Ask the Vet – What plants are toxic to horses?
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Ask the Vet – What plants are toxic to horses?

October 28, 2019


DAN: “What plants
are toxic to horses?” So I know in the past,
we’ve done videos about what fruits
and vegetables– DR LYDIA GRAY: Right. DAN: –which, we’ll put a link
in the description for you guys so you can check that one out. So I am curious to
see what plants are. DR LYDIA GRAY: Oh,
so the short answer is pretty much everything. There’s hundreds. And this book is quite old. It’s Horse Owner’s Field
Guide to Toxic Plants. But– DAN: The name says it all. DR LYDIA GRAY: Yeah,
it’s a wonderful book. I think I got it in either
undergrad or vet school. And I use it even now. So it’s quite old. And there’s also– so the
author, Sandra Burger, used a resource. His name is Anthony Knight. And he’s recognized as one
of the gurus of toxic plants in animals, especially horses. So great resource. And he has written
or been interviewed for many articles in magazines. And I picked one in Equus
a couple of years ago where he listed the 10 most
poisonous plants for horses. DAN: OK. DR LYDIA GRAY: OK, so I
want to read through that. And those are the ones
to keep an eye on mostly. So bracken fern– and
I can add some tips about each, like must consume
hundreds of pounds of it, which normally wouldn’t be
a problem except this is one of the few poisonous
plants that horses find tasty. DAN: Ah. Why is that? Why does nature do that? DR LYDIA GRAY: It’s not fair. So number two is poison hemlock,
where four to five pounds is a lethal dose for a horse,
and then tansy ragwort, also known as groundsel. It’s, again, in the 50 to 150
pounds, but it’s cumulative. DAN: So they would have to be
out in that area for a while. DR LYDIA GRAY: Over time. DAN: Over time consuming that. DR LYDIA GRAY: Yeah. Something in my area– Johnsongrass or sudangrass. It’s a sorghum variety,
but only when it’s damaged, wilted, trampled, frost. DAN: OK. DR LYDIA GRAY: Yeah. Like– like the red maple
leaves, which is on here too. Only a pound or two
of those can be toxic, but it has to be wilted leaves. So in the fall when the
leaves drop or after a storm. DAN: So that’s when
they’re the most toxic. DR LYDIA GRAY: Yeah. Leaves– red maple leaves
on the tree aren’t toxic. It’s after they’re– DAN: Wilted and– DR LYDIA GRAY: Wilted, yeah. Locoweed, oleander– now
that’s an ornamental. DAN: Yeah. DR LYDIA GRAY: And it only
takes 30 to 40 leaves. Another ornamental, and this one
they have a lot where I live, is yew, Japanese yew. DAN: OK. DR LYDIA GRAY: It’s a bush
planted around houses. And you’re like, how do
horses get access to that? DAN: Yeah. DR LYDIA GRAY:
Well, what happens is– and here, it’s
only a handful. Only a few leaves
can kill a horse. When people or landscapers trim
the bushes and they’re like, oh, horses and they throw it
over the fence, the clippings, and then the horses eat them. That’s– DAN: They think they’re doing
something good every time. DR LYDIA GRAY: Yeah,
that’s how it happens. So you’ve got to be careful. Water hemlock is on there,
and yellow starthistle, which is also known
as Russian knapweed. So those are my list of 10. DAN: Is there
something people can do to find out if they have
these things on their property? Because I’m a super
hypochondriac. So now you’ve told me this. I will assume everything
in the area is now toxic. DR LYDIA GRAY: So I
wrote also an article. Could you hold this one? DAN: I absolutely can. DR LYDIA GRAY: Yeah. It’s a really good
article in Dressage Today. And what’s the date on it? Can we see the month and year? DAN: 2016– March 15, 2016. DR LYDIA GRAY: OK. So this is the issue you want. And the article mentions
things about who to contact in your area
about the poisonous plants. Because poisonous
plants, like all plants, they don’t grow– most of
them– throughout the US. There are areas, like the
dry southern southwest US or in the cold
northern climates. Or maybe a plant only grows
in Florida or something. So talk to your veterinarian. And if he or she doesn’t have
the resources right there, what you’ll do is work with your
local vet school or university. And the county extension
agents are a great resource. They know exactly
what plants are in your area what to watch for. DAN: So you can see
if anything matches up to what’s on that list. And then if you have it– DR LYDIA GRAY: Yeah. The other tip is because
most poisonous plants aren’t very palatable,
horses avoid them except when they’re hungry. DAN: And then
they’ll eat anything. DR LYDIA GRAY: Well, yeah. So when I was in practice,
every July, August– so every summer, fall– we’d have an outbreak of
white snakeroot poisoning because pastures would dry up
or horses would eat them down. And then they were hungry. So they would– this
plant is found on the edge of a pasture or the woods. They would go further and
find the only growing plant, which was white snakeroot, which
ordinarily, they wouldn’t eat. But they were hungry. DAN: Yeah. DR LYDIA GRAY: So if you
can keep your pastures in good shape and
your hay in front– when pastures are not looking
good, then supplement with hay. DAN: Mmm. DR LYDIA GRAY: So
keep your horses full. DAN: So then they’re not– DR LYDIA GRAY: –seek out– DAN: –those other– DR LYDIA GRAY: –things
they normally wouldn’t eat. So– but the other
thing I wanted to tell you– so we got the
important stuff out of the way. DAN: Yes. DR LYDIA GRAY: 10 most
poisonous plants and a few tips. My husband is a
veterinarian, too. DAN: Mm-hm. DR LYDIA GRAY: You
knew that, right? DAN: Yes. DR LYDIA GRAY: And he’s
a small animal vet. And he’s interested in
snakes and toads and frogs and amphibians. So he’s what’s called a
veterinary herpetologist. DAN: Yeah, you guys have
a couple snakes, right? DR LYDIA GRAY: We do. We do. So every once in
a while, someone asks us, “Are your
snakes poisonous,” right? DAN: Uh-huh. First question to
come out of my mouth. DR LYDIA GRAY: And he reminds me
that snakes are not poisonous. Snakes are venomous. DAN: Ah. DR LYDIA GRAY: Do you
know the difference? DAN: I do not. DR LYDIA GRAY: I did not
either, and I forget. And so I am reminded
by him every year. So poisons are toxic substances
secreted by plants or animals. DAN: Mm-hm. DR LYDIA GRAY: Like, there
are those poisonous dart frogs of somewhere,
Brazil or something. OK, venom is injected. DAN: Ah. DR LYDIA GRAY: So you
have to be bitten. So there’s a little– if you bite it and
die, it’s poisonous. DAN: If you bite it and
die, it’s poisonous. DR LYDIA GRAY: If it bites you
and you die, it’s venomous. So there you go. DAN: That’s the fun
tip fact for today. DR LYDIA GRAY: Yep, yep. DAN: That’s a good
way to remember it. DR LYDIA GRAY: You need
that, who knows, tomorrow. DAN: Hopefully not.

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