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Ep. 064: Poisonous Plant Species Horses NEED to Avoid

Co-hosts Dr. Tania Cubitt and Katy Starr chat with guest Dr. Krishona Martinson about the most common poisonous plant species to horses.

Episode Notes

On this episode, co-hosts Dr. Tania Cubitt and Katy Starr chat with guest, Dr. Krishona Martinson, Equine Extension Specialist at the University of Minnesota, to discuss how common it is for horses to consume poisonous or toxic plants, the most common toxic plant species that horses NEED to avoid - including how to identify them, how much of the plant is toxic if consumed, along with signs and symptoms to be aware of, and what next steps should be taken to help our horse if we think they may have been exposed to or have consumed a poisonous plant.


Dr. Martinson also shares some useful resources for horse owners to keep on hand to better understand a variety of toxic or harmful plant species.


Have a topic idea or feedback to share? We want to connect with you! Email


Connect with Dr. Krishona Martinson and the University of Minnesota Equine Extension Program on:


Notable References – 

~8:20 – Bell Museum of Natural History has a plant curator that is good at identify certain plant species

~1:14 – Ep. 61: The Key to Getting the Most Out of Your Horse Pasture podcast


Additional Resources – 




  • *Views and opinions expressed by guests are their own and do not necessarily reflect the view of Standlee Premium Products, LLC.*

Katy Starr (00:00:01):

Hi, I'm Katy.


Dr. Tania Cubitt (00:00:02):

And I'm Dr. Cubitt. We're going Beyond the Barn. Come join us on this journey as we bust equine and livestock nutrition myths, and interview some of the most intriguing experts in the country.


Katy Starr (00:00:15):

We'll go behind the scenes of how premium Western quality forage is grown and brought to your favorite farm and ranch retail store. We're so glad you're here. 


Welcome back to another episode of Beyond the Barn. Dr. Cubitt, thanks for being here with me today.


Dr. Tania Cubitt (00:00:33):

I'm excited to be back.


Katy Starr (00:00:35):

Yes. And today we have another guest expert joining us on the podcast, and she is a familiar voice as she's joined us on the podcast in a previous episode. She holds a bachelor's degree in agronomy from UW River Falls and a master's in PhD in agronomy from the University of Minnesota. Since 2008, she has been the Equine Extension Specialist in the Department of Animal Science at the University of Minnesota, where she was promoted to professor in 2018. She leads the University of Minnesota Extension Horse Program, which reached over 5 million horse owners and professionals in 2022 as a result of her successful efforts to incorporate technology and social media into research and extension programming. She has secured almost $2 million for her applied research program, which focuses on improving equine forage utilization and has published four book chapters, 68 journal articles, 153 abstracts and proceedings, and has advised 13 graduate students and two postdoctoral research associates. She was recently elected vice president of the Equine Science Society. Welcome back Dr. Krishona Martinson to the Beyond the Barn Podcast.


Dr. Krishona Martinson (00:01:56):

Oh, thank you for having me. And you know, you listed all of my good qualities in one fell swoop, so thank you.


Katy Starr (00:02:04):

Yes. And this was really fun for me this year, since Dr. Cubitt was off somewhere else, I had the opportunity to attend the Equine Science Society and meet you in person, which was fantastic.


Dr. Krishona Martinson (00:02:18):

Yeah, it was great to meet you as well.


Katy Starr (00:02:20):

Yeah. And so we're excited to have you on today. Before we do get started, I just want to share with our listeners that any of the topics we cover on the Beyond the Barn Podcast are more generalized and not specific to any individual horse or any specific situation. So be sure to always work with your veterinarian and nutritionist before making any drastic changes to your horse's feed program. You can always reach out to us to talk directly with Dr. Cubitt or Dr. Duren on specifics you would like to know. 


And the topic that we have you joining us today about is basically toxic plants, plant species. And I think it's also safe to say that we should also understand that there are so many toxic plants in the United States. The list that we're talking about today is most definitely not an all-inclusive list. And so you, Dr. Martinson, are going to be touching on some of the ones that are the most common. And then towards the end of this episode, we'll talk a little bit more about how to be proactive and identify the most common ones in your area because also what might be toxic for one animal may not be toxic, as toxic for another animal.


Dr. Krishona Martinson (00:03:38):

Yeah, that's absolutely true. And I'm excited to get going on this.


Katy Starr (00:03:42):

Excellent. So obviously we've heard a little bit about your background before, since you've been on here and we know about your love for horses. But can you tell us a little bit about your drive to pursue a master's in PhD in agronomy and weed science?


Dr. Krishona Martinson (00:03:59):

Yeah, sure. Well, I always tell people that this is maybe a story best told at happy hour, but in hindsight, I mean, I grew up in a very rural farming community in Wisconsin and we had a really great high school biology teacher. And fun fact my, both of my parents and I had the same high school biology teacher, he actually retired. After my freshman year. I know that that's like how, you know, you're from a small town. Right.


Katy Starr (00:04:23):

Definitely .


Dr. Krishona Martinson (00:04:24):

But we had to do something called, we had to do for our high school biology, our freshman year we had to do a Wisconsin wildflower collection where we had to collect 100 flowering plants and then memorize their common nameandtheir scientific name.And I, for some reason I dug that. I mean, I really enjoyed that and I still have my binder of all the, we had to like press them, identify them, and it turns out a lot of them are toxic plants. So I guess it just kind of piqued my interest. And I really always enjoyed biology and plant science. And so, I mean I, you guys, I didn't even know you could study weed science. It makes sense. Right. Because so much of farming is controlling weeds. But I was exposed to it in college and it just something that I enjoyed and kind of fell into. And here I am. I mean, the sad thing is horses are really susceptible to a lot of these. It doesn't happen often, but they are really susceptible to poisonous plants.


Katy Starr (00:05:26):

And do you know, do they tend to be more so than other livestock species?


Dr. Krishona Martinson (00:05:31):

Well, you know, I hate to say it, but man, I sometimes I feel like horses just, they like to die. And it's so sad, right? Like we can do everything right. But there's very few, like especially small ruminants like your goats and your sheep, they tend to tolerate plants better than horses. And really cattle can tolerate a lot of things better with just a few exceptions. So horses do tend to be a little bit more sensitive to poisonous plants compared to the other ruminant grazing species of cattle, sheep and goats.


Katy Starr (00:06:08):

What is something about weed science and toxic plant species that you wish more horse and livestock owners knew about? Kind of just like, if you could think of like a general like tip or tidbit, what do you feel like that would be?


Dr. Krishona Martinson (00:06:25):

So, and it's so hard, right? Because horse owners love horses. They really probably don't have any interest in becoming an agronomist or a plant scientist. But when you own animals, I really wish people would learn to identify the basics. So learn to identify the most common legumes, whether that's alfalfa or white clover or red clover in your area. And the most common grasses, whether that's, you know,bahiagrass or Timothy or orchard grass. Because there's really only probably a handful of those that grow and that should be in your pasture and hay. So if you have a good idea of what those look like, when there's something in your pasture hay that shouldn't be there, at least you know, hey, it shouldn't be there. It's impossible for me to know all of these, you know, potentially toxic or harmful plants. But if I know that they shouldn't be there, that cues me to try to find an expert who can help, help me determine if this is bad. Especially if I'm seeing symptoms in my animals. 


Katy Starr (00:07:27):

Right. That's actually, that's a really great one. I mean we talk about all the time Dr. Cubitt mentions all the time about, you know, taking all of these things like your horse's temperature, knowing what's like normal for your horse, their temperature and things like that. So then if something is off, something's abnormal, then, you know, so it's like completely viewing it from the same perspective. But for your pasture.


Dr. Tania Cubitt (00:07:49):

And I think last time you were on, we talked about the plant ID things on your cell phone, the apps not being very good for specifically pasture grasses, but do you, would you recommend a local extension office to probably have a list of what's more regional would be a good place to start?


Dr. Krishona Martinson (00:08:11):

Yeah. That's great. That's great advice. So anyone in your local extension office, if you have access, it sounds funny, but we have a Bell Museum of Natural History and there's actually a plant curator there that's very good at identifying things. If you have a Master Gardener, they're very good identifying or someone that's


Dr. Tania Cubitt (00:08:31):

Another good one. A Master Gardener.


