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.” Horses with excess weight are at risk of suffering from laminitisCredit:Edward Wilson / Alamy It comes after another equine vet, Joe Mackinder, told Horse and Hound magazine last year that horses admitted to his Yorkshire-based practice were getting “progressively fatter and fatter”. Dr Mark Kennedy, a senior RSPCA manager, warned horses with laminitis remained at risk even if the disease is identified and treated at an early stage.He said: “Once a horse gets laminitis once, it’s more prone to it. If a horse is overweight, it’s always at a greater risk of laminitis.”Equine vets said horses had evolved to lose weight in the winter and regain it by spring but improvements to land meant animals were still able to graze on hillsides and moorlands, halting any natural weight loss.The World Horse Welfare Association warned modern practices such as putting rugs on horses during winter in order to keep them warm had inhibited their ability to efficiently burn calories by using energy in cold weather.Experts added horse owners who treat their animals as pets often made the mistake of overfeeding, especially in the case of foals, which leads to obesity-related conditions.Sam Chubbock, from the World Horse Welfare Association, said: “Overweight horses and ponies continue to be one of the most pressing challenges facing our equine population.”We advise owners to monitor their horses’ weight regularly, using a combination of weight taping and body condition or fat scoring.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.