Feeding the Insulin Dysregulated Horse: The story of checking blood and doing your math!

Dr. Erica Macon of Texas A&M University joins us for an in depth talk on recent research and feeding guidelines to navigate the tricky job of managing insulin dysregulated horses.  And remember, it isn't just the obese horses that you have to worry about!

Transcript

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Kris Hiney: Welcome to Extension Horses Tack Box Talk series, Horse Stories with a Purpose. I'm your host, Dr. Kris Hiney, with Oklahoma State University, and today we're going to be talking about some of the new research with insulin dysregulation in horses, and try to provide some guidance for owners trying to navigate, all of this information. So, with us today from Texas A&M,

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Kris Hiney: Animal Science Department is Dr. Erica Macon, who is a specialist in this area, so delighted to have you, Dr. Macon.

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Erica Macon: Wonderful! I am so happy that you reached out and we get to record this.

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Kris Hiney: Okay, so… I know what we wanted… well, actually, let's even back up. I'm gonna start with,

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Kris Hiney: So, we changed terminology, and sometimes people are like, why did we do that? It's like the whole respiratory disease issue. So, they used to be insulin-resistant horses, nowadays they're insulin-dysregulated horses. Why did we decide to call it something new?

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Erica Macon: Yeah, and I'll… I'll kind of back up a little bit. So, this… this field of research in vet med has

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Erica Macon: you know, kind of exploded in the past decade. And when we first started realizing that we have different endocrine diseases, there was pituitary pars intermedia dysfunction, PPID, or what we used to consider as Cushing's.

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Erica Macon: And we thought that that was the same thing as metabolic syndrome, because we would see them in conjunction so often. And then we realized that equine metabolic syndrome was its own, collective term for all of these things that wasn't just PPID. So…

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Erica Macon: I'll say that we first started out with everything was Cushing's, and then we went from everything is Cushing's to we have Cushing's and metabolic syndrome, and then when we really started to…

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Erica Macon: tease apart what metabolic syndrome is, we realize that not all horses are obese, and when you think about metabolic syndrome, you think of an obese horse or a pony.

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Erica Macon: So, then we teased out what insulin resistance is, and that was kind of thrown around at the same time with EMS. But then we realized that some horses are not always insulin resistant, and by that, I mean…

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Erica Macon: There's tissue insulin resistance, and then there's hyperinsulinemia. So tissue insulin resistance is the inability of the body's tissues to respond to an adequate amount of insulin.

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Erica Macon: And not all horses that have insulin dysregulation have tissue insulin resistance, and I see that quite a lot in even my herd here at A&M, where I have one horse that's this flavor and another horse that's this flavor, but they're both called insulin dysregulated.

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Erica Macon: So now we went from the insulin resistant to insulin dysregulated, because not all horses have both.

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Erica Macon: But in the field, I think we might even see more differentiation in these, in these terms in the future, which I know is just going to be continuously confusing, but now, I think…

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Erica Macon: We see a lot more hyperinsulinemia than we did tissue insulin resistance, because we don't really test

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Erica Macon: For tissue insulin resistance in the field, because it's kind of difficult, now we just look at hyperinsulinemia, and the reason why that's important is because hyperinsulinemia, or high levels of insulin in the blood, are

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Erica Macon: directly linked to the development of laminitis caused by these endocrinopathies. So I think we might see a few more changes in

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Erica Macon: The language moving forward as we get, even better in our diagnostics and really understanding, the differentiations between these endocrine diseases.

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Kris Hiney: So do these horses, that you're talking about that have, maybe tissue-level differences, do they present differently? I'm gonna have this as a two-parter, right? So do they present different… differently to the owner, and then do they present differently to the clinician? Because I think those are different questions.

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Erica Macon: Yeah, yeah, they are. And I'll say… I'll first start with saying that we're seeing so many different phenotypes of these endocrine diseased horses.

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Erica Macon: And most of the time, the ones that are not picked up by the owner may be able to… you may… a clinician may be able to spot them, because they'll see subtle, subtle signs of underlying endocrinopathies that most owners maybe can't identify.

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Erica Macon: So… De… Let's see.

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Erica Macon: Repeat your… repeat your question again.

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Kris Hiney: Just, like, I think there's, like, what does an owner see? Okay. Or… or is there something that, you know, a veterinarian is picking up on? Because you said they may pick up on something a little bit differently, but oftentimes it's the owner, right, that's gonna request

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Kris Hiney: You know, further testing or have concerns, and so what might then, like, lead them to that direction?

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Erica Macon: Yeah, most of the time, the owners will pick it up.

