Taking care of horses has requirements. One of them is to have a pasture that does not have trees that is toxic to horses. As they also eat so they should be away from the toxic tress as they cannot distinguish what is toxic and what is not. Let us go over what are some of the trees toxic to them.
Red Maple Trees. The dry leaves of this tree or even the wilting ones can produce gallotannins which also will produce a toxin called the pyrogallol.
Oak Trees. The acorns, young buds and leaves have in them some amount of tannins that are toxic to your horse if they eat a large amount of it.
Sycamore Maple Trees. The toxin that comes from this tree can cause atypical myopathy and that can be fatal.
Box Elder Trees. If the toxin from the above tree causes atypical myopathy, this tree toxin will cause pasture myopathy. The fatality rate is 75% to the horse. Do not let your horse eat any of the trees that are enumerated above and also below.
Chinaberry Trees. The toxins are contained in its berries. They do not fall but stay on the leaves at the winter time even if leaves already fall.
Other trees you should not let your horse get near to and eat from are Black Locust Trees, Buckeye or Horse Chesnut Trees, Black Walnut Trees, Yew Trees, Pistachio Trees, and Oleander Trees. The best thing is that do not plant them where you will put your horse.