Sydney Morning Herald reports that animal welfare group, Voiceless, will publish tomorrow a report it says exposes cruel factory farming practices on chickens in Australia.

Selective breeding has produced broiler birds that can grow to slaughter weight almost twice as fast as they did 30 years ago. A chicken's lifespan is six to seven years but a factory farm chicken's lifespan is 35 days - and its brief life is shared with up to 60,000 chickens in one shed.

The Voiceless report, From nest to nugget: An expose of Australia's chicken factories, will be launched on 25 November by former New South Wales premier, Bob Carr. It argues that because breeding research has focused on developing muscle and fat tissue, many meat chickens have fragile legs that buckle under the animal's weight.

It argues lameness and skeletal disorders have become major welfare issues. In some cases, fast growth has affected the hearts and lungs, resulting in lethal metabolic disorders.

Last financial year, 470 million chickens were slaughtered in Australia, meeting a demand that has grown an astounding 15,000 per cent in the past 50 years.

Voiceless co-founder Brian Sherman said Australian chicken meat practices were shameful. But the Australian Chicken Meat Federation said Voiceless's claims were disappointing, inaccurate and misleading. It said Voiceless used false science and selectively quoted or misinterpreted overseas papers that were not relevant to Australian practices.

"It makes no economic sense to breed chickens that won't make it to market because they'll be lame or unable to reach feed and water," the federation's executive director, Andreas Dubs, said. "Australian chicken meat growers care about the welfare of their flocks."

Sydney Morning Herald concludes its report with comments from RSPCA Australia, which said Voiceless's concerns are valid. "Our main welfare concerns are the lack of space and the fast growth, which does lead to problems with bone disorders," RSPCA scientific officer for farm animals Melina Tensen said. "You'll go to a factory farm and find most of them sitting down."