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Erica Macon: when the horse becomes laminitic, and they're unsound. So then you'll have the vet come out, and the vet will see the subtle signs. Maybe that horse has a crusty neck. Maybe it has a little bit of extra padding behind its shoulder. And sometimes I…

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Erica Macon: I've gotten this a few times. Owners will notice that the pockets above the eyes are filled in metabolic courses. I've only seen that a couple of times, and I don't know why that is. But I've had a few owners point that out. They're like, they used to have, like, a pocket there, and now it's full, and it's kind of squishy, like, fat-feeling.

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Erica Macon: And…

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Erica Macon: owners otherwise might, if they have PPID, they might see the shagginess in the coat, and those… that's the most, you know, classic sign for that. But they may not really pick up on the regional fat, whereas I think some of the veterinarians are really going to see that, because we know that at Cresty Neck.

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Erica Macon: Or just that deposit of fat above the nuchal ligament along the neck, is probably one of the best indicators of insulin dysregulation, but fat elsewhere doesn't always say that.

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Erica Macon: And I've seen many horses that they… you can see ribs. If you think about body condition scoring, which is very difficult in these… in these different endocrine diseases, because you can have a horse present

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Erica Macon: where you can… you can actively see the ribs, so there are 4 or below, but they have this regional fat, so how do you score that? And that's probably one of the most difficult things from an owner perspective, because they see the ribs and they say, I need to feed my horse more.

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Erica Macon: Because you can see those ribs. But really, they have an underlying insulin dysregulation, but they're a lean phenotype. We really haven't been able to…

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Erica Macon: characterize a lean phenotype versus an obese phenotype, we just know they're there. And then, you know, if you have a horse that has PPID, and you can see their ribs.

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Erica Macon: But they also have insulin dysregulation. Those are the hardest ones to… to manage, and oftentimes the hardest to spot, to an owner, because they don't know the insulin dysregulation is there. They know the PPID is there, but they…

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Erica Macon: They associate the rib… you can see the visually for the ribs, and they're like, we need to feed this horse a little bit more, because it's not getting enough calories, but you don't know that you might be kind of feeding into,

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Erica Macon: the insulin dysregulation and may trigger a laminitic episode. So, I always tell people that we should, you know, do a screen for endocrine disease, even if you think

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Erica Macon: for whatever reason, your horse is completely healthy. We don't know exactly when, you know, that horse flips over into the disease state. We do know there's a spectrum, where you have ones that are just now having signs of the disease, versus very late disease, where you see so many complications.

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Erica Macon: So, even though we don't really have… it's not even… it's not a guidance, an AAP, or anything like that, I tell people that have a easy-keeping horse.

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Erica Macon: Or they always, you know, they stay fluffy on air. You know, maybe you should screen those horses once a year and just check and see what their levels are, so you can maybe get ahead of it if it does develop.

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Kris Hiney: And I wonder, and sometimes I wonder, is it because I teach more about this, and this is part of my messaging, because I do get more questions about it, but I do think people are doing a little bit more routine screening.

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Erica Macon: Oh, good.

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Kris Hiney: for hyperinsulinemia, at least that's kind of some of the people that are headed my way. And we're going to get to feeding them in a second, but

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Kris Hiney: So, I think especially people that have had, like, the high-risk breeds, or have had that kind of,

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Kris Hiney: record, like, I've even had owners that are like, well, he's not hyper and insulinemic, and I was like, well, then don't panic, just keep him in a good… like, don't do anything yet! Like, you're still okay. But I do think people are getting a little bit more aware of this.

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Kris Hiney: So I have maybe a couple questions, and I want to get them on the… well, I guess the order doesn't matter.

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Kris Hiney: because one thing that I've been asked by, maybe more of my, traditional audience or educators is that, are there… are there really more of these horses now, right? Are we seeing a progression into the population of more of these types of horses.

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Kris Hiney: Or conversely, are we simply more aware and better at picking them up?

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Erica Macon: Yeah, I think we're more aware now, and our diagnostics have improved so much, and…

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Erica Macon: Now, in terms of prevalence, if you think about prevalence of these endocrinopathies, especially in PPID, we have a bit more of understanding that about 30-40% of senior horses, probably… or probably have Cushing's.

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Erica Macon: But in terms of prevalence for insulin dysregulation and hyperlinsanemia, we still don't actually know those numbers here in the United States.

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Erica Macon: one… papers from Europe and Australia, they have a very wide range, because you have to think about what kind of breeds they have in Europe, and what their management style is. It's very different from how

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Erica Macon: our management style in the U.S. is. They have really high NSC grass, NSC non-structural carbs.