Dr. Krishona Martinson (00:08:33):

Yes. Or someone that even works at your local agricultural cooperative, like where you buy seed or feed or fertilizer. A lot of times they will employ an agronomist who's good at plant ID in in your local or regional area. So those are all good suggestions.


Dr. Tania Cubitt (00:08:49):



Katy Starr (00:08:50):

Yeah, that's excellent. And how likely is it for horses to actually consume toxic plants. If they had choices, I mean, is that something that they would regularly do or what's dependent on that?


Dr. Krishona Martinson (00:09:05):

Well, you know, I never want to panic people and I don't know where that line is between preparing people and panicking people, right? So we want to prepare and not panic. You know, there are poisonous plants and trees or harmful plants and trees everywhere. But in my opinion, the amount of toxicity we see is fairly minimal. But there are some times of year and I know we're going to get to that in some areas where it becomes more common. So I would say if you have good pasture management and you're not overgrazing, and I think these are topics that you all have covered previously on the podcast, and if you are also supplementing hay during the fall or winter months when your pasture may be very sparse, you know, I think it's pretty rare.


Katy Starr (00:09:55):

Yeah, no, that's great.


Dr. Krishona Martinson (00:09:58):

But I'm open to your guys' feedback too, because I'm in a region, you know, in Minnesota and really the upper Midwest, you know, during the winter months, let's face it like nothing grows, right? We're feeding hay. And then during the summer months we tend to be, we, well we tend to have good amount of moisture and cooler weather. So we tend to have nice pastures. Now where you guys are from, you may see differences, you may be seeing more issues than what we see here in the Midwest.


Dr. Tania Cubitt (00:10:23):

I would say for me, on the east coast, from Florida to Vermont, you know, heavily horse populated areas, most of the equine community doesn't have the luxury of a lot of pasture for their horses. Maybe the pasture is more for exercise or socialization, but not necessarily for, you know, nutritional needs. I would say a lot more people rely on hay year round on the east coast. And just from my experience, that's probably where most people are going to maybe see some of these poisonous plants is in the hay. Because a lot of times the fields really don't have anything in them at all. So maybe you could touch on that. When it's in hay, it’s much harder a horse to sift it out. Am I correct there?


Dr. Krishona Martinson (00:11:27):

Yeah, Dr. Cubitt, you are 100% right in a pasture, a horse that is well fed will very unlikely purposefully graze a toxic plant because a lot of times they don't taste good, right? There's some kind of a anti quality factor that makes them just not appealing or palatable to the horse. Like you mentioned in hay, a lot of times in hay it's accidental ingestion because the horse can't sort, especially in like a large round bale, maybe in a small square bale, if it's spread out in a feeder, they can sort, but you know, the horses just can't sort as well in hay as they can kind of selectively graze in a pasture. So you are absolutely right. Most of the toxicity issues we see from poisonous plants are from hay and not pasture.


Katy Starr (00:12:16):

Well, and I also think about when, you know, it gets, you know, baled into hay and such, the weed and the plant or, and the hay is also they're both dried out and lose all that moisture. And so I, that plant structure kind of changes to where it's quite a bit more similar to the hay itself versus if it was out in the field somewhere.


Dr. Krishona Martinson (00:12:37):

Yeah. And you know, and that's true to a degree, when you get something dry in hay, you know, our hay should be about 15% moisture or less just to have good quality long-term storage. And the problem is it can get a little bit brittle. So you could have some key plant structures like leaves or flowers just kind of break off or kind of disintegrate. I mean, then it's very hard to tell. But you know, if you are feeding a mostly grass hay and you have these big broadleaf weeds in there and we know for sure they aren't a clover or an alfalfa, again, that is when knowing how to basically ID a few things in your area, that is when, again, the warning flag should go off in your mind. Hmm. This giant leafed plant in my hay is not normal, it shouldn't be there. I better have someone identify this to see what it is.


Dr. Tania Cubitt (00:13:27):

So I'm going to throw another one out there. I'm just thinking of it and thinking of personal experience and it's not on our list that we've already kind of gone over, but what about foals? My kids, I remember when they were little, Krishona, you can remember, Katy, they put everything in their mouth. They're constantly eating stuff they shouldn't. Foals seem to be quite inquisitive as well. Would you say that foals may be more likely to nibble on things that they shouldn't? If it tastes bad, they probably won't nibble again and wouldn't have an issue. But what can you tell me about, you know, foals?


Dr. Krishona Martinson (00:14:06):

You know, I think that's a great point. So in some of the poisonous plant research that we have done, especially when we have been working with seasonal pasture myopathy and the seeds of box elder trees, you have to be careful about foals or horses that tend to be, we call them more adventurous eaters. I'm sure all of you have horses with personalities where they're sort of into everything. And those tend to be younger horses and also foals have just a lighter, a smaller body weight and a lot of times, I mean, for a lot of poisonous plants there isn't a diagnostic test and we don't really know the exact toxin in the plant or how much it takes, but for some we do. And of course, if you have a smaller animal, it takes less of them nibbling and eating to have a toxic effect.


Dr. Krishona Martinson (00:14:53):

So foals, adventurous eaters, we've also seen that horses that are new to a site, so we just had a case recently where a mini, a miniature horse and a pony were gifted to atherapeutic riding center. And unfortunately, they were new. I mean, there were horses that had been there for 15 years without issue. For whatever reason, these horses we think went after some toxic plants that we’re still trying to identify exactly what they could have maybe gotten into. And simply because they were new and maybe more adventurous eaters, maybe they hadn't learned to stay away from them. They did have some fairly significant issues with those horses. So again, anybody that's new to the property, a foal, horses that you would consider more adventurous eaters are sort of into everything, are horses you would have to watch much more closely than resident horses or horses that just sort of are just more of your average type grazers or eaters.


Katy Starr (00:15:52):

That is such a great thing to bring up because if you're in an area where you have had horses and you've never had issues, you would never think bringing a new horse in, you probably, it wouldn't even cross your mind to think about that.


Dr. Krishona Martinson (00:16:06):

Yep. And we, we see that a lot with, with horses that are brought in. In fact, that is what kind of sparked some of our research into poisonous plants was that exact scenario where we've had horses on site for 15 years, you bring in two new horses and within five days those horses are deceased or are exhibiting major symptoms of a poisonous plant.


Katy Starr (00:16:27):

Okay. So, and then what are some ways that toxic plants can spread?


Dr. Krishona Martinson (00:16:33):

Oh gosh, there's so many.


Katy Starr (00:16:35):

I know there's like so many, but what are some, I guess more of the common ways?


Dr. Krishona Martinson (00:16:39):

So I know this isn't a pasture management podcast, but honestly, anytime you overgraze a pasture or have a hayfield that is maybe, you know, a lot of, especially alfalfa hayfields, sort of have a three to five year lifespan. So a pasture that is overgrazed or a hayfield that is just kind of ending its natural lifecycle. You tend to get openings in the ground. And you know what grows in those openings are weeds. They're very opportunistic plants. And some of them are toxic. So weeds can, you know, just grow from seed. Some of the seeds can remain dormant until they have an opportunity for up to 20 years. Although 85% of weed seeds do tend to germinate within the first year. But that 15% of weed seeds kind of lay dormant in the soil and wait for that opportunity. Some of them tend to float in water.


Dr. Krishona Martinson (00:17:32):

So one of the things I always tell people is if you are fortunate enough to have a stream or a pond on your property, which cosmetically is beautiful, right? There are so many toxic plants that grow in and around water. You really have to pay special attention. And look, if you have a heavily wooded pasture or an area with a lot of trees, that is another area where they grow. So, because some seeds tend to like, are buoyant in water, when you have just natural flooding and receding water cycles, we see a lot of places, plants, you know, around pond edges or stream banks or things of that nature, or where you have occasional flooding or kind of wetter soils. A lot of them kind of hang out in shady areas. These plants are shady in more than one description, right? So yeah, I mean a lot of times it's just seed. But again, they need that opportunistic opening. So either a hayfield that's nearing its just end of life or a pasture that's been overgrazed or not well maintained.


