Horse owners are being advised to look out for Ragwort in their fields or in their horses' hay.
It's a common weed that grows across the country and there's more of it than usual this year, because of the warm, humid weather.
The yellow wild flower contains toxic alkaloids that cause the liver to accumulate copper and can be fatal to horses.
Although other grazing animals are at risk, the DSPCA's Gillian Bird says young horses and ponies are most susceptible:
“If you have a horse, or any sort of equines, a donkey, or a pony in a field where the grass is not growing particularly well. One of the plants that we see growing a lot is Ragwort, it’s that very pretty yellow flower that caterpillars love but it is unfortunately very toxic to horses and can actually lead to liver failure."
“It’s an extremely dangerous plant and shouldn’t be allowed to grow on the land, and people just need to be very careful.”