Hundreds of New Forest Ponies are in danger of acorn poisoning, according to forest officials. Despite a season of prolonged drought, oak trees have produced an abundance of green acorns which are toxic to ponies and cattle.

“There were hardly any acorns last year,” said Jonathan Gerrelli, New Forest head agister. “But this year the trees are loaded.”

Pigs, unaffected by green acorns, have for centuries been released into the forest in autumn to eat them up. But officials are worried that this year there will not be enough pigs to rid the forest of acorns in order to prevent unnecessary pony deaths.

Acorn poisoning causes internal bleeding in ponies and cattle followed by a slow and painful death. “The amount of acorns this year could prove a problem,” said Mr Gerrelli, “Certain ponies develop a taste for them and gorge themselves to death.”

Pannage season, when the pigs are released into the forest begins on September 23. The practice of allowing commoners, as landowners in the area, to graze their pigs in the forest stems back to medieval times.

For a fee of just £1 the commoner is permitted to graze a pig in the forest for 60 days. Last year less than 200 pigs were let out; ‘There were not many acorns so owners just didn’t feel it was worth it,’ Mr Gerrelli explained.

But this year he hopes between 300 and 400 pigs will be released into the forest. “Touch wood there haven’t been any acorn deaths so far,” he said, “but this year a lot more pigs will be needed.”