Yeah, I saw similar numbers from EPA docs when I decided I might want to back up my comment, thanks :) but what I'd like to know is what the median size of a dairy farm in the US is, and what proportion of the milk we drink comes from larger operations like those described here, with head counts of 15-20,000: http://en.wikipedia.org/wiki/Dairy_farming#Animal_waste_from...
(Of course I know Wikipedia isn't the most reliable and those specifics seem to be lacking citations)
http://www.michigan.gov/documents/deq/wb-npdes-CAFO-rules-fi...
I know that farms much smaller than that have to abide by some of the CAFO rules such as having approved manure application plans.
Several of Michigan's larger farms use the manure to generate their own electricity.