I am sorry this post may be long and rambly but I wanted to share our good/bad experiences with you as I was never able to find much info when I first rescued our chickens.
We have "rescued" birds as well! They are definitely NOT the same as real chickens. BUT We love ours
Our first ever chickens were rescue birds so while I knew the rescue birds were dumb, I never realized how dumb until I got 3 day old layer chicks and they were smarter than our 8-12 week old rescues ever were!
It took a LONG time for our rescues to learn to move around. (If you get them when they are only 3-4 weeks old they do better than at processing age/size). Our first white rescues were rejected so they were either too sickly or too swift to be taken for butchering, so we took them from the chicken houses. Over the last year+, we have lost the 1 here and there. The last 2 died of heart attacks (we found them laying on their back with their feet up in the air). In the beginning they were clueless and only wanted to sit and eat. I never knew you had to limit their food so they over ate for a long time. So the first thing you should do is keep food away from them!
Mine were also scared of the light. They weren't use to so much bright light.
They lacked muscles tone so they seemed like they had bad legs but they improved with time (until they hurt themselves flying). They finally learned to move, walk and run and eventually fly. I think reducing their food so I could feel breastbone not just plump meat/fat helped
It took forever to get them to go up their ramp to roost (like months and months).
They are dirty birds. Their poop is all over, yucky and stinky no matter what feed I try, etc. Some feeds do seem a bit better though.
Ours finally learned to free range and eat bugs BUT they were prone to impacted crop too. I swear they are part goat as I have found where they have been pecking my window a/c unit so it is missing plastic and God knows what else (I only found the damage while inside and haven't ventured out to check outside due to it being dark). But in the beginning they only eat feed - no grass, no bugs, just feed. But they always act like they are starving.
One thing someone never told me was that they pull their chest feathers before they start laying eggs (I thought some did this when they were broody but not just b4 laying any eggs!) So one by one my chickens pulled out their feathers and started laying HUGE brown eggs. Over time the eggs have gotten smaller (about an xlarge size).
In April (in N. GA) they couldn't stand the heat of being out in the sun and kept hiding under the greens (collards?). I was hoping they would help clean up the garden but they were too lazy, but mostly too hot.
They definitely have legs issues. They didn'tt learn to fly for a long time. Even then they don't fly higher than 2-4 feet except one of mine which had to have her wings clipped as she kept flying over to the other "baby" chickens. She liked to eat their food but also, laid her eggs in their pen/coop area. Even after clipping one side she still managed to fly in, somehow, so I clipped both wings. I dunno what her deal is as she is as these birds are huge and kept growing for months! Flying is not recommended - or even jumping as mine have slowly hurt themselves but with that said I still have several without leg issues too. It seems to just vary. And you can't just stop them from trying though you could get rid of any coops, etc.
I was told they would lay eggs as the folks who raise them for a commercial company have also rescued them and raised them for eggs. They lay great when it isn't hot, but it seems to take its toll on them quickly (though these are the only birds I have had but their legs seem very light for the length of time they have been laying).
Always remember - these birds will kill themselves. They are just so clueless. At times they would eat nothing but the calcium. Most the time they will eat the ground, all day long so that the sand I did have, is gone and there is nothing but clay. In the winter they run around more but since I put up an automatic feeder (as we aren't home everyday due to taking care of some family members) they just lay near it waiting for it to dispense food. They use to hop up and peck at it so I had to raise it higher. For 6 birds I was feeding them about a gas station plastic cup full of feed, divided up morning and night. I can't remember how many ounces that is but I think it is 32. So that would be about 16 ounces in morning, 16 at night. They love the feed but were clueless about eating fresh veggies. They like bread, seeds, and some of them like bugs or worms. They liked the collards right off the plant too.
They are dirtier than regular chickens. Their bum is always nasty (they often "roost" on the ground or a flat surface, esp. when younger).... and they get their water dirty all the time. They even had trouble figuring out their water in the beginning. I use to try an wash their bums. Even when they roost they still have dirty bums from watery poo (don't handle heat well). The other chickens are more dainty and position themselves so they don't get dirty. I had no clue there would be a difference but there is! They apparently don' t know how to be dainty chickens like my others, lol.
But with all this said - we love our meat rescue birds. I would def. rescue some when younger, but not sure about when older (like some of ours were) as those seem to be the hardest to train/untrain. If you have the heart I would cull them when younger (maybe 4-6 months if you want them really big but they may not live that long due to heart defects - not just overfeeding issues). I have yet to figure out how to integrate my rescue chickens with my 3.5 month old chickens. I have the yard separated with temporary fencing, in hopes they could integrate but I don't know how to feed the big meat (layers) their food and let the other have theirs. Sometimes the little ones get in with the big ones and I find feathers on the ground, but most times the little one is out in the grass (not near the big feeder) staying safe but panicking, wondering how to get with the 19 other chickens. But once I have found the rooster in their with the meat birds and his feathers on the ground. He managed to sleep on their coop and survive until I found him the next morning. So it seems they even pick on the roosters, lol. Since the regular chickens will never be the same size as the big meat bird, rescue chickens, I doubt they will ever get along well and since the big ones will literally eat themselves to death, I plan on keeping the flock separate until I have the time/heart to cull the meaties. They were laying eggs, even if just 1 egg a day (not one for each chicken but just 1 egg out of 4 layers due to the heat). But the last 3 days, nada.
I too have been worried about diseases as I never tested my meat birds and their poo is so nasty (and lots of it!!) unlike the other chickens. But they only have a fence between them and so far no issues that I can tell. (fingers still crossed on this one!)
Mainly - don't expect the meat bird to be like the others.
My meaties also like to eat humans! In time I have ended up bleeding as they started trying to eat us after 6-9 months of having them. After they started laying eggs they turned back into sweet birds until the first of June and they got all mean again. So they were nice for only 4-6 weeks, lol... except when they were little. But then I was always worried they would die of heat stroke, over feeding, under feeding, leg injuries, etc. But I am here to say we made it! The 5 I have left (out of 7 or 8) are still alive. 1 has never laid as she has always been too sickly, but her comb looks alot better than it did when we got her and it was so pale!! Now it is just drier and smaller than the other hens. It just takes them forever it seems to lay or learn to be chickens. Around 1 yr to lay, and many months to forage or roost. We had to teach them to eat worms
but my baby chickens took to jumping after flying insects from the first day they were big enough to go outside!
And since my other chickens are still young, I am still learning how different these rescue birds are from layers, but I will try to answer any questions you have. Just wanted to let you know it is possible, to keep them alive, even when you have never had chickens (like us!) but if I had raised chickens before, I would not have been prepared for how different they are, in my opinion.