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Kris Hiney: Oh, I've seen their numbers. I'm like, what kind of magic grass is this?

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Erica Macon: Yeah, it's… it's crazy! So, when I did, some, pasture work here in the U.S, but we had a British collaborator, Dr. Pat Harris, she was like, I just am amazed at the NSC levels in your grass, and I'm like.

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Erica Macon: Yeah, if they're not that high, she's like, not in Europe. So those horses are managed differently, and the different papers that have come out, the range on those is 16 to 60% of the population might have insulin stripulation, which is a huge

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Erica Macon: Huge range. And, you know, some of the papers that had those values were done in, you know, Welsh ponies, which are one of the breeds that you look at them wrong and they go, you know, blow up. So, in the U.S, I'm actually…

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Erica Macon: in the next month or two, gonna release a national survey to try to quantify endocrine disease in the U.S. So hopefully I can get a bunch of people to take that survey, and we can get a better understanding of, one,

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Erica Macon: how we could try to quantify the actual prevalence, and two, how they're managed, and how the owners found out about it. So hopefully that will be helpful.

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Kris Hiney: Yeah, no, that should be super helpful. Okay, now I want to actually get to the whole point of what

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Kris Hiney: I asked you to be on today. But I think the background information is super important for owners to kind of hear this. But there's been a lot of work

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Kris Hiney: oh, I think it's in the last 10 years, but a lot of it's kind of really pretty current.

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Kris Hiney: about looking… so, like you said, so NSC has always been our, like, our trigger words for horses with, hyperinsulinemia, insulin dysregulation, and to avoid that. But… but there's two things that have kind of come out recently that I… that we can address one at a time.

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Kris Hiney: One is that it's maybe not just NSC, so maybe we should just… let's talk about that one first before I give you a two-part question. So, what else in the diet, other than this, just non-structural carbohydrates?

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Kris Hiney: Do we might need to think about in these horses?

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Erica Macon: Yeah, and there's… there… there's been a lot of work, at least in the past 2 or 3 years, that have come out, and we're really focusing on how can we control

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Erica Macon: post-meal insulin levels, and, you know, what… what dietary nutrients are responsible, for making those responses, go higher. So, there's been a lot of work by a couple of individuals that is looking at amino acids and protein,

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Erica Macon: And while I think some of… some of the papers that did come out, they used very pure and bioavailable sources of amino acids, and they fed them in an amount which I don't believe a horse would ever see in a commercial practical standpoint.

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Erica Macon: Now, is there a lot of research in humans that shows that some amino acids are insulinogenic, or make… or that…

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Erica Macon: Meaning that they would, increase insulin responses just because of the particular pathway, which we won't go into the details of that pathway, because it's really complicated. But…

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Erica Macon: I do think that if you were to feed bioavailable sources of protein in a high amount, you would see an insulin response, but impractical, I don't believe you'd ever see that in the industry. There's been a little work about fat, and we think

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Erica Macon: I…

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Erica Macon: most of the work has shown that fat could be a source for energy to put weight on a horse that is potentially insulin dysregulated if they did need weight, because it's a safer way, to add that weight to them without, stimulating insulin secretion.

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Erica Macon: And of course, there's… there's NSC. And I'm gonna go back to the protein and NSC, because one of my… one of my papers, we were trying to tease out, is it…

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Erica Macon: is it protein, or is it NSC? And we had that question because we were looking at, we looked at protein out in grass, in… in Kentucky, and…

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Erica Macon: we found, as protein and NSC increased, and we didn't differentiate because they were out on grass,

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Erica Macon: we had bigger responses, so we were worried that protein could be a driver of the insulin response. So then we did a pelleted study where we used a ration balancer, which, of course, those are high protein.

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Erica Macon: And we saw they had a huge response to the ration balancer. It was actually very similar to cracked corn, which is terrifying. So we got really scared when we saw those results, because we're like, this is what we're telling the industry to do, to defeat a ration balancer.

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Erica Macon: So then we started teasing it out. So, we had,

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Erica Macon: I believe we had 3 different levels of crude protein, and we only had 2 NSC levels. One was low, one was high. And despite the…

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Erica Macon: different protein levels, we only saw the difference because of that NSC, not the protein. So we kind of shifted and said, alright, if we have these in a combined fashion, NSC is going to be more of a driver than protein is.

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Erica Macon: So, I think, I think I answered that question, correct?

