I was thrown from a horse twice and tried to stop a runaway once when I was a boy, so I am not particularly enamored by the equine breed. But I worry about horses. I’ve been reading about plants that poison livestock and was surprised to learn that for as big and strong as horses are, they are rather fragile when it comes to eating their vegetables. Among the things that are supposed to be toxic to them are onions. Yep, says so right here in this scientific report I am reading. Also, red maple leaves, acorns, yew foliage, avocadoes (no wonder I don’t like them), hairy vetch, and many others, some of which really raise doubts in my mind, like black walnut foliage, black locust bark, and alsike clover. Alsike clover causes slobbers— excessive drooling— in horses. I sure wish my grandfather was around so I could ask him about that. He grew a lot of alsike clover because it survived on poorly drained soil and his landlord was too cheap to put in tile drainage. I remember when he still farmed with horses. Wonder what he did about slobbers?
There are many other plants that can poison farm animals. We all know that if a wild cherry limb blows down in a storm, it needs to be removed pronto from pastures because the wilted green leaves have cyanide in them in potent amounts. But I would argue that the danger to farm animals from wild plants is being overstated. Maybe red maple leaves when they are first falling from the trees in the autumn are toxic, but I’ve got red maples all over and our livestock have never been poisoned. Acorns and oak leaves? My sheep love acorns, even red oak acorns which are very bitter, and devour any little oak seedling they find. Mine have access to black walnut foliage too but have never suffered from it as far as I know. The juglone in black walnut is toxic in some ways and veterinarians say that the trees and horses don’t mix. But my neighbor’s draft horse roams all summer in a woodlot full of black walnut trees. In fact, an old remedy for internal parasites in livestock is to soak black walnut hulls in their drinking water. If you think that sounds far-fetched, a much publicized control for internal parasites in humans is black walnut tincture, made from soaking particles of black walnut hull in vodka. Think I’m kidding, don’t you. Google it.
One toxicity study describes cases where horses sickened from gnawing the bark off of black locust fence posts. And black locust foliage is supposed to be slightly toxic too. I know of several instances of cows and black locusts living together without problems, but my main argument comes from my wife’s memories. Her home farm pastures were studded with black locusts and she can’t remember of cows or horses being affected. In fact when the black locusts all died of disease (they are making a comeback now) her father was upset. He liked his black locusts. Nothing makes better firewood or a more endurng fence post.
Seems to me the first question to ask in this case is why a horse would be hungry enough to eat fence posts. I wonder in fact if the problem of toxicity in farm animals comes mostly from forcing them to graze pastures long after all the good grass is gone. They are forced to eat and over-eat toxic plants they normally would avoid.
Also, there are many examples of plants that are actually medicinal in small amounts but toxic in large amounts. Foxglove is poisonous, for example, but science has concocted a heart medicine using the digitalis in it. Poison hemlock supposedly killed Socrates, but when I noticed that my sheep would take a little nibble or two occasionally from plants that had escaped my trusty hoe, and seemed no worse for it, I decided to take a nibble myself. I can vouch that there is nothing in nature as bitter as poison hemlock. The taste alone could kill most of the philosophers I know. No animal is going to eat more than a nibble at a time unless it is starving or wants to die. I have a hunch that the occasional nibble is another way sheep control internal parasites naturally. Or maybe a nibble a day keeps the doctor away.
Anyhow, I don’t think old Socrates was very smart. If he wanted to die, why not choose a more pleasant way… like maybe a big overdose of walnut hulls and vodka.