A Corn Alert

As autumn rolls on, confirmed cases of acorn poisoning increase. Sarah Smith MRCVS outlines the dangers for horses grazing in the vicinity of oak trees from her work on the toxic effects of acorn ingestion

OAK trees are an integral part of the landscape in the UK, providing shade in paddocks but also dropping acorns in the autumn.

It has long been thought that acorns may be toxic for horses and cattle. For this reason, there is a centuries-old tradition in the New Forest called pannage. Pigs are released into the forest in the autumn with two purposes: first, the pigs gain weight from eating the acorns and second, by eating the acorns, protect the New Forest ponies from any toxicity associated with acorn ingestion.

The number of acorns produced by trees varies from year to year. Depending on the acorns produced, the verderers (those who administer the law concerning the New Forest) release an appropriate number of pigs to eat the acorns and protect the ponies.

The number of cases of acorn toxicity admitted to equine hospitals also varies from year to year, with peaks seen recently in 2011 and 2013. It is likely that these correspond to years of unusually high acorn production.

Until recently, there has been little scientific evidence available about the effect of acorns on horses and ponies. The recent spikes in cases of acorn toxicity led myself and a group of vets in the south of England to describe the serious toxic effects of acorn ingestion. Our work has made vets and owners aware that clinical signs of acorn toxicity should be treated urgently — and that prevention is the best possible course of action.

TOXIC THREAT

ACORN toxicity is usually seen in the autumn, when acorns fall to the ground.