If you have friends with horses in Florida please spread the word. There is a weed called Creeping Indigo that is being found all over Florida and it KILLS. Here is a picture.
The easiest way to tell them apart from harmless varieties of Indigo and other plants is that the leaves alternate. They are not lined up straight across from each other. I'm no expert as I don't live in Florida and have never seen it (and just learned that it existed), but here are some resources. If your horses have been eating it and aren't showing any signs DON'T ASSUME it is safe! It has a cumulative effect! If not treated properly (some sources say there is no treatment, but they are finding something that works) the symptoms can be permanent or the horse could die.
Here is the website for more information. http://www.ninaswarriors.com
Here is the Facebook group. https://www.facebook.com/groups/1393073010988149
Here is a map showing where it has been confirmed to be located. https://www.zeemaps.com/map?group=1414459
People have been finding it in pastures, at show grounds, camp sites and even alongside roads and in parking lots. I'm not trying to alarm people, but I really want to spread the word before more horses die. The symptoms are often misdiagnosed as EPM, etc. Please spread the word! Thanks!
P.S. Grazeonext kills it, but it has a deep tap root (up to three feet) that needs to be destroyed. It can't survive in cold weather so it hasn't be found anywhere else (so far, not confirmed anyway) except maybe in south Texas.