There are vacuum cleaners especially for horses - they cost a bundle. They can be found in any horse supply catalogue.
Or you can buy a shop vac and let it multi-task
Except for my husband's shop vac that is ---- it has taken up permanent residence in the horse barn
Get the horse used to it a little at a time.
Whatever you do, DON"T vacuum the family jewels and keep it away from the eyes unless you have a horse that thinks it's at the day spa