I dont have 20 years experience with chickens. I started raising chickens and hogs in 1979. I got out of it in 1985 due to military deployment. I didnt get back into chickens til 2004, no hogs this time. Back in the early 80's, my chickens were purchased from the feed store as chicks and they never made it past a year old, always in the freezer, I had a bunch of younguns to feed. There wernt any favorite chickens, only the ones on the dinner plate. It was the same with the hogs. I had close to 30 head at one time, all duroc's. I'd sell most of them, save a few for the freezer each year, always had a boar and sow or two for breeding. I never treated the chickens for anything, never wormed them, they didnt live long enough to get anything. I wormed the hogs only once and that was with Red Devil lye. I'd put a 50 pound sack of corn into a 55 gallon drum, fill it half full of water, add 1 tablespoon of the Red Devil lye and stir it real well with a boat paddle. Once in awhile we'd go hunting using bay dogs and pit bulls to catch piney wood rooters...now that was fun. We'd sell the hogs, which in turn were sold and shipped out to another state and released in a hunting preserve....something you see advertised in the back of a hunting magazine that rich folk would gladly pay for a guaranteed hog hunt.
I dont eat my chickens now, kids are grown and gone. I'm a softie now, I consider them all as my pets and I have several favorites (and that number is growing.)