Aesculus pavia.
Did you know this plant is highly toxic to cattle?
Yesterday something very tragic happened because we didn't know it was poisonous.

The cows were on one of the far-off lines with a bale of hay, when they busted out again (I swear they haven't for a long time, only we're weaning the babies!).  They got through the latest cow-proofing on the barn and ate all the barley--only about a bag's worth between them, so it didn't seem unusual that Mairie was not interested in eating her milking ration that day.  The next day--yesterday--I finally came out again to take some pictures of my winter garden and help Ethan milk four (yes four!!) cows, when we discovered that Mairie wouldn't stand up.  We thought at first it was bloat, but it wasn't.  I noticed her leg muscles were twitching and she was groaning a little.  Tetanus?  Low magnesium? Snake bite?
No, she could open her mouth, they've had their lick and kelp the whole time, and we couldn't find any sort of injury or bite on her.  Her eyes were not like they would be from a snake bite, either.  Even as she lay on the ground, groaning a bit, her coat looked sleek and coppery.  Her eyes and nose were clear.  She had been so healthy until this moment.
She finally stood up and walked very stiffly towards the water.  I offered her hay, which she didn't want.
She slumped over again and was groaning, and her leg muscles were twitching again.
We couldn't figure out what was wrong with her.  I called my friend Karen, where we got Mairie from, and asked her.  She had never heard of anything like it.  She called someone she knew to ask, and they said it sounded like Mairie had eaten a neurotoxic plant.

We gave her some probi, which is the only thing we could think to do.  At home, I looked up poison plants of Florida and found out about horse chestnut.  It usually is only a problem in the early springtime, because it is one of the first plants to leaf out.  It explained her groaning, leg twitches and lack of appetite and everything, particularly the strange way she was walking--not really limping or staggering, just like her legs were stiff.  And, I realized, there's a bunch of it on that line.  I had no idea it was so toxic.  For simple stomached animals like humans, it causes vomiting and severe gastric distress, but for ruminants, the toxins are converted in the rumen into a highly soluble neurotoxin.  Just a small amount can be fatal, and there is no antidote.  Mairie died this morning, and there was nothing we could do to save her.

It's amazing, with farming, how everything can seem so fine--and then suddenly something awful happens.
We are just thankful that our other cows didn't eat it, too.  We could have lost our whole herd in such a stupid way.