Half of horses in the UK are overweight because owners have forgotten how to keep them healthy, leading equine vets have warned.

Experts from the British Equine Veterinary Assocation (BEVA) said obesity is the gravest threat facing horses, which is resulting in hundreds being put down every year.

David Rendle, a member of BEVA's ethics and welfare committees, said studies showed around half of all UK horses are now overweight, while research from the Royal Veterinary College found as much as 70 per cent of native pony breeds were obese.

Horses with excess weight are at risk of suffering from laminitis, a potentially fatal condition caused by blood flow restriction to the hooves, which can cause swelling and inflammation.

Around 600 horses a year are said to be euthanised as a result of the disease.

Mr Rendle warned the obesity epidemic shows no signs of slowing as horse and pony owners are now no longer capable of recognising or determining a healthy weight for their animals.

He said: "Overweight has become normal and horse owners no longer appreciate what a healthy horse should look like. Show horses are often obese, so this is what people aspire to."