Dr. Tania Cubitt (00:18:38):

Here is another scenario for you. So I grow elderberries in my garden because I harvest the flowers. I know they're probably not a weed, a poisonous weed, but I also spray my fence lines because I hate weed eating. It's like the worst thing in the world to do. So I spray a tiny little line down the fence line. So I'm mowing the other day and I'm like, why are there elderberries growing on the fence line? Well, the birds eat the berries, they sit on the fence, they poop. And that tiny little strip that I have sprayed, nothing else is growing and these dang things are growing. So there's an, there would be another way that's so easy for these things to spread. Oh, birds and my management .


Dr. Krishona Martinson (00:19:25):

I'm so glad you said that. So a lot of, I mean, and not that it's toxic, but buckhorn is a weedy shrub that so many people, you know, struggle with. And actually it's a laxative. So when the birds eat it, it makes them, you know, defecate. So actually the plant is actually pretty smart, like around all of these flyways, there's buckthorn everywhere because the birds eat the seeds, it's a laxative and then the birds spread it everywhere. So you are 100% correct birds, other animals, and really from field to field, any kind of haying equipment, I'm sure if you've ever baled hay, you've seen all that.Just like the little plant parts that are on, you know, the baler or the rake or the hay mower. You know, just at the end when you're done with a field, just try to wipe that off the best you can. You know, have a little broom with you or something so that you don't spread those seeds going, or plant parts going into other fields as well.


Katy Starr (00:20:18):

Yeah, that's a good point. And then what would you say, I know we're going to go through a few examples here. We're going to talk about a few, but I would love to know, what would you say is probably the most common poisonous plant that you are familiar with or have the most incidences with in your work with horse owners in your region?


Dr. Krishona Martinson (00:20:41):

So there's probably two that come to mind and you can tell me how much detail you want to get into. One of them ishoary alyssumand it is one that is common in hay and it's very common in the upper Midwest and not so common where Dr. Cubitt is from, especially on the southern part of the east coast. So, and the other issue is a lot of hay from the Midwest ends up in the south or the east just because we can grow hay well here. And honestly, horses in that part of the country just haven't been exposed to hoary alyssum. So we see much more exaggerated symptoms when horses that are, that just don't have a history of having it around in their environment are exposed to it. And the other one is foxtail.Foxtail is more of a harmful plant. It's not really toxic, but we have had a few cases where, you know, the foxtail seed head had these little microscopic barbs or awns on that little seed head that makes it look like a bottle brush cleaner. Right. And those can become embedded in a horse's mouth. And we did have a horse come to our university hospital that had so many of them embedded in their mouth. It wasn't practical. I mean, it just, it wasn't an option to remove them. And the horse was so off feed and so sick that the horse did have to be euthanized. But usually it is just a physical, the mouth ulcers, and foxtail is prevalent everywhere.


Katy Starr (00:22:08):

Right. Yeah. I think everybody has had a little bit of experience with foxtail.


Dr. Krishona Martinson (00:22:14):

Oh yes.


Katy Starr (00:22:15):

Yes. It sure knows how to grow. Well, and spread itself .


Dr. Krishona Martinson (00:22:19):

It does.


Katy Starr (00:22:20):

And this question I think is gonna be one of the, the most key things for our listeners on the episode today. But if we think that our horse may have been exposed to, or have consumed to any kind of toxic plants or things like that, what should we do to be the most proactive about that situation? What next steps should we take?


Dr. Krishona Martinson (00:22:43):

So the first thing is, you know, depending on the symptoms, you need to make sure that your horse will not further injure itself or you as a person, right, it’s people, horses, and then things. You would want to call your veterinarian immediately. You would also want, if you believe it's coming from the hay or a feed source, remove them from that location immediately. You know, take them out of the pen where the round bale is, take them out of the pasture where you're suspecting it. If they're in a weedy dry lot, take them out of that dry lot and put them in a stall with nothing in there if it is safe to move the horse. I mean, I think that's what you just have to be proactive, look through the surroundings and then remove any type of contaminated feed source that you have, call your veterinarian, and then follow their directions or their advice. If it's safe, maybe take some basic, you know, temperature, respiratory, you know, kind of clinical signs to help your vet assess the situation. And then just kind of wait wherever it's safe and wait for your veterinarian to arrive.


Katy Starr (00:23:46):

Excellent. Yeah, I think that'll be great advice for anybody that does find themself in that situation. And before, Dr. Cubitt, do you have anything else that you want to add or mention before we get into some of the more common toxic plants?


Dr. Tania Cubitt (00:24:01):

No. No. because I think as we go through, we're going to chat a little bit about kind of the stage of the plant. I know we were talking about foxtail earlier and the seed head being the part that actually hurts the horse. But isn't immature foxtail plant with no seed head, does not pose any issue to the horse. Correct. Dr. Martinson?


Dr. Krishona Martinson (00:24:26):

You are absolutely correct.


Dr. Krishona Martinson (00:24:28):

It is just a seed head.


Dr. Tania Cubitt (00:24:29):

So, yeah. And I know, you know, with my cattle, we had someone brought Johnson's grass onto our property, yay. Terrible for horses and terrible for cattle if you let it go get tall or at certain times of the year. ButI'm interested in your comments as we go through on what life stage some of these may be more detrimental that, you know, maybe simply mowing your fields when topping your fields could keep those plants at bay versus having to try and spray for every weed that might pop up. So I'm interested to hear as we go along.


Katy Starr (00:25:08):

Right. Excellent. So we have these kind of broken down a little bit by signs and symptoms a bit. So the first one that we're going to talk about is nightshade berry. So Dr. Martinson, can you just briefly tell us a little bit how we identify these plants, what they look like? How much of it can be toxic if consumed?


Dr. Krishona Martinson (00:25:28):

Yeah, so the nightshade, so nightshade is actually in the tomato and potato family. So if you think about sort of what a tomato or potato leaf looks like, that's similar to what the nightshade leaf looks like. And there's many different types of nightshade, but the berries start out green and then they usually turn like reddish or purple. And if you've ever tried to like pick them out of your garden or your fence line and Dr. Cubitt, you are right. A lot of poisonous plants kind of creep in on that fence line as well. They actually will stain your hands kind of a purplish color. And the Native Americans did use that as like a dye. That's one of the ways people think that it was maybe a beneficial, you know, plant at one time was just for dying. But we don't, we don't know a whole lot about the details of this one. And I think that's what upsets people is sometimes we don't know what the toxic agent is or how much of it is a toxic dose, but we think that less than 1% for eastern black nightshade berries is known to produce toxicosis or even death. So that would be three to seven pounds of berries per thousand pound horse. So it's kind of a lot like, I can't believe those berries would be like appetizing in any way just by looking at them. But it is a relatively small amount.


Katy Starr (00:27:01):

Right. Okay. No, that, and that's good to know. One of the signs and symptoms of nightshade can be colic. Are there any other signs and symptoms that we should look for in our horses?


Dr. Krishona Martinson (00:27:11):

You know, that's probably the biggest one. You know, reduced appetite, colic, diarrhea, and then rarely death is usually what we see with the nightshade berries.


Dr. Tania Cubitt (00:27:25):

Speaking from experience as a child, I ate nightshade berries. I had to spend a night in the hospital. I got my stomach pumped, but I was just very little. I don't think I ate that many. But anyway, I live to tell the tale that is wild.


Katy Starr (00:27:40):

It is. Wow. It's super crazy.


Dr. Tania Cubitt (00:27:43):

I did live in the outback.


Katy Starr (00:27:45):

Well that's true.


Dr. Krishona Martinson (00:27:46):

I'm so glad they got that. I'm so glad that you, that they addressed it.


Katy Starr (00:27:52):

Well and as kids like, I mean we were kind of briefly talking about this before, like kids are so curious. We have like, I don't even know what it is, some kind of bush that grows kind of in our lawn and the, my girls love, they love collecting in their buckets. Like they make, you know, food. Like I'm quoting food, like outdoor food. Nobody really eats it. And they always collect these little berries that grow on it every year. And it was always my fear when they were little. Don't you put that on your mouth? That's not a blueberry .


