Seth_ia - 8/8/2013 00:39 University of Minnesota says to use 5# per 100,000 gallons of manure. Usually I treat for full pit capacity, as i figure that your largely just treating the surface anyway. Remember the Rumensin is toxic to pigs. I always suggest putting it in the pump outs only, though that is a little slower to work. Also I wouldn't suggest More than Manure. I've seen it added to a barn with foam. It did nothing and then still needed Rumensin. Good luck!