Sycamore maple
Sycamore (acer pseudoplatanus) or Norway maple (acer platanoides) are maple species whose seeds contain the toxic substance hypoglycin A. If horses ingest the toxic seeds or seedlings, symptoms of poisoning can occur, also known as atypical myopathy.
To prevent horses from eating the toxic plant parts, it is usually sufficient to supplement pasture-kept horses with hay. Where pasture growth is sparse, this prevents the intake of the “smallest feed remnants” and thereby also of the toxic seeds. It is, of course, safer if the trees are situated far enough away from the paddock. Otherwise, the only solution is to thoroughly remove the seeds and seedlings of the sycamore. Water into which the seeds have fallen also contains the toxins. In addition, maple seeds remain toxic even in hay and silage. Alongside hay feeding, an appropriate supply of selenium and vitamin E is important for horses.