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Kris Hiney: Yeah, I think so, but I thought even, they did some work in Europe, too, that was relative to protein, because traditionally we've said, like, no, no, these things are perfectly fine, but they've seen some, like, well, maybe there's some hints that

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Kris Hiney: And this might get to the, kind of, the two-parter question here, of that some horses actually mounted a much higher response to some of those high-protein males than other horses did.

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Erica Macon: Yeah, yeah, and… and that's absolutely possible.

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Erica Macon: That goes into the more individual response, but… I think…

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Erica Macon: I'm trying to remember… so there's been a group here in the U.S. that's done a lot of protein stuff, and there's a few over in Europe that have done some protein stuff, but if you… most of the feedstuffs, unless you're feeding… okay, first, let's back it up. The one… the papers that are here in the U.S. fed pure sources of amino acids.

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Erica Macon: But in those sources, the NSC in them exceeded the threshold that I found. So we can't really differentiate whether it's the amino acids or it's because we just passed that threshold.

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Erica Macon: And I think in any of the other feeding studies, the NSC threshold has been passed, so it doesn't matter. Once you pass it, they're going to respond. But I still think we need a little bit of work in that area, because we can't…

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Erica Macon: we can't really definitively say, is it just individual amino acids? Is it a particular gram amount of protein? You know, because we do know that

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Erica Macon: mTOR, which is the pathway I referred to earlier, that can be activated by insulin as well, which is why some amino acids are insulinogenic. I think we have some questions to answer in that area, but

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Erica Macon: I still think that NSC is more of the driver, just because of its… Oh, let's see

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Erica Macon: It's quicker in terms of getting a bigger response than amino acids would be, if that makes sense.

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Kris Hiney: So, so along with all these, papers that… that have come out recently, the other thing that, you know, when I read through them, and the author's note as well, is that

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Kris Hiney: you know, and to frame this for the other, like, so when we do research, there's means, right? You do statistics, and you say, this population is significantly different from this population. So it's all means-driven, right? So you're two populations. But within those studies, there were… there were individuals that responded

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Kris Hiney: much more dramatically to some of the, treatments, or the feedstuffs that they were giving them. So what does that inform you as a researcher and as an owner, right, as to how does one navigate the way forward?

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Erica Macon: Yeah, and I've stared at thousands of insulin response tests.

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Erica Macon: And… and most of them were in the same group of horses, and every single time, I could have given them the same exact thing, same amount, same dose.

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Erica Macon: everything in similar conditions, and they respond differently. And by differently, I mean that the concentrations were either much, much higher, maybe they were a little bit lower, but I think one… the first reason is because insulin is affected by so many things environmentally.

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Erica Macon: You know, the horse is really good at staying euglycemic, or having normal, stable blood glucose.

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Erica Macon: It's rare that we'll see, blood glucose get out of whack, even if we have really high insulin levels. That's still a perplexing topic for most people that are in this field, and someday we want to figure out why that is.

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Erica Macon: But… It… with…

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Erica Macon: if you go back and we look at all of the different feedstuffs that I've tested, and most of it wasn't… some of that even hasn't been published because it was more of commercial testing and stuff like that.

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Erica Macon: you… the individuality really goes back to severity of disease.

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Erica Macon: If we see a horse that has…

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Erica Macon: Okay. Actually, I'll give you an example. I have two horses in my herd. One is Tango Mango, and the other one's name is Monty. Monty is a Mustang, and most…

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Erica Macon: Spanish… Breeds, if you can… Think of some of them other than just, the.

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Kris Hiney: Andalusians. Yeah, yeah. Yeah.

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Erica Macon: Those guys have a… predisposition to developing metabolic syndrome. And that's what Monty is.

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Erica Macon: Tango Mango is a little quarter horse. He is… he has PPID, he's very fluffy right now, you can really tell. But he responds positive to an OST test, and when I say by positive, he will have

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Erica Macon: positive insulin in terms of the over-the-threshold level for the OST. But then, if I give him a meal.

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Erica Macon: he won't have postprandial hyperinsulinemia, even if it exceeds the threshold. But… and he doesn't have tissue insulin resistance, he just has a positive test on the OST.

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Erica Macon: But then if you look at Monty.

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Erica Macon: he has a very high OST value that comes, in insulin concentrations. He's also tissue insulin resistant. I say Monty is further along in disease than perhaps Tango is.

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Erica Macon: And that kind of goes back to severity. Now, do I think that every horse that has tissue insulin resistance and hyperinsulinemia is going to be higher on severity? No, because it really is a spectrum for these guys.

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Erica Macon: But…

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Erica Macon: When it comes down to the individuality, if you have a horse that responds really high to their feedstuffs, that's a horse that I'd be really concerned about managing their diet. For a horse that's positive for an OST, but then you feed them something and nothing happens.

