More on Stressed hens from ABC Radio's The World Today

A new study has cast doubt over whether free-range hens are happier and more stress-free than their caged counterparts.
Research funded by the Australian Egg Corporation has looked at the stress hormone levels in eggs produced at a dozen farms.
But the Free Range industry group has criticised the study, saying it is part of a push to change the classification of free range.
Dr Jeff Downing, from the University of Sydney, tested eggs from different farms across New South Wales over 12 weeks.
"What I found is that there was no difference between the different production systems," he said.
"But the interesting thing is there is a great deal of variation between individual farms using any particular production system.
"So it indicates to me that the challenges and the environment the hens are in on a particular farm probably has more influence on the stress levels they experience, rather than the type of production system they are in."
Dr Downing says stress levels were elevated in several situations across all three types of farms.
"This hormone is triggered by neural triggers, so the hen is challenged and the neural triggers are things like fear, anxiety, pain, and they trigger this hormone. So as these challenges increase, then the levels of this hormone increase," he said.
He says his research makes it a little more complicated for consumers to pick eggs at the supermarket.
"As a consumer, and I go and select eggs based on the production system, I don't think that gives me any guarantee that those hens have experienced less stress than those in another production system," he said.
"It's really what's happening on the individual farm that's probably more influential on the stress levels that they experience."
'Poor measure'
However RSPCA scientific officer Melina Tensen says the method used to test whether hens were stressed is flawed.
"Corticosterone is a poor measure of animal welfare. It sort of goes up and down during the day and it really depends on all sorts of things in the bird's environment," she said.
"You could see corticosterone as a level of excitement, either positive or negative, and if it's positive excitement, obviously the bird could be having fun, and if it's negative excitement, then obviously the bird is stressed.
"The overwhelming research looking at the welfare of birds in cages suggests that the hens definitely suffer in a caged environment."
The Free Range Egg and Poultry Association of Australia's president, Phil Westwood, has also cast doubts on the study.
He says the so-called free-range farms visited in Dr Downing's study were in fact not a true classification of free range.
"I don't disagree that probably the farm management has more importance than the actual production type; a well-managed farm is likely to have lower stress levels in the chooks," he said.
"But what this research doesn't show is that almost certainly the free range farms that were selected to take part in this study were actually intensive farms, so they wouldn't be farms that most consumers would regard as actually free range.
"They're running birds of maybe 20,000-30,000 birds per hectare. That is not a free range farm.
Mr Westwood says a free-range farm that meets the model code requirement has 1,500 birds per hectare.
"That allows the birds to display their normal behaviour practices. They can do the things that a chook normally does and they're not de-beaked or beak trimmed," he said.
Mr Westwood says the Egg Corporation is trying to change standards to allow 20,000 birds per hectare to be classified as free range.
Nobody from the Egg Corporation was available to talk to The World Today, however, a spokesman said the research is solid and it is unfortunate some are trying to politicise it.
A University of Sydney statement confirms Dr Downing's research received funding from the Australian Egg Corporation.
But it says he carried out his research independently and the report was reviewed by independent, external referees.