When you say "slow"birds what breed are you referring to? I do cornish roasters from murray mcmurray and though they grow very quickly with a great feed conversion (did a few males the other day and they dressed out at 5# 11oz at 7 weeks old) they're not a very appealing bird in any other way; they won't range around and scratch for insects or plants but instead lay on their enormous breasts and get filthy with their own droppings. They're actually a lot of work just to keep fairly clean because of this. Their meat while plentiful is nothing to rave about. I have a feed mill down the road that makes a nice quality feed but they're not interested in anything else so the meat kind of reflects this. I read about a breed called "freedom ranger" by one hatchery and "Colored Range"broilers by j. m. hatchery in PA that is supposed to have a nice feed conversion ratio, is hardier, and will range around. Is this what you have?