BACKCOUNTRY said:If the horse manure is hot composted, it should kill most of the weed seeds.......but either works great. I have used mostly cow, Horse, llamma, and Sheep manure for growing my plants through the years.
They are weak in the NPK department, as wally mentioned, so you need to use them in gallon ammounts rather than by the cup like with more potent manures like Chicken manure for example.
Last year I used about 3-6 gallons of llamma manure per cannabis plant, in large ammounts the nitrogen content is where you need it, plus it helps alot to condition the soil, to soften it and help hold moisture and any other fertilisers that may be used.