Most chickens are fed a diet of grains—milled soy, corn, wheat, and micronutrients —tailored to their age and modified for different stages of growth. Many large producers add trace amounts of arsenic to their feed to ensure that chickens are getting this necessary compound. The "minimum amount" is often exceeded as an insurance policy to ensure proper growth. (Most added arsenic is "organic"—as opposed to inorganic—but some find this distinction unsatisfactory.) The arsenic in chicken feed is passed through their waste, which is composted into "natural fertilizer" or pelletized into feed for cattle, spreading arsenic through crops and other meat. Perhaps more importantly, most large producers add antibiotics to their feed to promote growth and prevent diseases. The FDA estimates that 80 percent of antibiotics intended to treat diseases that people get are used for animals.
Slaughtering and processing chickens is a sight to behold. After being stunned into unconsciousness and decapitated in the dark, they are bled, gutted, vacuumed, and defeathered. This sounds gross (and having headless carcasses move overhead on conveyors like clothes on lines between New York apartment buildings sure LOOKS gross), but if you accept the killing of animals for food, then the adoption of slaughter practices that cause immediate loss of consciousness is a good thing. (Plant worker conditions are a whole other topic.)
So is free-range/organic the answer? For some, no doubt, and I really understand the appeal. At one farm I saw an outdoor pen allowing eight square feet per chicken. It is one of the few farms certified to the highest animal welfare standards in the country. But the farmer's production cost is over $6/pound live weight. (The cost to the consumer is $9/pound). One component of his high cost is energy: He spends as much heating the night-time shelter for 300 birds as he does 9,600 birds in a house with 1.2 square feet to 1.6 square feet per bird (which also has a high animal welfare rating).
By contrast, the birds in the mid-sized operation have multiple doors and easy access to a protected grassy outdoor area with food, water, and shade to encourage their movement outside—where they actually live most days. The density stays constant as they age because the farmer grows chickens to four different weights and harvests them on different days, giving them more space as they grow. And this mid-sized farmer I visited live next door with his small children even though they could move elsewhere. That speaks volumes to me.
On the far end of the spectrum, birds on corporate farms are packed in tighter for their whole lifecycle. Researcher Nathan Pelletier, who studies animal husbandry systems, told me that confined operations may be more efficient on a per pound basis, but the confined animal feeding operations produce uniformly large-sized birds and thus may encourage overeating or higher waste, challenging the very notion of efficiency.