Dr. Krishona Martinson (00:28:21):

Yeah. I mean, you, you never know. But I do think that, you know, especially a nightshade, Dr. Cubit, you are right. That, you know, it's kind of one that can grow in like a dry lot or an overgrown dry lot or really it's a fence line. It is a fence line weed that we commonly see.


Katy Starr (00:28:38):

Yeah. With the berries and the birds. Yeah, that would make a lot of sense. And then how about mustard seeds? Because that's kind of colic can kind of come up with that one as well. 


Dr. Krishona Martinson (00:28:51):

Yeah. And that really has the same symptoms that you would see as the nightshade berries. So again, mustards have many, many different kinds of plants, you know, like yellow mustard, common mustard, there's a plethora of them. And the cool, the, not the, well, maybe the cool thing from a weed science perspective, right, is that these mustards, we call them fast plants. And if you ever did like experiments in high school biology class with fast plants, you probably use some kind of a mustard. They, you really go from seed to seed in 30 days. So their reproductive cycle is really quick. So you see them early in the spring and late in the fall in places where you have distinct seasons like Minnesota. Because of that, they're common in new seeding pastures, new seeding hay and oats, which obviously, you know, are used in many, many things.


Dr. Krishona Martinson (00:29:40):

With the mustard seeds, we really see the same symptoms, especially diarrhea, colic type symptoms. But we think as little as 0.25% of a horse's body weight is what they would need to eat, you know, to kind of have that colic or diarrhea. And again, a lot of times what we see is if horse owners that are still feeding kind of whole oats in the diet and maybe are growing their own and aren't having the oats clean or maybe buying oats from a friend or a neighbor and those oats aren't being cleaned or blown, that is where we see it a lot. And we have had a few cases where I've helped in some larger dairies that were chopping new seeding alfalfa, which is a common practice. And it just had so many mustard seeds that the dairy cattle were having, you know, quite a bit of diarrhea type problems. So it's just, it's something we see. It usually isn't deadly, but it does lead to some very concerning, you know, symptoms and in horses.


Katy Starr (00:30:40):

Right. Okay. And then how about green acorns?


Dr. Krishona Martinson (00:30:45):

Oh, green acorns. This is, this is when we get all the time. So oddly enough, I mean, you guys, oak trees are beautiful, right? You would never want to remove them from your property. But we, especially this summer months, it's common to have strong thunderstorms or wind events come through. And sometimes you can knock down a substantial amount of green acorns. We don't really know how many it takes, but we're thinking like a five gallon bucket. So you have to have a lot of green acorns that happen to fall at the right time. Really, we don't see the issue with mature or brown acorns, but green acorns, we tend to see that colic, you know, type response in horses as well. But again, it takes a lot and it kind of has to be a specific example where you have a heavily oak Savannah type pasture and you have a big windstorm come through at that green acorn stage that knocks them all down.


Katy Starr (00:31:37):

Okay. And then moving into another sign or symptom that has a, has a couple of them, you actually mentioned one of them already, but we can dive a little bit deeper into it for stocking up and founder, hoary alyssum.


Dr. Krishona Martinson (00:31:53):

Oh yes. So hoary alyssum, like I would say in the upper Midwest, it is the most common toxic plant that we have. So hoary alyssum is kind of a greenish, grayish, spindly looking plant with white flowers and it grows everywhere and it loves drought. And there's been a lot of places in the US that have been impacted by drought recently and it likes sandy soils and it is literally everywhere. When horses eat it, you'll see a stocking up or swelling usually of their back legs. But the kicker with this is not all horses will, are really impacted by it. Only about 75% of horses from our best guess, are impacted and we're unsure why. W don't know the toxic agent within the plant. There's been a couple studies, but we haven't been able to find out really what it is. And that is the one where horses will, we've never act, I've, well I have never seen an issue in the pasture.


Dr. Krishona Martinson (00:32:49):

It is always an issue in hay. So the horses just can't sort it out of the hay. They eat it, you'll see these swollen back legs, they don't want to move. But usually if you remove the contaminated hay source, within about 48 hours, most horses will recover, usually without assistance. Maybe some pain management with your veterinarian, but they usually recover fairly well. But the biggest issues that we have seen is when we have Midwestern hay shipped to Florida, shipped to other parts of the country that don't have a history of hoary alyssum and their horses are naive to it. There was a several years ago, there was a large very, you know, they're always expensive horses, right. That are impacted by these things for some reason. And they had an entire barn go down.


Dr. Krishona Martinson (00:33:43):

And some of the horses did because they were down then they get secondary issues from being down. And sometimes that swelling can kind of progress to laminitis, especially if the horses are put under stress. So the barn had all of these horses with swollen limbs, they put them on the trailer, which was a stress event. And then that did lead to some laminitis. So withhoary alyssum,it's easier to see the plant in hay because you'll see these little tiny round seed pods that sometimes are iridescent and you can see the little black individual seeds, but it's a grayish green and the white flowers. But it is best not to haul the horses, have the veterinarian come to you if you're in an area where you have an ambulatory veterinarian. But a lot of times it's just taking that contaminated hay and getting rid of it. Hoary alyssumonly impacts horses so the hay can be fed to cattle, sheep, goats, just not horses.


Katy Starr (00:34:41):

That is interesting. And I know you said that there was a little bit of research done, but there's still kind of some unknowns of surrounding it. But I wonder if it is more, it more commonly impacts those horses that kind of are newly exposed to it versus ones that maybe have been around it a while or potentially would the age, breed or anything, have you seen anything lead to possibly one of those factors?


Dr. Krishona Martinson (00:35:07):

Yeah, so some of the research has looked at gender, age, and breed. And they really, and every nothing has been conclusive, unfortunately. And so it's so hard, right? because you want some answers. And we used to say that you could actually feed hay containing up to 10%hoary alyssumto horses. But we have actually adjusted that recommendation because some horses react so severely, we now say there is a zero acceptability forhoary alyssumand horse, and hay intended for horses.


Katy Starr (00:35:38):

Interesting. Okay. Yeah.


Dr. Krishona Martinson (00:35:39):

So I don't know Dr. Cubitt, if you've ever had any experience with that in your area or have gotten contaminated hay in your area?


Dr. Tania Cubitt (00:35:46):

It's mainly been questions fielded from consumers who have purchased hay from the west and or know somebody that, you know, got hay from the West. So no, I don't see that particular weeded here often or in hay that has grown here. But certainly I have a lot of clients that are buying hay from the West. Maybe they go with their friends and they get a tractor trailer load because the hay in the west is really great quality. And so that's mainly where the question arises for me.


Dr. Krishona Martinson (00:36:19):

Yeah. And I would just really encourage anyone buying hay, especially from the upper Midwest, you know, you just try to have a good relationship with whoever you're buying that hay from. And I know sometimes it's coming through a broker and you can't get those answers, but man, just try your best to get pictures and, you know, have a relationship and maybe you've gotten hay from them before. It's just like, you know, in the upper Midwest we're fairly lucky. We rarely have to import hay, but sometimes we do from like down south and not that it's a poisonous plant, but we have the same thing with blister beetles. You just have to inspect when hay is coming from outside your local area, your region, because you just never know what other little contaminants are kind of along for the ride.


Katy Starr (00:37:03):

Right. Another one that I know I've heard a lot from horse owners always asking questions about this is black walnut shavings.


Dr. Krishona Martinson (00:37:12):



Katy Starr (00:37:13):

They wonder is it just the shavings?


Dr. Krishona Martinson (00:37:16):

Yes. It's just the shavings. And you know, it's funny, it is really the inner heartwood. So if you have a black walnut tree and black walnut trees are very valuable for their woodworking and cabinetry and all the ways black walnut wood is used. So the tree itself, there's maybe some concerns as the leaves are coming out and some of those black walnuts are kind of immature, but it's really the inner heartwood. So unless your horse is like a beaver and like totally gnawing the tree to death and standing on the little gnawing parts of the shavings, it's really a non-issue. The biggest issue is a lot of times horse owners will want to get free shavings and I am all about free stuff owning livestock. But if you're getting shavings from a cabinet manufacturer or anywhere where they're doing a lot of woodworking and the shavings are dark in color, it's probably a decent chance it is black walnut. And when the horses stand on it, and we don't even know the toxic agent, but they do have that stocking up or laminitis type symptoms. So whatever's in the black walnut, and again, we don't know, when the horses stand on it, it goes up to their feet and causes issues.


