I also have access to free horse manure, and add about 300kg of to our 1 acre farm every week. I hot compost the manure headed for the vegetable garden (usually combined with green landscaping waste), but apply bags of the stuff directly around fruit
trees, where it composts in place. I don't add direct to my vermicompost. In my experience it has been really amazing as mulch/slow release nutrition for fruit trees. Hot composting is really important for annuals not only because of potential 'cides in the manure, but also because otherwise a huge number of weed seeds germinate. So now, when I add directly around trees, I make sure something is on tap to grow over the manure, to shade the ground and allow for mycelial growth. I have a lot of
mushrooms that grow on the manure when it's NOT hot composted-- not as much when it has been. I also apply manure directly to our goat pastures (no goats yet) then
water to get oat hay started...might as well use the weeds as an asset...