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Erica Macon: okay, maybe that's a little bit different. And some things that I've been suggesting to owners right now is to test

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Erica Macon: their horse's responses to their dietary feedstuffs. Because you can do an OST, like I did in Tango Mango and Monty, and I get a positive result in both of them, but then when I give Tango a ration balancer that's still over the limit of NSC, he doesn't respond.

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Erica Macon: But… but Monty does. So, I think it's…

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Erica Macon: it's, again, it's a spectrum, but I recommend people test whatever they're feeding, and make sure they don't have this recurring

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Erica Macon: You know, postprandial hyperinsulinemia, because

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Erica Macon: The biggest thing about that is we don't know how many times a horse has to have

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Erica Macon: a very hyperinsulinanemic phase after eating to trigger laminitic events. And we do know that there's quite a bit of subclinical laminitis, and by subclinical laminitis, I mean

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Erica Macon: laminitis that's not picked up.

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Erica Macon: By the owner, maybe even the clinician, because they're not… they don't seem unsound. But the lamina are changing every single time they have this hyperinsulinsemic event.

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Erica Macon: It's hard to really characterize that, but we believe that's what's happening, especially if you look at something like radiographs over time, and maybe you have never seen them to be on sound, but they're, you know, they're making these changes.

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Erica Macon: And I think the diet impacts that so much.

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Erica Macon: But it's really hard to try to catch it, because you don't see them being unsound. And the only way we can think to keep that from happening is by controlling their responses to their feedstuffs and limiting the amount of… amount of time that they do have postprandial hyperinsulinemia, or post-meal hyperinsulinemi.

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Kris Hiney: And that was definitely gonna be my question, like, how often can they get that way, or how high?

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Kris Hiney: So my next… so my practical question off of this, then.

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Kris Hiney: So, we kind of mentioned that owners are becoming more aware, right? And they're screening. Yeah. And they're picking up on, yes, my horse has hyperinsulinemia, and there's… there's a threshold, and we don't need to go values here, because that's not the point of this, it's more educational. But if your horse is… is in the zone of what we call hyperinsulinemic.

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Kris Hiney: So, would you recommend that… obviously, diet… address the diet, right? So, we want to, you know, follow the guidelines, smaller meals, the concentrates, trying to limit the NSC, but

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Kris Hiney: Which owners, is it all owners, or is there again in the spectrum, that should think about testing the insulin response to their diet, or their meal feeding?

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Erica Macon: Yeah, and…

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Erica Macon: I… I would hate to say, let's keep it for the most severe guys, because I do think that as that animal ages, the disease is also going to get worse.

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Erica Macon: Especially if they're not managing it correctly. And by managing correctly, I mean just…

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Erica Macon: keeping tabs of the NSC that's in their feedstuff, or the calories that are in their feed, so they don't continuously add more adipose tissue, because more adipose tissue gives these things called adipokines. You lower the good one, and you raise the bad one, and that's a whole new thing, but I think…

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Erica Macon: to be safe, and to make sure their horses don't develop any laminitic, signs or laminitic changes over time. If you have a horse that screens positive for an oral sugar test, and

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Erica Macon: you go and you try… and you try their feedstuffs, and you don't see a massive response. Normally,

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Erica Macon: if I see anything over…

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Erica Macon: I mean, it really depends on how much NSC is in the diet, but if I don't see a doubling in response, I feel okay. And even if that does happen, I would still say keep your animal on a low NSC, feed stuff like a ration balancer.

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Erica Macon: Other than the fact if that horse is very lean, and they have regional fat, but they need to gain some weight, we go down a different

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Erica Macon: a different road to how we would manage that horse. But I still think it's… we should… we should err on the side of safety, and if they screen positive.

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Erica Macon: You should definitely try to keep that animal managed

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Erica Macon: Fairly, specifically, just so you don't get to that point where you are so high on the severity of disease, that it's hard to manage them, if that makes sense.

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Kris Hiney: And the management, because I know when I speak to owners, this is often the hardest

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Kris Hiney: honestly, the hardest part, and I wish there was simpler things, but we'll go over it, right? So we always are like, okay, we want to keep them in a leaner, more moderate body condition. You want to make sure that you're feeding low NSC hay, but there's the whole, like, well, where do I find that, and what about all the other horses? And then we add in, well, don't let him smell the grass, and like, now where do I keep it? Because now he's unhappy, like.

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Kris Hiney: Do you have any practical guidelines or suggestions? Because we're always real big here on mental health of the horse on this podcast, so, like, where is this balance, and what is an owner to do when you don't really have complete control over environments often?

