The only reasons I've ever seen for avoiding horse manure are the number of weed seeds that are undigested and ready to sprout, and the idea that it's too "hot" none of which seem to make sense to me. I know people who use it all the time., after it's been composted a bit. Adam in Glenview, IL USDA Z 5 where the sun's coming out after the snowstorm has passed. Crocuses, galanthus and Siberian squill up and blooming, Arums up and not yet flowering-- and hellebores and hyacinths in bud.