Nineteen packing peanuts! That’s a lot. I’m glad you were able to handle those.
You can eat any chicken at any age. You might not get much meat at a young age and you will have to adjust how you cook them if they are old, but they can be cooked and eaten. Some people butcher cockerels at 12 weeks of age. They are still young enough that you can fry or grill them but there is almost no meat on them.
I prefer to wait until at least 16 weeks and prefer closer to 20. They have a lot more meat but for someone used to the chicken you buy at the store they may be too mature to fry or grill. They will have more flavor and the meat may be tough or stringy. There are a lot of different ways to properly cook an older chicken but the older they are the more moisture you need and the slower you need to cook them. You can find some recipes at the top of the meat bird section. I’m cooking an old hen today. I’ve thawed her in the fridge. She is already cut into serving pieces. I’ll rinse her off but not dry her, coat her in various herbs like oregano and basil, then cook her for about 3 hours at 250 degrees in the oven in a pretty tight baking dish so the moisture doesn’t evaporate. She will be tender and delicious although she is old. A mature rooster may go 4 hours. A 16 week old cockerel would normally go about 2-1/2 hours.
Different cockerels will develop at different rates. Some will start crowing and acting up earlier than others. There is usually a correlation to size, the bigger ones normally mature behaviorally faster. They can sometimes start crowing and get pretty noisy by 12 to 13 weeks though several may wait much longer. Normally you can reduce noise by eating the bigger ones though there are always exceptions.
I consider 30% protein feed too high for chickens I’ll keep. They’ll grow really fast on that feed but it can lead to internal organ damage, especially the liver. You can google “avian gout” if you wish. I’d personally separate them all and feed them something lower in protein, especially the pullet you are going to keep. They’ll be OK with 24% protein the first four weeks or so but after that I’d suggest nothing higher than 20% protein for the pullet. The cockerels you are going to eat should be OK at 24% and they will grow fast, but 20% works well too.
