I get 25 gallon/cow/day. That is liquified manure. I don’t know what the ratio would be...it would take a lot of added water to make the manure from my 3 horses liquid.
” A mature dairy cow weighing 1,400 pounds can generate around 14 gallons (about 120 pounds or 1.9 cubic feet) of feces and urine each day with an average as-excreted solids content of around 12 percent.”
http://www.extension.org/pages/15476/liquid-manure-storage-ponds-pits-and-tanks#.VLsKtB1ozgE
So less than a 50:50 water addition would get you to the figure cited.
That sounds more like it. Musta got an extra zero on my calculator