By Richard Black
Environment correspondent, BBC News website
Simple changes in farming practice could stem the spread of tuberculosis in cattle, new research suggests.
Farm practice is an important factor, the study suggests
Writing in the UK scientific journal Biology Letters, researchers say herds on farms with hedges and ungrazed land are less likely to become infected.
They suspect hedges keep cattle away from badgers, which carry TB.
A government consultation on TB plans ends this week, and the researchers say it is "extraordinary" that ministers should be considering a badger cull.
"It is extraordinary based not only on my work but on the evidence they collected," said Dr Fiona Mathews, from the Wildlife Conservation Research Unit at Oxford University.
"Their own advisers have put out a report saying a cull could be counter-productive or have limited effects," she told the BBC News website, "and still it's being put forward as an option."
Betting on hedges
The main evidence on culling came from a £35m government-funded study known as the "Krebs Trial".
It concluded that culling could be effective if run intensively over large areas; but a less intensive or scattered operation could increase disease spread.
Other research has found that cattle movements are the single biggest factor in TB transmission.
The new study compares 30 randomly selected British farms that experienced TB outbreaks between 1994 and 1999 against 30 more which were disease-free.
Scientists used statistical methods to identify issues which differed between the two groups.
Not surprisingly, outbreaks were more likely where cattle on nearby farms had already contracted the disease.
But the analysis also threw up several issues of farm management, with hedges being particularly prominent.
TB was markedly less likely in farms with abundant hedgerows and ungrazed strips of land along fences; but markedly more likely where hedges had lots of gaps.
Dr Mathews calculates that "hedge-poor" farms are 60% more likely than "hedge-rich" ones to experience an outbreak.
Why hedges and ungrazed strips of land should lower TB incidence is not clear.
It may be that they keep badgers and cattle apart, preventing transmission of bacteria; alternatively it could be that either badgers or cattle living on ecologically managed farms are healthier, raising their immunity.
However, Professor Christl Donnelly, a member of the government's Independent Scientific Group on Cattle TB (ISG), cautioned against reading too much into the results. She said the Oxford team had not proven a causal link, just a correlation.
"The results are interesting, but the key thing is to realise there aren't any messages about potential disease control options coming out of this study," the Imperial College London researcher told the BBC News website.
"Habitat could influence disease transmission; but you wouldn't want to go out now and tell people to grow longer hedgerows."
Fiona Mathews agrees that more research is needed - and says the government should pay for it.
"We can't demonstrate that if farmers changed farming practices they would bring TB down," she said, "but we can demonstrate there are relationships between farming practice and TB rates, and these deserve further investigation."
This current study, which was partially funded by Defra, cost a mere £12,000.
"They spent millions each year on the Krebs trial," said Dr Mathews. "And we sat in meeting after meeting with them and asked 'what is the Plan B if culling doesn't work?'"
THE KREBS TRIAL
30 areas of the country, each 100 square km
10 culled proactively, 10 reactively, 10 not culled
Badgers culled through being caught in cage and then shot
Incidence of bovine TB measured on farms inside and outside study areas
Reactive culling suspended in 2003 after significant rise in infection
Trial cost £7m per year
She also said Defra blocked access to data gathered since the Krebs trial began - data which could have led to a firmer conclusion.
After its consultation period closes on Friday, the government will develop a strategy to address the spread of bovine TB. It now costs Britain about £90m a year, a figure which the National Farmers' Union (NFU) estimates will more than double in the next five years.
The government has received more than 10,000 submissions.
In December, the government confirmed it was considering a cull among a number of other options.
But in January, ISG chairman Sir John Bourne cautioned against culling, say it could lead to an increase in transmission.
The RSPCA and other wildlife organisations have been vocal in their opposition, while the NFU is among groups which support the idea in principle.
However, it is concerned by reports that the government is considering giving responsibility to farmers and landowners rather than managing the cull itself.
A Defra spokesman told the BBC News website: "We will use this [new research] as part of the science base when making a decision on whether to introduce a policy which allows the culling of badgers to control bovine TB in cattle in high incidence areas.
"No decisions have yet been made," he added.