During the summer, we see numerous unwanted weeds start to grow. One of these, which can cause issues for horses, is the buttercup. There are numerous types of buttercups, including the Meadow, Creeping and Bulbous species. When fresh, they are all poisonous to varying degrees, though it should be noted when dried and baled into hay, they do not pose a threat to horses.
Due to the bitter taste of buttercups, most horses will avoid eating them and instead attempt to graze the surrounding grass. However, because the weeds grow especially well on poorer quality land, when more appropriate forage is unavailable, such as on overgrazed pasture, a particularly peckish pony may decide to give buttercups a try.
The toxicity is caused by buttercups is due to an oil called protoanemonin, found in the leaves and stem of the plants. It reaches its peak concentration during the flowering period and its effects are exacerbated by wet weather. When eaten, protoanemonin causes blistering of the mouth, drooling, diarrhoea, and mild colic symptoms. The toxin can also be irritant to sensitive skin, such as on the muzzle and lower limbs.
Management and prevention of these issues is achieved by minimising the risk of exposure. Offering hay, moving horses to fresh pasture with an adequate amount of alternative forage, minimising turnout when the field is particularly wet, or eliminating buttercups altogether is recommended. Removal of the buttercups can be attempted by spraying pasture with an herbicide. Unfortunately, however, if a pasture has a particularly high number of buttercups, it may be necessary to contact a local agricultural agent who can advise on more intensive and comprehensive management of heavily infested fields.