Dr. Tania Cubitt (00:38:29):

So just so it's more of a contact, they're not eating it.


Katy Starr (00:38:34):

It's kind of crazy.


Dr. Krishona Martinson (00:38:36):

Yeah. Yep. So just, just stick to your pine shavings people. That's all we gotta say , right? Or like whatever light color shavings you have.


Katy Starr (00:38:44):

Better safe than sorry for sure. Yeah. Okay, next one we're going into is, let's talk a little bit about white snakeroot.


Dr. Krishona Martinson (00:38:55):

Oh, white snakeroot is kind of a fun one. That is one that grows, it has to be shaded. I mean, it kind of has a triangular leaf and also a white flower. And I'm here to tell you, white flowers tend to never be good when it comes to poisonous plants. But again, it's not going to grow in the wide open, sunny, it needs some shade. And what we see with white snakeroot is a very distinctive symptom that the horses have red or brown urine. And it's sort of a kind of thicker looking, if that makes any sense. So you'll know like, okay, if you watch your horse urinate, you'll be, that is not right in any way, shape or form. So it produces this dark red, brown, thicker urine.


Katy Starr (00:39:43):

Okay. Sorry. There's a crop duster flying over me. . I was like, they're all over. I have alfalfa being swathed across the street and I’ve got crop dusters flying overhead. So it's exciting today.


Dr. Krishona Martinson (00:39:57):

I didn't hear anything if that helps you.


Katy Starr (00:39:58):

Oh, hey, that's good. So, is there any kind of level of toxicity with that one?


Dr. Krishona Martinson (00:40:08):

So it, it's interesting. So we do know that tremetol is the toxin that produces the effect in horses. And we don't really know the amount in horses, but in cattle it's five to 10% of their body weight over several days. So we know that it, you know, it's not going to be an instant onset of issues, but they're having to eat it, you know, kind of, I mean five to 10% of their body weight's kind of a lot, over multiple days. So that is something where you really need to watch, what is the quality of your pasture? Are you supplementing enough hay? Why are the horses actively seeking out something they wouldn't? And we do know that white snakeroot is an issue when it's in pasture and also in hay. So if you happen to have a hay field that is along the side of a woods and you see this white flower, try not to cut that and bale that into your hay.


Katy Starr (00:41:04):

Excellent. And then another, I know super common one that people ask about wilted maple leaves. 


Dr. Krishona Martinson (00:41:10):

Yeah. Yeah. So this one is so common, right? Because maple leaves or maple trees are like everywhere in our world, but it's only the wilted ones. So again, we don't really know how much or the toxin per se, but obviously in the fall, if you live in a area where you have distinct seasons in the leaves shed and they fall, that is when you have it. Or if you have a large storm that rolls through, and I don't know why, but I have watched my horses like try to eat leaves and I'm like, stop doing that. . Right? . But I don't know why. But we do think it's maybe one and a half to three pounds of dried leaves per thousand pounds of horse body weight, but dried leaves weigh like nothing. Right. So they're eating a lot of them. So again, that is a case where you would want to, what is your pasture management? Are you supplementing enough hay? It's in the fall, maybe it's time to take them off pasture and transition them slowly to a hay diet for the winter months. Right. Like, let's look at our environment and see.


Katy Starr (00:42:13):

And it's only the wilted ones, huh?


Dr. Krishona Martinson (00:42:15):

Just the wilted ones. Yep. So if you're on a trail ride or your horses are half giraffe, like mine tend to be and try to reach up and you know, and snag a fresh leaf here and there, don't panic. But if they are consuming, I mean a significant amount of wilted leaves, that's when we have to be concerned.


Katy Starr (00:42:34):

Okay. And signs and symptoms. So that would also be kind of like the red or brown urine. Is there anything else associated with that?


Dr. Krishona Martinson (00:42:41):

Nope, but that's the main one that's, yeah. And it's because there's been some red cell damage, red blood cell damage. And that's why I think you're getting that off color in their urine.


Katy Starr (00:42:51):

Okay. And another one that we hear about quite a bit, people ask if it's okay or not, is a buttercup.


Dr. Krishona Martinson (00:42:59):

Yeah. So buttercup is another one that, you know, it's kind of more of a contact, right? It leads to those mouth blisters. So there's a few plants that can cause mouth blisters. So foxtail that we touched based on, and then buttercup. And buttercup likes to grow in kind of shady wet areas, but this one has a yellow flower. So if you guys Google these, again, if you have shade or wet areas, you know, you should probably know what buttercup looks like. So again, it is that yellow flower, it does like to grow kind of where it can have wetter roots and there's a couple different types of buttercup. Tall and small flower are the ones that are most commonly seen.


Katy Starr (00:43:43):

Okay. And so you said contact, so does that mean like, let's say that they're in a pasture and there's some buttercup cups around, maybe they're not even trying to eat the buttercups, but they're trying to get to some of the other grasses that are in there, but they're rubbing up against it. Would that possibly also give them mouth blisters?


Dr. Krishona Martinson (00:43:59):

Well, so I have to correct myself. I misspoke just a tad. It can be both. But it is primarily when it is eaten fresh in pasture.


Katy Starr (00:44:09):

Okay. Yes. And I've heard that it has kind of, I mean a lot of these I guess do, but they have kind of an off taste anyway, so most horses don't want to eat them, but there are some that kind of get a hankerin for them.


Dr. Krishona Martinson (00:44:21):

Yeah. So I, you know, again, it's those adventurous eaters, maybe those younger horses that tend to kind of be into things, you know, those foals. So yes. Like I've never tried to eat these things, right. , I mean, I'm not Dr. Cubitt, maybe we should just, you know, have medical on alert. Yeah. I'm kidding. Do not.


Katy Starr (00:44:40):

Don't do that .


Dr. Krishona Martinson (00:44:42):

But you know, a lot of these plants, they don't even look appealing, right? Like this buttercup is kind of stemmy with kind of more fleshy type leaves and sometimes there's small little hairs on them, which again, I just can't imagine would be appeasing or inviting to a horse. But the good thing with buttercup is that when it is dried, it is not normally toxic. So it is a plant that is just an issue when it is grazed fresh in the pasture.


Katy Starr (00:45:12):

That is interesting. That's a little bit different from everything else we've been talking about.


Dr. Tania Cubitt (00:45:14):

Yeah. And I would say in my area here in Virginia in the spring when the grasses are, you know, everything's just starting to come on. The buttercup is the first thing that pops up and it's so pretty because there are just massive fields of buttercups. People letting their horses out slowly.


Dr. Tania Cubitt (00:45:35):

And so I would say that where I am, it's probably quite common. My friend who lives up the road, I'm always texting her, your dad needs to mow the fields. There's too many buttercups, , . And so I mean we're, we kind of run it that in the springtime people are nervous about letting their horses out with the spring grass anyway. So, we do have a lot of buttercups here. 


Dr. Krishona Martinson (00:45:58):

Yeah. And you know, some of the clinical signs is that blistering of the mouth, but you can also have blistering in the digestive system, which obviously we can't see. But the horse can have terrible like seizure type or you know, kind of colic type symptoms. But what you maybe see is kind of swelling of the nose, lips, and face. When they do come into contact with it.


Dr. Krishona Martinson (00:46:20):

So you'll see people, 


Dr. Tania Cubitt (00:46:23):

It’s a little waxy too. Yes. I picked the flowers and they're a little waxy.


Dr. Krishona Martinson (00:46:27):

It is waxy. And so again, I can't imagine that would be appealing for a horse to eat. But you know, I guess I'm not a horse and I'm not an adventurous horse. Right. . So I don't know.


Katy Starr (00:46:37):

Maybe if their palate’s messed up, they're just like, oh, what's this ?


Dr. Krishona Martinson (00:46:41):

I know. Or you know, like Dr. Cubitt said it's the only thing out there and they just have to eat it and it's early in the spring and they've been so sick of being on hay all winter long. Anything green looks appealing at that point.


