Two horses were poisoned by one of many new people using their field for exercise during the lockdown, it has been claimed.
The mares called Flossie and Merry Legs were found dead in Granby on Monday.
Flossie's owner claimed they had sweat patches and froth coming from their noses, which she felt was "indicative of poisoning".
Lisa-Michelle Hall said there has been a "massive influx" of people using the footpath in the Nottinghamshire field.
Ms Hall, from Melton Mowbray, Leicestershire, said the horses were found dead by a friend on Monday morning.
The 41-year-old said the public footpath going through the field was mainly used by children taking part in the Duke of Edinburgh's Award and "the odd walker", but recently there had been a "massive influx of people".
Ms Hall believes the horses were fed something they do not eat by a walker, "probably not intentionally".
Leicestershire HorseWatch said it has heard of several problems due to the increase in people using the countryside during the lockdown.
Shelley Page, from the group, said some footpaths had become "like the motorway all of a sudden".
She added many people do not realise the dangers of feeding horses and the vet believes it was poisoning.
Dr Sarah Upton, a senior lecturer in equine science at Nottingham Trent University, said: "The horse's digestive system is extremely sensitive and ingestion of inappropriate feedstuffs can lead to digestive upset which can be fatal."
Alan Hiscox, from The British Horse Society, said many people were "unaware of the risks certain foods or grass cuttings can pose for horses".