Hi,
Are mules always sterile? I am wondering because I know a very nice mule. Please help!

I only know of one who wasn't. The only foal produced by it was named Blue Moon. So that should tell you it was a rare occurance!

Yes in General they are sterile. There is that rare exception once in a great while. But they can carry a foal. How you ask? Through embryo transfers. As long as the Molly cycles (comes in & out of heat) they can be synced up with a mare and an embryo transfer can be preformed at day 7. They flush the embryo out of a mare and transfer it to a Molly. The molly is then put on progesterone for several months and is checked at day 14 for pregnancy. Once she is confirmed pregnant some are kept on progesterone for several months before taken off. They foal out as normal and can nurse the foal through weaning time just like a mare. Studies have shown this is successful in Molly's who cycle, But they have had no luck in Molly's that don't cycle.

Hope this helps.

Another thing to keep in mind is mules are the only ones who have been proven to be able to reproduce even once in a blue moon (as far as I can find). Hinnies have not so far.

In "AMERICAS HQRSE" ( I cannot remember which issue) tells a story of a Molly mule that was kept in the stud pasture and the next spring, surprised her owners with a foal! No embryo transfers, no progesterone, no nothing... quite interesting...