Fermenting their feed and feeding that mash really made a difference for my birds. Use a 5 gal pail, add 4 qt feed, fill with water towithin 2 inches of top and add 1/4 cup unpasturized apple cider vinegar. Stir 2-3 times a day for 4 days, then feed out 1/3. split the remaining amt between 2 5 gal pails. add feed, and fill with water and stir. use one a day while the other is brewing. I also fed dry as needed but overall had much better poo and less stink.
Doesn't reduce the poo though-- cornish x eat a LOT and poo a lot.
x2 This is the perfect way to cut down on smell as well as keep them healthy. Feed in 5' rain gutter thats stabilized. Easy peasy.