Katy Starr (00:46:55):

Right. Okay. And you already touched on this a little bit, but is there anything else, since we're talking about mouth blisters, is there anything else that you'd like to talk about about foxtail?


Dr. Krishona Martinson (00:47:05):

Yep. And I just want to reiterate that it is only the seed head and that it is just the leaf blades itself. That is not an issue because it's not a true toxicity. It's more of a physical, you know, those awns become embedded in the soft palate, which causes ulcers and causes a horse to go off a feed. We do kind of, I mean you guys sometimes, especially if your area's having drought, it is so hard to have hay that has no foxtail. So we can go up to maybe 10% seed heads in your hay, but definitely not more than that. And you'd have to keep a close eye on it. because I get it, like sometimes it's your only option. You're in an area where there's drought, this is the best hay, it's got a little foxtail, just keep an eye on them. Right. But no more than 10%. So that means if you grab a handful of stems and lay out a hundred, less than 10 should be foxtail seat heads.


Katy Starr (00:47:57):

That's a good one. Going into, let's see, photosensitivity, , we have wild parsnip.


Dr. Krishona Martinson (00:48:07):

Ugh. Do you guys have wild parsnip? If you don't, you're super lucky.


Dr. Tania Cubitt (00:48:11):

Is that the one that people touch and it kind of makes it like burns your skin? We went to Vermont several years ago and Maine and it was there because I have something else. We call it queen ann's lace. And it is not wild parsnip, but it looks the same. And I'm always like, oh my God, don't touch it. But then when we went on that trip to Vermont and Maine where it's a little cooler, a little wetter and people were, don't touch that, it's going to burn your skin.


Dr. Krishona Martinson (00:48:42):

Yes. So, you know, wild Parsnip is one that it has a yellow umbel flower, so umbel, think of umbrella. So that big kind of pretty, the flower is shaped like an umbrella, but it's yellow. In the Midwest it has taken over all of the ditches on all the major highways and interstates. And a lot of times, especially when you get to the western part of Minnesota, or as you kind of go west, you know, a lot of forage comes from the right of ways or the roads or the ditches, however you want to say it. And a lot of cattle and horses are fed what we call ditch hay. And I'm sorry if that's kind of harsh, but it's hay harvested from the ditches and we no longer really recommend horses being fed ditch hay because of the prevalence of wild parsnips.


Dr. Krishona Martinson (00:49:34):

So again, it has a very lacy looking leaf with a big beautiful yellow umbel flower. But this one is also contact. So if your horse rubs against it, if you are out there trying to pull it out of your ditch or pasture and you have it and you get it on your skin and then your skin is exposed to UV light, you'll have severe burns. I mean, if you Google, you know, wild parsnip human, wild parsnip horse, you'll see some pretty graphic human, you know, just boils and blisters on their skin. A lot of times on a horse, especially a horse with a white blaze or a light colored horse like a palomino or a paint horse on their white skin, people will call and say, I think my horse has acne. Well, horses don't get acne. But that you're seeing that photosensitivity from exposure to sun. So the interesting thing is, if you have been exposed to it or your horse has been, if you keep them in the barn, they'll have less symptoms because they aren't directly exposed to UV sunlight. But you still have to have the horse looked at because there are internal things that can also happen. It is just not that external symptoms that we see.


Katy Starr (00:50:49):

Right now that you've been describing it. I think there's some in Idaho, but I, it's like where I'm at, I don't personally see it, but I remember us taking, we took a family trip to Alaska last fall and my daughter and husband went with our friends to go ride around on the four-wheeler and stuff. And I remember them telling her, because she told me, she's like, mom, you can't touch, you cannot touch that. And I was like, oh my gosh, that's exactly what you're describing right now. I was like, that was probably what it was. .


Dr. Krishona Martinson (00:51:16):

Yeah. It's really common. And it doesn't like to be disturbed. So it's not going to be in like a row crop field or a managed hay field or a well-managed pasture, but like a ditch that is maybe just cut for hay once a year. Yeah. Or a right of way. Or even again those dang fence lines. You know, that's where it'll kind of grow in and you rub against it and you'll see some of those symptoms. 


Dr. Krishona Martinson (00:51:39):

We actually used to think that it wasn't an issue when dried in hay. Oh. But it is because we have a lot of cases in Minnesota where we find it in the dead of winter, you know, in January and February when there are no pastures and we see horses with photosensitivity and we can find, you know, the wild parsnip in their hay. So it is an issue and that's almost always the issue.


Dr. Krishona Martinson (00:52:03):

It's wild parsnip in the hay and I believe there is a research paper out of Canada, I think, where they actually had a case described where they saw it, they saw it in rabbits being fed hay. So again, we do know there isn't exact research in horses, but we've seen it and then there's the rabbit research paper that kind of confirms our suspicion.


Katy Starr (00:52:25):

Okay. Interesting. Now we have a few different clovers that can cause some different symptoms. So maybe you can talk to us a little bit about the different clovers and what we might see with those.


Dr. Krishona Martinson (00:52:39):

Oh, so I mean this is such a hard one, right? Because in general, clovers are a very beneficial feed in general, a very beneficial forage for horses. So I don't want people to think they have to go out and you know, completely get rid of all of their clovers. This is something where you have to sort of look for some specific things. So probably the biggest one, I mean I think we've all heard of slobbers, right? So slobbers is actually found primarily on red clover. There's some debate if it can be found in other clover species that we know it's for sure in red clover. And it's actually not the clover itself, but it is a mold that forms on the clover. And then when that hay is harvested and the horses eat it, they will salivate like buckets full in one day.


Dr. Krishona Martinson (00:53:33):

And obviously the biggest call we get is my horse has rabies. So when you know, like that is why poisonous plants, a lot of these symptoms can be caused by numerous things. So you have to have evidence of ingestion, you have to have the symptoms. And ideally we'd have a diagnostic test that could help confirm, but of course we don't always have that. So again, red clover isn't necessarily bad, but it, when it has this mold on it and the mold really likes humid environments. So Katy, where you are, I know it can be really humid.


Katy Starr (00:54:07):

Well, in Idaho it's not humid at all. We're really, really good. But yeah, I was wondering though, I was like that with the mold, it probably would be kind of like humidity would create that mold, I would assume. 


Dr. Krishona Martinson (00:54:20):

Yeah. So Dr. Cubitt, that's probably more, I mean, you guys have a ton of humidity on the east coast.


Dr. Tania Cubitt (00:54:27):

We do. We have a lot of humidity right now. I mean I, I actually did, I grew clover, I got it seeded in my fields for my cows. But the clover really comes most, like right now in the middle of summer, I don't see a lot of clover and flowers out there, mainly because my cows are grazing it down, and it is humid, but it also hasn't rained a lot, so where, you know, the grass is actually pretty dry. I would say in the spring and the fall when that clover is a little bit more predominant and we've got more moisture in the air and in the ground as well, allowing that mold to grow, would be when we see it the most.


Dr. Krishona Martinson (00:55:13):

Well and clover likes to grow and really dense patches, so sometimes it makes us a little microclimate where it just kind of retains all the moisture and it gets humid. But, you know, slobbers doesn't really hurt a horse. Although if you're like, I'll never forget I was at a show, I used to do more pleasure oriented things, now I do speed events, but if you have showmanship and your horse is excessively salivating, I mean it is so embarrassing and it's impossible to keep clean. Right? Like you are not clean. Your horse is not clean. People think your horse has rabies. It's just a hot mess. . So it doesn't really hurt the horse, but you do have to make sure they always have access to clean and cool water so they don't become dehydrated. And usually once you figure out the hay source and remove that red clover hay source from the horse, the slobbers will kind of resolve itself within a few days.


Katy Starr (00:56:04):

And so, and then there's some other sweet clover that can cause bleeding.


Dr. Krishona Martinson (00:56:10):

Yeah. So


Katy Starr (00:56:10):

If it's moldy, I should say.


