Housing vital to chicken welfare

By Paul Rincon
BBC News Online science staff

The chickens are very sensitive to their environment

Chickens that are commercially farmed for their meat will suffer more through bad housing conditions than through overcrowding, experts have discovered.

The European Union (EU) is planning a limit on stocking densities, but the latest study suggests other measures could improve the birds' welfare.

The moisture of the birds' litter and ventilation levels were found to be the most important factors for well-being.

Details of the research are published in the scientific journal Nature.

"If you give the birds a reasonable environment, you can mitigate some of the effects of stocking density that you might find in less good housing," Dr Marian Stamp Dawkins, a zoologist at the University of Oxford, UK, told BBC News Online.

About 70% of the UK broiler chicken industry was involved in the study, Dr Dawkins added. Ten companies in total took part, making it the biggest study of its kind.

Biggest study

As part of their participation in the study, the firms were asked to keep chickens at different stocking densities - the measure of how crowded a chicken house is - so the scientists could measure the effect of this factor on chicken welfare.

Those correlations point to further research, rather than being definite conclusions in themselves Dr Marian Dawkins, University of Oxford

The level of moisture in the birds' litter and the concentration of ammonia had a significant effect on chicken health. These factors are both related to an increased incidence of problems with the chickens' feet and legs - an important measure of their health.

Temperature fluctuations and overall humidity can also have a strong influence on the animals' welfare.

Unexpectedly, ammonia was associated with lower bird mortality, but it was also correlated with higher levels of stress hormone in the birds.

However, the research does not assess the relative importance of these environmental factors.

"Those correlations point to further research, rather than being definite conclusions in themselves," explained Dr Dawkins.

New standards

"If you do the ventilation and air circulation right then you're not compromising their well-being. To the human eye it looks very crowded, but in terms of animal well-being I don't think they're being compromised," commented Professor John Feddes, an expert in animal housing, from the University of Alberta, Canada.

But the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in the UK dismissed the conclusions of the report.

"Given that at slaughter a broiler weighs two to three kilograms, we are looking at around 23 birds crammed into a square metre in some of these sheds by the end of their lives," said RSPCA senior scientific officer Caroline Le Sueur.

"That provides less space than for battery hens."

Dr Dawkins emphasised that stocking density was still an important factor in chicken welfare.

The report found that when chickens were housed at high densities, they jostled more and also grew more slowly than animals with more space.

But more obvious measures of bird welfare - such as the number of birds that die, are culled as unfit and show leg defects - were not affected by stocking density.

Dr Dawkins describes the findings as surprising, because stocking density was always thought to be the major welfare factor for chickens.

"[The EU] had been open to the idea that stocking density might not be the only thing to look at and that you might be able to specify certain environmental factors which were also important," she told BBC News Online.

"And I'm just hoping that they're going to take that on board."