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Erica Macon: Yeah, and that… that seems to be the biggest thing for every owner that I talk to. It's always, you know, the welfare of the horse. It feels compromised when you try to manage a horse with really severe insulin dysregulation. I have…

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Erica Macon: I've done a consult for a farm that has Paso Finos, and that's also a breed that's very known for metabolic disease. And I'll say that

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Erica Macon: one was very severely insulin dysregulated, to the point where she had, you know, she had multiple, episodes of laminitis, and even rotation.

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Erica Macon: So, for her, they kept her up in a stall the whole time, just because they didn't have a dry lot. They had very luscious grass, and this is here in Texas, which when I say luscious, is, you know, Texas grass.

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Erica Macon: But this… this Paso Fino was still able to respond to it. And I had recommended for them, once she… once she was, you know, the vet said she was sound, all that stuff, that maybe they should build her a little track.

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Erica Macon: And then have, you know, slow feeder hay nets or something in her little track, which, that is a lot of infrastructure for most people to try to implement. And I myself have been thinking, okay, how can we actually improve the welfare of these horses?

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Erica Macon: So I just got a… I just got a Morris Animal Grant, to look at different types of interventions for feeding forages, and if we could…

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Erica Macon: lower the postprandial response, but still maintain really good welfare and soundness of mind, where they're not getting super frustrated. I'm hopeful that that project will start some point.

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Erica Macon: This summer, that maybe we can find some new ways to make sure the welfare is, in a good place, because owners really don't like to put

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Erica Macon: muzzles on their horses because they get so frustrated. So can we improve how the muzzle is made, or, you know, make some modifications?

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Erica Macon: It's always… it's always the biggest question, because they don't want to keep a muzzle on 24-7.

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Erica Macon: And we're running out of options for how do we give them a quality of life, but still maintaining them so they don't have that postprandial hyperlins anemia. It's my biggest problem. Have you had any luck with any suggestions?

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Kris Hiney: I mean, that's a lot, you know, you go back to slow feeders, double net those slow feeders, you know, some would argue, like, well, does that create frustration? But there's a little bit of, well, I'm at… at least we're still getting grazing patterns, still making social contact, so… and I get it, where you're like, well, can you still have them around the other horses? And, like, it is… it is not an easy conversation, and because

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Kris Hiney: I, like yourself, am always emphasizing what is… what are you doing to the mind of the horse, right? So we're into the big five domains, the mental domain, right? Because health doesn't matter if your mind is shot, right? Yeah. So, I'm really excited to see what you come up with, because that is, like, super impactful.

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Kris Hiney: Yeah, because my… my solutions are very much, like, if they're going to go out on pasture, put the grazing muzzle, can we have dry lots with friends, can we double bag that hay? Like, to try to do these, just slow things down, use those puzzle feeders, like.

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Erica Macon: Hmm.

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Kris Hiney: Give them something to do, to keep them occupied.

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Erica Macon: Yeah, and I have the… that project has two different styles of interventions. One's for pelleted feeds, and the other is for forage. And we're… we're testing multiple different ways, you know, using soap hay with a muzzle, and

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Erica Macon: you know, different… different types of bags, you know, compare it just to feeding on the ground, just so it's, like, a positive control from some of the other ones. And we're doing 12-hour and 24-hour sampling to see what the insulin looks like through the day, because that's what we… what we need to see. You know.

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Erica Macon: I can go and test a particular feed, and I look for about, you know, say, 2 or 3 hours after that horse has ate that meal, and look to see what insulin does.

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Erica Macon: We haven't really seen a lot of, long-term sampling and looking at how does meal in the morning and meal at night impact the horse response? And then, you know, what about putting all of that stuff together and using the different interventions so we can, over a 24-hour period.

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Erica Macon: Try to lower those insulin levels down after they're eating things.

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Erica Macon: And hopefully that would decrease laminitic events, I would hope, or laminitic changes. But…

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Erica Macon: Yeah, I don't think we have the greatest solutions yet to welfare for these horses. I think we need to put a little bit more effort into that, but there… a couple companies over in Europe have developed, like, the slow-release feeders.

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Erica Macon: I think those are great, but they're really expensive. I've seen some, like, at-home

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Erica Macon: things that people have made, and they're pretty… pretty smart. But other than that, I mean, it's… it's still the same practical things we have. Muzzles, different hay bags, that kind of stuff. I wish we had something better for them.

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Kris Hiney: So I'm curious, are you guys doing some behavioral or mental metrics in your study as well?

