EDIT: for some context on the problems this creates
The science is clear that fast-growing chickens like the Ross 308 are doomed by their genetics. These have been engineered to grow so incredibly fast, and their bodies just cannot handle it.”
Jackson said secret filming at broiler farms supplying big supermarkets has shown birds struggling to walk or collapsing under their own weight, or dying from heart failure, and dead birds were filmed lying among the flocks.
[...]
Andrew Knight, a professor of animal welfare and ethics at the University of Winchester, said: “With these really rapid growth rates, it can be difficult for the heart and circulatory system to keep up with the expanding body mass. A proportion of these animals suffer from heart failure. It’s also difficult for the bones, ligaments and tendons to keep up with the rapidly increasing body mass, meaning that a proportion of these birds become severely lame [inability to walk properly].”
https://www.theguardian.com/world/2022/apr/16/cheaper-than-chips-frankenchicken-at-the-centre-of-fight-for-animal-welfare
And that quote only lists just some of the health problems they face. There's a ton of other problems too
When I was in Korea, I leaned that chickens can (sort of) fly. They can flap their wings hard enough to get from the ground to a tree branch maybe 8 feet or so off the ground, and safely back down.
And I've heard chickens tasted better back in the old days. A bird that eats grubs, worms, grasshoppers, frogs, snakes, etc tastes different than one that just eats chickenfeed all day.
Wild turkeys can fly, too. It's impressive. I once came around a blind corner on my bike, there was a turkey in the road, and it took off in a manner I can only describe as 747esque --- it did not look like it should be able to fly, yet there it was, clearly flying.
My chickens can get pretty high. Only one can get a full 8ft off the ground, but they can fly pretty well for being non-flight birds. They can fly pretty far across the ground too, when they want to.
It's not just feeding them more that's caused this. To get chickens this large they genetically selected/modified for what was more profitable. I.e they may lead to features being changed unevenly
This is all at expense of pretty everything else like their health
