This is what works for me.
I use horse manure because it is free, having five horses we have an endless supply of the stuff. My wife also uses wood shavings in the stalls for bedding but this can pose a problem if it's not managed properly.
Wood shavings contain huge amounts of horse urine which leads to high levels of ammonia, I'm not sure if composting breaks down the ammonia but I don't take any chances so I spread the shavings out in an area on our property so the sun can break it down, then it goes into the compost pile. If you purchase or get your manure from someone else, look for bedding materials (wood shaving, straw and wood pellets) mixed in the manure, if it has an ammonia smell to it, look somewhere else.
Compared to the commercial organic and chemical fertilizers we have available to us today, horse, pig, cow, etc manure are not a very good source for nutrients, in fact if you're not supplementing your grow site with nitrogen you may end up with a nitrogen deficiency!
But I don't use it for it's fertilizing properties, I use it along with gypsum to amend our suck ass clay soil.
Just my 02