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Erica Macon: Yeah, yeah, we are. And I may actually reach out to you and see if you… if my… if you have any other comments or, things, if you want to look at something in the project, because it has two different experiments, but we're going to look

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Erica Macon: at welfare on both experiments. Just from, obviously, since it's such a hot topic, maybe we can find some new stuff, or, see something we haven't yet.

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Kris Hiney: Yeah, no, reach out, this is fun. But, I mean, and again, I don't know, like, where I said, I think people are just so much more aware, they're trying to do the right thing, and we're trying to come up with

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Kris Hiney: with good answers for them, and that's why the, you know, the work that you're doing, I think, is super, super critical and super applied, and, like, we love some applied research here and there, so…

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Erica Macon: Yeah, and I think whenever, even when I teach equine nutrition to, you know, grad students or undergrad students, I say, go back to what the horse was meant to do. And if we can try to mimic what they're naturally meant to do, and we're also making sure

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Erica Macon: we're feeding the correct parts of their GI, and I always say anatomy dictates function. And if we're really, really supporting the hindgut and eating, you know, some low NSC forage, and then you combine that with different interventions, maybe that's the best thing we can do, trying to get them closer to what they're supposed to be doing.

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Erica Macon: And… And again, I think the reason why

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Erica Macon: I always go back to this, is because starch levels in grass here in the United States

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Erica Macon: are so low, 1-2% most of the time, and they get mostly water-soluble carbs out of that. And that tells me that starch was never meant to be very high pre-cecaly, or before the hindgut. So if we are feeding them, we have to keep

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Erica Macon: we have to remember where the anatomy is and how it functions. So if we lower that in response in their diets, you would hope to see some improvement, too.

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Erica Macon: That's… I always say that to my students.

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Kris Hiney: But I… it's a good attempt. And that's, it's kind of fun, because that's how I've started to evolve my teaching, too, is always to be very… I'm, like, how does everything hit that mental domain? So that's our central tenet, like, think back about that, think about the ethology, and…

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Kris Hiney: Look, I made this behavior anyhow.

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Kris Hiney: No, but I think it's… it's a critical piece. Well, I have really enjoyed this conversation, and I'm super excited to share it with people. I think it helps them understand that, yes, we don't have all the answers, but we're trying to keep coming up with new guidelines, and why we keep changing our story and coming up with different words, which frustrates everybody, but that we have a community of people.

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Erica Macon: that are… that are working on this, and so I think that gives us hope as horse owners.

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Erica Macon: Yeah, and, you know, different… there's not very many of us that work in this particular field, if you put into perspective, like, someone that does diabetes research. There are many people that do diabetes research. And I think every single one of us has

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Erica Macon: a theory or an idea that we're chasing and saying, okay, if we do this, we can make things better. And I think that's what makes research so great, is because we all have these creative minds that are trying to tackle a problem from multiple avenues.

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Erica Macon: Mine is just, I want to figure out where the physiology goes wrong, and can we correct it? Or if we can take that animal and take them back to what they're supposed to be doing, can we improve it? More like a holistic aspect, I mean. And then…

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Erica Macon: The Australians, researchers, and I don't know if you've heard of any of this recently, but SGLT2 inhibitors, have you heard those?

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Kris Hiney: Well, because of, you know, all the other things.

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Erica Macon: Yeah, yeah. So those are… those are really promising, for acute laminitis. Before, we didn't really have anything we could give them for acute laminitis, and now we… we're using these SGLT2s, and they're incredibly promising.

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Erica Macon: And that's what one of the Paso Finos that I was helping on a nutrition case

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Erica Macon: was put on, and she had 180. In a few months, she was able to be ridden again, and was doing much, much better. The only negatives about that are it does…

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Erica Macon: affect liver health, so you really have to monitor when you put a horse on one of these SGLT2s. But they can really try to get you through an acute episode. I've only known an instance of one horse that's been put on an SGLT2, and

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Erica Macon: they did not respond, but I think there was some underlying genetic differences in that particular horse.

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Kris Hiney: So, and I'm just gonna fill it. So, you were talking about sodium glucose transporter agonist, right? So, just to give people the lingo.

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Kris Hiney: there's a bunch of different, transporters, but this is a specific one, so it would change glucose uptake, just to fill in some of the science-y gaps for people. And if you've got time, I thought we were gonna wrap this up, but now I'm gonna go back to GLP-1s.

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Erica Macon: Sure, yeah.

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Kris Hiney: Okay, where's that in the whole…

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Erica Macon: Yes. Well, you know, GLP-1s are hot in humans right now.

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Kris Hiney: Hot and humans.