Dr. Krishona Martinson (00:56:13):

So a few other things, and again, it all has to do with mold. So with the slobbers, it is not like the forge isn't moldy, it's a little mold that grows on the clover when it's in pasture, when it's upright, when it's growing. The sweet clovers, that is when, when they are baled a little too wet and there's a product in them when it molds called coumarol. And if you've heard about coumarol or dicoumarol, all those are kind of blood thinners. So when it, when horses, if they eat moldy sweet clover, they could bleed because that coumarol is converted to dicoumarol during the molding process. But it does clear the horse's body fairly quickly. So sometimes if a horse gets a cut or sometimes you might see some blood out of their nose. And if you are feeding those sweet clovers, it is something to be concerned about. But again, white and yellow sweet clover, it looks very similar to alfalfa, but it tends to get taller. And it isn't a legume that is commonly planted. But again, it's also commonly found in roadside ditches. So it is something just to be concerned of when you have ditch hay.


Katy Starr (00:57:28):

Okay. Yeah. And, and we should probably, I know that you've said this, but just make sure people understand it's not the clover itself, but it's the ones that are infected with, with mold that Dr. Martinson is talking about.


Dr. Krishona Martinson (00:57:42):

So again, the slobbers and then even there are some molds. It's called black blotch disease on some of the clovers that causes photosensitivity. Those are little molds. And if you look on the leaves you'll find little black or kind of rust-colored dots, almost like somebody took a Sharpie pen and just put little dots on them. And again, I mean you guys, it's so common, right? And you just have to watch for it. Where with the sweet clover, it is actually baled too wet and then it kind of gets moldy in the bale, the horses eat it. And that's when we see the bleeding issues.


Katy Starr (00:58:15):



Dr. Krishona Martinson (00:58:16):

So again, these aren't things that you know are going to cause death most likely, but just things that cause horse owners to be very concerned about and you want to know what's causing it so you can correct it and not have it continue to happen. 


Katy Starr (00:58:30):

Right. And before we get to our last few, there is one I wanted to throw in and ask you about Dr. Martinson was not that it's a toxic weed, but since we're on the subject of what we're talking about, grass clippings, why is that a concern if horses consume grass clippings?


Dr. Krishona Martinson (00:58:53):

Yeah, so Dr. Cubitt, you can probably chime in here as well. So grass clippings, there's a few issues with grass clippings. It's not that they're toxic. The problem is when horses are grazing in a pasture, they have to tear the grass off. They have to chew it, right? They have to digest it. When you're feeding them the grass clippings, they can consume it so quickly. So there's an issue with choke and maybe just overwhelming their system. The other issue is if you have, I mean if you think about cutting your lawn, it's like 85% moisture. It's gonna sit in this pile. You can get some pretty quick heating and molding in that pile. And sometimes you just get some mold formation in that pile of grass clippings before the horses are eating it. So we just, it's just not a good, it's not a good practice to ever feed grass clippings to your horse. But Dr. Cubitt save me. Contribute more to that.


Dr. Tania Cubitt (00:59:52):

No, I think that's perfect. Certainly I think, you know, one of the things people probably don't think about is the rapid consumption and it can cause them to choke. because it is pretty tasty. The other thing is, like you mentioned, it's 80% moisture and we usually dump it in a pile and it can ferment really quickly. Potentially, there are other kind of small animals or bugs or things that could get into it and botulism is another issue. But yeah, certainly not a great thing to do. Also, a lot of that grass being so short, if it's a lawn grass as well, the thing that makes lawn grasses or any grasses super strong is your ability to store sugar. So when we cut that lawn grass and it is short and actively growing, I think it's full of sugar and you dump that in, that's also going to make it ferment more quickly. And for a horse that should not be eating a lot of that sugary grass anyway, you've just given them kind of a bolus of sweet grass. So for a number of different reasons, don't feed your horse grass clippings, use it as compost somewhere else.


Katy Starr (01:01:04):

Right? Yes.


Dr. Krishona Martinson (01:01:05):

Yep. And, and to just to contribute to that, you know, we have had, and I we're getting to the, or we're getting to our last category, unfortunately the plants that cause death, right? So maybe this is a good segue. You know, a lot of plants that cause death tend to be more ornamental in nature. Especially something like common yew, that is kind of an evergreen shrub. Every year we have a few cases where somebody is clipping their shrubs at home and they're like, oh, I don't have a place to put them. Oh, there's some horses, I'm just going to put this over the fence. Yes. Never ever, ever put lawn clippings or tree clippings or your fall yard cleanup. You know, just don't put that into any livestock pens whatsoever.


Katy Starr (01:01:50):

And one thing that's unfortunate, and I think sometimes it can be really hard sometimes for owners is sometimes obviously if you know better then you know better. But if you have a neighbor that's nearby and they, like, we have a rental house that's next to our house and they're constantly wanting to like feed the horses and stuff, and it always makes me nervous because I'm like, what are they feeding them? Because like some stuff they can't have. And I've seen other people that have talked about how their, like their neighbor dumped their grass clippings over the side of their fence and they didn't know it. And it ended up being pretty detrimental to that horse. 


Dr. Krishona Martinson (01:02:29):

Yeah, and a lot of times it's not malicious, it's just unaware.


Katy Starr (01:02:31):



Dr. Krishona Martinson (01:02:32):

They don't know. But so like really, I know this, I know your audience here are horse owners, but I wish we could do like a public service announcement, you know, other than slow down on the dang roads. Right? like do not put clippings of any kind. Lawn trees, shrub, ornamental. Just do not put them into any livestock pens. 


Katy Starr (01:02:52):

Yeah. I think that's really, really good. And yes, you're right. We are going, I put this category last because of course it's the worst one. So let's talk about some of these, choke cherry. Let's talk about that.


Dr. Krishona Martinson (01:03:06):

Yeah. So choke cherry is really, so these next ones we're going to talk about the symptom is death. And obviously there's no coming back from that, right? Like these other plants we know in this symptom is photosensitivity or colic or mouth blisters or red brown urine. At least there's a chance we can address it with a veterinarian and hopefully have the horse recover. When you walk out there and find a horse deceased, obviously that is a horrible scenario to be in. It's something that you can't recover from. So the only tree we do want people to remove from their pastures is choke cherry. There is cyanide in many parts of the tree, and we just don't want any accidental ingestion. The same with yew again, that that ornamental evergreen, that is so common. If any of you guys have like an office building that you go into or a university or even like a shopping center, right? Because yews are very hardy, they are everywhere. Highly toxic. And if you are doing landscaping at your property, do not put yews in your landscaping in case a critter gets out. And also, you know, during the holiday season, if you want to decorate your barn with like evergreen wreaths. Which I know is very tempting, just don't do it or do it where a horse can absolutely not even get a sniff, you know, don't put it on their stall doors.


Katy Starr (01:04:29):



Dr. Krishona Martinson (01:04:30):

Because sometimes those wreaths are made out of yew because they are green and they stay green and they're attractive and we just, we just don't want that.


Katy Starr (01:04:37):

Right. And I will ask too, with this category, are these like if they eat like any level, is can it impact them that great of a level?


Dr. Krishona Martinson (01:04:52):

Yeah, so you know, the problem is we don't always know that we're going to talk about, so along with use, we also have hemlocks either poison or water hemlock. And those are really considered some of the most toxic weeds in the entire U.S. And we know that two grams of water hemlock per kilo of body weight or about two pounds per thousand pound is really the lethal dose. And it's, you know, and for other hemlocks it can be less than 1% body weight. So we are talking a very small amount. And with yew, I've never really been given like, or I've never seen kind of an amount, but it doesn't seem to take, it doesn't seem to be much, so that we have a double-edged sword here. The symptom is death and we also don't always know, but it doesn't seem to take much.


Katy Starr (01:05:45):

And so some of these, I think the best thing to do is obviously to be incredibly proactive and just make sure that it's not on your property anywhere. Then you wouldn't have to worry about it. And then if you are in a situation where you find yourself that way, in the worst unfortunate situation, if you have other animals, I guess learn from that, remove them, awful mistake, but then hopefully not have it happen to other ones.


Dr. Krishona Martinson (01:06:09):

Yep. And you know, the hemlocks, there are issues with their roots primarily, but really all parts of the plant. But hemlocks, again, have white flowers and really like to be in a moist wet area. So like I said, wherever, if it's in the shade or a wet area and it has white flowers, it is usually never good.So that's one thing to be aware of.


