A friend of mine has recently had to move and he left me his birds and now I have way too many birds for my chicken compound and I was wondering what is the latest age you can butcher birds at and they will still be good eating. The breeds I am thinning out are 5 Ayam cemani, 2Russian Orloff, 1 jersey giant and 5 to 6 Italian reds
It depends on how you want to cook them. Coq au Vin is how the French make a gourmet meal out of a really old rooster, about as tough a bird as you can get. Chicken and Dumplings is American soul food. Chicken soup supposedly has curative properties, not sure about that. Crock pots and pressure cookers can go a long way toward tenderizing an old chickens. Old roosters make the best broth but old hens come in second as far as broth quality, at least in my opinion.
If your only thoughts on cooking chicken are fried, grilled, or roasted, forget it. Send an old bird to the landfill unless you can bury it somewhere a dog, coyote, or some other critter won't dig it up and scatter it.
I bury the offal in the garden but for me not at least making broth would be a waste. To make broth cut the bird into pieces that will fit in a large crock pot, use half a bird per batch. Put in a bay leaf, a dozen peppercorns, a chopped carrot, chopped celery, chopped onion, garlic, and some herbs (I use basil, oregano and occasionally thyme or parsley), cover that with water and cook on low overnight, from 12 to 18 hours, longer if you wish. I've heard some people say they go three days. Strain and de-fat the liquid, that's better than the most expensive broth you can buy. Pick the meat, a lot will probably have fallen off the bone. If you include the back and neck, be a bit careful as you may find some small bones. Use that meat in tacos, stews, soups, or casseroles. It will take some time to strain and de-fat the broth and to pick the meat, plan that for when you have time.
What is the latest age you can butcher birds and still get good meat? That's limited by you, not the age of the chicken.