The buying and selling of cattle can link individual farms to thousands of other farms, according to a new veterinary researcher-led study.
The understanding of this complex networks of ‘contact chains’ among British farms could help identify potential routes for spread of infections and improve disease control strategies in the future.
Researchers analysed patterns of buying and selling cattle on British farms, using official records of 75 million movements of cattle among farms from 2001-2015.
Starting with direct trades, when one farm buys from or sells cattle to another, the researchers traced ‘contact chains’ that describe networks of farms linked by sequential movements of their cattle.
By looking at 12-month periods of trading, the study found about half of all British cattle farms were connected to more than 1,000 other farms every year when they bought-in cattle.
And 16 per cent of farms were connected to more than 10,000 other farms in a single year.
When selling cattle, the contact chains were similarly extensive: two-thirds of farms were connected to more than 1,000 other farms.
And 15 per cent of farms again linked to more than 10,000 farms in a single year.
Helen Fielding, veterinary researcher from the University of Exeter, says: “We found that farms, even if they only bought cattle from one or two other farms, could be at the end of a chain connecting their farm and their animals to several thousand other farms.
“For example, one farm in Devon bought only six cattle in one year. Those six cattle came from four farms, and those four farms were connected in two steps back to 10 others. Tracking back 12 months, the sequence of links to the one Devon farm extended to 11,132 farms, as far afield as Kent, North Wales and Orkney.”
Prof Robbie McDonald, senior author of the study, says: “This research shows that even farms that buy their cattle very carefully might be exposed to infections from many other unknown farms across the whole country.
“Better understanding of the extensive connections formed by trading among British farms can help quantify the risks of disease spread and assist in the formulation of control strategies that work alongside efficient trading practices.”