Did you know buttercups are poisonous to horses?
It is knowledge that I didn`t acquire until my late teenage years. I think it`s because we only had one field which had buttercups in – aptly names “Buttercup field” and it was regularly topped.
Buttercups have an acrid taste, like many poisonous plants, so are usually left untouched by horses unless they are ravenous. The bigger problem, from what I can see, is that horses grazing amongst buttercups, usually get a “buttercup burn” on their muzzle and lips. So the best thing to do is to reduce the number of buttercups in your field. If your field has a lot of tall buttercups, which hinder the grass growth, then topping is a simple and straightforward management approach.
I also discovered, in my research, that dried buttercups, such as those in hay, are safe because the toxins have degraded. Some species of buttercup are also resistant to herbicides.
To my simple mind, the best way of reducing the buttercup crop is to alkaline the soil. Buttercups thrive in acidic soil, so by applying calcium carbonate to the soil you are reducing the attraction of your paddocks to buttercups. This process is known as liming. Pastures which do not drain very well are usually prime suspects for buttercups, but short of building a complex drainage system for your farm, there is little that can be done from that aspect. Another indication of a water-logged, acidic, poor draining field is the presence of dock leaves.
Some people have found that broad leaf weedkillers are successful in killing off buttercups, but this will involve resting your paddock from three weeks after spraying, and can only be done at particular times of the year so that it is efficient.