing!
Michael