LONDON (Reuters) - The deaths of no fewer than four people after being trampled by cows in the past two months has prompted Britain’s main farming union to issue a warning about the dangers of provoking the normally docile animals.

A cow grazes at sunset in Leicestershire, central England October 23, 2007. REUTERS/Darren Staples

Cows can become aggressive and charge, especially when calves are present and walkers are accompanied by dogs, said the National Farmers Union (NFU).

The union and the Ramblers’ Association both advise that walkers release dogs from their leads when passing through a field of cows.

“The cattle are interested in the dog, not the walker,” said Robert Sheasby, Rural Surveyor at the NFU.

“As the cattle try to get the dog, there’s a high chance they will get the walker too.”

Britain has 7.5 million cows but in the past eight years there have only been 18 deaths involving cattle, including bulls whose dangers are well-known.

The current spate of attacks by cows began on the Pennine Hills on June 21, when Liz Crowsley, a veterinary surgeon from Warrington, was crushed against a wall and then trampled underfoot while out walking with her two dogs.

On July 15, another attack took place in Derbyshire, when Barry Pilgrim, a 65-year old from the area, was trampled to death by a cow as his wife looked on.

Three days later, Anita Hinchey, a 63-year-old, was walking her dog near Cardiff when a cow attacked her and trampled her to death.

The fourth fatal attack claimed the life of Harold Lee, a 75-year-old farmer from Burtle in the West Country. He was killed by his own herd, which may have been made nervous by the siren of a passing ambulance.

The risk is especially high in the spring when many of the calves are only a month or two old and the mothers are therefore especially protective, the NFU said.

“It’s to do with spring and autumn calving,” said Sheasby.

“In the autumn, cattle will be coming into winter housing but in spring you want them out grazing the grass.”

Cow-charging incidents received extended coverage when former Home Secretary David Blunkett was attacked by one in June as his guide dog led him across a field in England’s Peak District.

Blunkett broke a rib and was heavily bruised but survived.