Originally posted by: Atheus
	
	
		
		
			Originally posted by: ICRS
I have a family member who runs a chicken farm, and according to them the chicken get "so fat their legs brake, and they can't walk". So that made me wonder about free ranged chicken. Shouldn't free ranged chicken have this problem too, and if so then what is the point of free ranged if the chicken get so fat they can't walk.
		
		
	 
Battery chickens are kept in a box only an inch or so wider than a chicken, and are force fed strange concoctions including parts of chickens and other animals, so they never get a chance to move their legs - that's why they are so weak they break. They also live in their own urine, so over time the acid begins to eat through the flesh of the broken legs, contributing to what must be serious pain for the bird, and creating the brown/yellow stain seen on the hock of a supermarket chicken.
Buy free range.
		
 
		
	 
pure bullshit.
OP, it depends on the breed of the chicken.  Through selective cross-breeding, new breeds have been established that grow big FAST.  What your relative is probably raising are Cornish-cross chickens.   They're butchered at 3 weeks of age for cornish game hens (between 2 and 2.5 pounds live weight), and can reach 8 pounds by the time they're 8 weeks old.  The cocks reach a heavier weight than the hens, hence cornish game hen (butchered early because they don't gain as quickly after that) vs cornish game cock.  The cocks are raised to the heavier weight because it's more efficient.  We tried to raise about a dozen birds to maturity so they would reproduce, and every one of them died.  Other breeders who were more knowledgeable than me who also tried reported that theirs died of congestive heart failure.  They simply grow faster than their body organs and bones can support.  None of the small breeders that I know have been successful in raising these birds to sexual maturity (and, realistically, given the size they reached, I highly doubt they'd be able to reproduce naturally.   Artificial insemination would have been required.)   In my opinion, I didn't find the meat of these birds to be as tender or as tasty as other breeds of chickens that take longer to mature.
"Cornish Cross Broiler
Our fast growing meat type bird...you can't equal them anywhere! Pullets can weigh 5.96 lbs. in 56 days. St. Run 6.74 lbs. in 56 days, Cox 7.57 lbs. in 56 days. Excellent feed conversion. " 
here
As far as feed conversion, for the crosses, it's roughly 2.5 pounds of feed per pound of weight gain by those chickens.   Thus, to have a 6 pound bird, it'd take 15 pounds of feed.  Unfortunately, feed prices have gone through the roof in the past year or so.   A 50 pound bag used to cost me under $4.85.   Now, a 50 pound bag of feed is just over $10.   ($10.15 last time I was at the feed store.)
edit:  I should have also mentioned that the cornish cross do not make good free range chickens because of their traits.   However, many people use them for free range chickens simply because they're the most available meat birds on the market.    Personally, I raise Delaware chickens to help preserve that breed.   Much slower growth weight & now a 17 months of age, they've maxed out on weight - no where near what the cornish cross chickens hit in 5 months before dropping over dead.