Katy Starr (01:06:32):

Yeah. Keep your eyes open. And then how about, let's talk about foxglove.


Dr. Krishona Martinson (01:06:39):

So foxglove is probably, some people kind of say that's more of an ornamental or a wildflower. I would say it's more of an issue in the western part of the US. I've never actually seen it growing here in Minnesota. I don't know if you guys have seen it, but it is more of a western plant. And again, you know, foxglove, again, that symptom is death. And also the other ornamentals like rhododendron and oleander, those are also those ornamentals that I think are very commonly known to cause death among horses and even other pets in some case.


Katy Starr (01:07:14):

Right. So we got to watch out for those. Yep. And then box elder seeds.


Dr. Krishona Martinson (01:07:20):

Ah, so box elder seeds is kind of a unique one. And that's one that I actually was fortunate enough to be involved in some research. So in the U.S. and in Europe there's something called seasonal pasture myopathy or atypical pasture myopathy. And through research we have actually found that there's a toxin in box elder seeds. So those little whirly bird helicopters that fall everywhere from female box elder trees. When horses eat those, the symptom is death. Now I don't want to concern people because we really don't even recommend cutting down box elder trees in pastures because they're, I mean, box elder trees are located east to west, north to south. They are a very common tree. And the toxicity is, is relatively uncommon, but it is something to be aware of. We see most of the issues in the late fall when pastures are thin, and horses are eating things because they're hungry.


Dr. Krishona Martinson (01:08:23):

We see issues with adventurous eaters, horses that are described as adventurous eaters or horses that are newly introduced to a pasture where there are a lot of box elder seeds within their grasp. So again, this isn't something that we want people to be aware of, but we don't want them to go out and cut down trees. And interestingly enough, only the female box elder trees produce the seeds. So if you are lucky enough to have a male box elder tree, you won't even have the seeds to worry about. And the tree itself is fine. It is just those little whirly bird helicopters that come down.


Katy Starr (01:09:01):

Yes. Okay.


Dr. Tania Cubitt (01:09:02):

That's so crazy that you say it's only the females. I'm watching this show on TV at the moment, and the suspect of the serial killings is a woman because she's poisoning them and their argument is men don't poison their victims. only women.


Katy Starr (01:09:18):

Then you have the female box elder tree, right? .


Dr. Krishona Martinson (01:09:20):

That's right. .


Katy Starr (01:09:24):

That's so funny. Okay, so we have covered, we have covered so much, but I think a lot of valuable information in this episode. And you talked about it a little bit before, but you know, obviously this is a lot of research and work that you guys have put together at the University of Minnesota for the Midwest. And so a lot of these are common in other parts of the United States as well. But for those that aren't in the Midwest, you know, being able to identify those that are in their area working with their local extension offices. I think you mentioned before Dr. Martinson is a good option. And was there some, there was something else I think you mentioned that they could reach out to as kind of like a resource for them?


Dr. Krishona Martinson (01:10:11):

Sure. So we do have a book and a poster and you can see them on our website. But if, and that's freely available, but if you actually wanted the poster or the book, we do offer that for sale through our website. I know that if you are more in the western part of the U.S., Colorado State has a nice website about a lot of the plants that we talked about, like you said, are found throughout the U.S. but they have a few more that are found in the west. And then Cornell also has a really nice resource for poisonous plants that again, kind of focus more on the east coast. But if you, you know, if you Google poisonous plants and maybe put in your geographic area, your state perhaps, you know, your land grant university or other university might have resources.


Dr. Krishona Martinson (01:10:58):

Sometimes equine nutrition companies will have resources for individuals as well, especially if they've had kind of continuous issues. I mean a lot of people have resources onhoary alyssumin our area just because it's such a common issue. So I think Google is your friend, but the biggest thing is know what should be in your hay and pasture and be very suspicious of what looks out of place. And then, you know, go to those resources like we said before, your local extension office, your Master Gardeners, your agricultural co-ops, you know, other horse owners who are knowledgeable and just try to try to have things properly identified.


Katy Starr (01:11:37):

Excellent. And yes. And Dr. Martinson does have that great poster and that book that especially, I mean, there's so much that we weren't even really able to talk on today that, you know, talking about like control methods for some of these plants or like treatments and things like that. All that information is available in their book. And so we'll be sure to link those in our show notes. So you guys can find those later on after this episode if that's something that you're interested in. Dr. Martinson, how can our listeners stay connected with you after this episode?


Dr. Krishona Martinson (01:12:12):

Yeah, sure. So we, the University of Minnesota Extension Horse program, we do have a monthly newsletter. We do have a Facebook page and we do have a website and all of those are freely available. Obviously, we need your email to send you the e-newsletter, but everything else you can just find by Googling. Yes, those are probably the best ways.


Katy Starr (01:12:32):

And we'll link those for you as well. And I want to mention, I actually talking with Dr. Duren on our, kind of our summary of the Equine Science Society Symposium and some of the things that we learned there. I did mention that, but I love the resource and all the information that you guys share on social media. So I want to make sure that we talk about this again, . You guys did have a situation, unfortunately, where your amazing and wonderful Facebook page got hacked last winter. And so your new one though, we will link it, but your new one is what is do you, do you know what the handle is?


Dr. Krishona Martinson (01:13:10):

Yep. So it's just abbreviated, it's UMN Extension Horse.


Katy Starr (01:13:15):

Right. So again, if you've been missing their posts, which I was for a while, and when Dr. Cubitt was sending me stuff, I was like, why am I not seeing any of this? I realized I had not been seeing it because it wasn't being posted on the other page. So make sure you follow them and unfollow the other one.


Dr. Krishona Martinson (01:13:34):

Yes. That would be, that would be lovely. Yes.


Katy Starr (01:13:37):

So anything else, Dr. Cubitt, Dr. Martinson, that you guys would like to touch on about today's topic?


Dr. Tania Cubitt (01:13:44):

I think Dr. Martinson has done a fantastic job. We knew this would be a long one, but I think it's just great information. I think I would just follow up with most of these weeds, as we've mentioned, are opportunistic and they're going to grow in more prevalently in those pastures that may not be a hundred percent. Or in areas like my fence line where I sprayed. So there are certain areas where weeds are going to pop up more, more often and just go, I don't know whether you can link, I think we've talked about pasture management in one of our other podcasts. Or if we haven't, we really should. And that could be a follow-up to this one as well. To how to stop these things from growing in your fields. But as Dr. Martinson said, really understanding what should be in your hay, knowing what it should look like, then you can see what's out of place. That's how I find four-leaf clovers here. I'm just a wealth of different crazy stories. , you want to find a four-leaf clover stare at normal clover with three leaves, stare at it, stare at it, and then go, then just look for what's not normal. That's how you find a four-leaf clover. There you go. Every time .


Dr. Krishona Martinson (01:14:54):

Oh, that's great advice.


Dr. Krishona Martinson (01:14:57):

And you know, I just, I don't want people to feel like overwhelmed. because we did cover a lot of information and I don't want people to feel panicked. Right. Like generally speaking, poison, you know, toxicity from a poisonous plant is relatively rare in the horse industry. It certainly does happen, but it's rare and it usually happens during times of drought in the late fall or when horses have access to areas that are heavily wooded or shaded or they have unobstructed access to stream banks and ponds and wet areas. So if you have those areas on your property, you need to be more vigilant. Or if you are in the midst of a severe drought, you have to be supplementing hay and keeping an eye on your pasture and those things will help you sleep easier at night and not be overly concerned about poisonous plants.


Katy Starr (01:15:52):

Right. No, that's excellent. Well, thank you Dr. Cubitt for being on today. And Dr. Martinson, thank you for joining us and being our guest expert today.


Dr. Krishona Martinson (01:16:04):

Oh, I had a great time. Thank you very much for having me.


Katy Starr (01:16:08):

Yes. Okay, well thank you and we will catch you all next time. Thanks for listening to The Beyond the Barn podcast by Standlee Forage. We'd love for you to share our podcast with your favorite people and subscribe on Apple, Spotify, or your favorite listening platform. Until next time, keep your cinch tight and don't forget to turn off the water.


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