Broiler Chickens

What age are the chickens most chicken-eaters in the U.S. consume?

I would have guessed six or nine months, but the answer is.... five to nine weeks. The birds have been bred to grow at three times the natural rate, eating insatiably to make that growth rate happen. According to an Australian animal rights site,

The consequences of this rapid and unnatural growth are dire for many birds. As their bodies grow too quickly, walking and even standing can become difficult due to lameness or dislocated joints. Young birds have the bodies of adults which puts enormous pressure on their hearts and immature skeletons.

Every year, around 26 million chickens [in Australia] are expected to die in sheds from illness, trauma, and starvation when, unable to support their unnatural weight, they cannot reach food and water. Most of these birds succumb to heart failure and fluid on the lungs — with these vital organs unable to keep up with their rapid growth.

The chickens, if left to live out their days, can live as long as four years.

I was not aware of this aspect of industrially farmed chickens until I saw this recent New York Times story, It could be the age of the chicken, geologically. Aside from the five- to nine-week age fact, I also learned that

There are about 23 billion chickens on Earth at any given time, at least ten times more than any other bird, forty times the number of sparrows. The second most numerous bird on the planet [has] an estimated population of 1.5 billion. The combined mass of those 23 billion chickens is greater than that of all the other birds on Earth.

And that in the slaughtering process,

most waste products (feathers, manure, blood etc.) are recycled via anaerobic digestion, incineration and rendering into edible byproducts, all technology dependent.”

The bones of the 65 billion chickens slaughtered each year, though, are not consumed, and that's where the Age of the Chicken comes in. The bones found in landfills will be part of our time's geological record, along with plastics, concrete, ceramics, and radiation from nuclear weapons and power plants. 

The Times story was inspired by a recent paper from Royal Society Open Science called The broiler chicken as a signal of a human reconfigured biosphere. From that paper, I learned in addition:

• Chickens were domesticated about 8,000 years ago, and are native to South and Southeast Asia.
• "Three companies worldwide supply 90 percent of broiler chicks and selective breeding has resulted in 50% or more of genetic diversity loss in commercial lines compared with ancestral breeds."
• The modern birds' bones are clearly distinct from their historical relatives, having much less carbon and much more nitrogen (because they are fed mostly grains, contrasted with chickens' naturally omnivorous diets).