http://www.theguardian.com/commentisfree/2015/may/19/chicken-welfare-human-health-meat?CMP=fb_gu

Inside chicken factories are scenes of cruelty practised on such a scale that they almost lose their ability to shock. Bred to grow at phenomenal speed, many birds collapse under their own weight and lie in the ammoniacal litter, acquiring burns on their feet and legs and lesions on their breasts. After slaughter they are graded. Those classified as grade A can be sold whole. The others must have parts of the body removed, as they are disfigured by bruising, burning and necrosis. The remaining sections are cut up and sold as portions. Hungry yet?

Plagues spread fast through such factories, so broiler businesses often dose their birds with antibiotics. These require prescriptions but – amazingly – the government keeps no record of how many are issued. The profligate use of antibiotics on farmsendangers human health, as it makes bacterial resistance more likely.

Nor does free range solve the feed problem: the birds are usually fed on soya, for which rainforests are wrecked