Bees do not like horse or mule sweat. If the animals can get away by running they will do so, but confined horses/mules can be killed.

I had a shetland pony for my kids, left the bee yard gate open one day when working the bees. Left for lunch, the little mare went into the bee yard, got around behind the hives away from the gate and knocked over a hive. Before I found her she was stung so badly that she died. Spent the rest of that day cutting wood for her funeral pyre. Then I had to tell the kids.