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Erica Macon: Yeah, they're, they're, they're being used rather frequently. So, and this was a lot of work that Melody DeLotte, she's one of the Australian researchers, probably one of the best ones, honestly, and she's the one that did

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Erica Macon: the beginnings of GLP work, in horses and ponies. I believe most of it's in ponies. But the incretin response in horses… oh, hold on, I'll…

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Erica Macon: define that. So, incretin hormones are the GLP-1, and there's also another one called GIP. These hormones are actually made within the intestine, so if you have glucose in the intestine.

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Erica Macon: these particular cells, they'll sense it and be like, hey, we need to release more insulin, so they'll release that GLP-1 or GIP that goes back to the pancreas and say, hey, we need to respond more, because there's lots of glucose.

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Erica Macon: In humans, that, incretin response, which is what we call the GLP and GIP, is about 75%, or is responsible 75% of the insulin response.

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Erica Macon: In humans, which is why they're so effective, because that's 75% of that response. In horses, we estimate that to be about 20%. So they're not as effective as effective as humans for an incretin response. Why that is, we don't understand that.

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Erica Macon: Which is why we kind of moved away from the GLPs and horses and ponies, because it wasn't as effective. Now, the SGLT2's different mechanism is really effective. And again, why that is, I don't really understand.

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Erica Macon: But my theory is that…

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Erica Macon: horses were meant to see more water-soluble carbs coming from fresh grass, and the SGLT2 and that particular transporter, I believe, would be better at

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Erica Macon: getting rid of that glucose, then the incretin response going back, and saying, hey, we need more insulin. Because if a horse is hyperinsulinemic.

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Erica Macon: they're most likely going to have resting hyperinsulinemia, although not all do. And I think we're just… there's two different mechanisms in the horse, and why those work. But again, we don't have, like, definitive why this works, why this doesn't work. It's just what we've seen so far.

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Kris Hiney: It's just… it's not going to be on the table. That drug is not going to be on the table for… for horses. And I know I saw something, and I'm just going off on a tangent now, so you can be like, just stop. But… because it came up, and so I teach a class in the

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Kris Hiney: In the fall, I teach a companion animal class, now that I can talk about ethics, and so that came up as, like, people putting their pets on… on this, potentially, but it's not there. But my students, and I thought they were very insightful, so I really appreciated them in this moment, they're like, well, we know so many people that they feel so terrible.

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Kris Hiney: on these drugs, can we really do that ethically, to…

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Kris Hiney: pets, and I was like, oh, I think I love you guys right now. So it's really interesting, and it adds just another, another piece of the puzzle.

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Erica Macon: Yeah, that just makes it more complex. Yeah.

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Erica Macon: I know, and I… I know people that are… that are on GLPs that… that they feel like crap all… all the time, and they're… they say that they're never hungry. They have to force themselves to eat. Yeah, so what does that do to the welfare and the mindset of the animal?

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Erica Macon: Right. That, especially a horse, who's supposed to be a constant grazer. Yeah.

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Erica Macon: Yeah, that… that's different. But GL… I know GLPs do that. I don't know if SGLT2s have the same neuroendocrine effect, because we do know that there are receptors for GLP in the brain, but SGLT2s, I don't know if that's the same

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Erica Macon: that would produce the same neuroendocrine effect, I guess is what I'm trying to say.

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Kris Hiney: Interesting. Well, I mean, that would be another little side project for those guys in Australia. Look at the behavior. And I know the Australians are big in behavior, right?

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Erica Macon: Yep.

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Erica Macon: Yeah.

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Kris Hiney: It's something that they're known for, well, at least the community that I'm aware of, so… Yeah. Okay, I promise I'll stop now before I bring something else up, but, because I am always really intrigued by this, and try to stay pretty current, in some of this data, so…

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Kris Hiney: All right, well, I really appreciate your time in allowing me to rabbit trail lots of things here.

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Kris Hiney: So, definitely appreciate it, and certainly, Dr. Macon, if there's any articles where you think, like, because I know sometimes our listeners want some deeper dives, if there's some helpful things, send them my way, we can link them to it, provide some more resources for horse owners.

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Erica Macon: Yeah, absolutely. Thanks for inviting me. I love… I was… I was supposed… I'm working on a grant today, and I was… I… yesterday, I was looking at my calendar today, and I'm like, oh, I get to talk about this stuff, yay! Which is much more… much more fun than writing the grant.

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Kris Hiney: It's always more fun than writing your grants. Well, again, really, really appreciate your time with me today, and this has been another episode of our Tack Box Talk, Horse Stories with a Purpose.