Horse Nutrition Q&A: Insulin Sensitivity, Muscle Building and Misleading Feed Labels
Podcast #64
Join Dr Nerida and Orla as they discuss how powerful exercise can be for insulin sensitivity, metabolic health and weight management. Plus they talk feeding for muscle development, and how whey protein, soybean and leucine play a role.
They also dive into digestive enzymes, why they are being added to more feeds, and how enzymes may help some horses digest starch more efficiently when grain-based feeds are used. This leads into a bigger discussion about diet analysis, nutrient deficiencies, toxicities, misleading “grain-free” labels, and why horse owners need a way to check whether a diet is genuinely safe and balanced.
The episode finishes with musings on raw grain, stomach pH, hindgut pH, gastroscopy, omeprazole, acid rebound, and has a few classic Orla and Nerida side tracks along the way.
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🩺 And if you’d like to get in touch with Orla, Orla.lyons@randlab.com.au
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Hello, and welcome back to the Happy Horse Nutrition Podcast. You are with Dr. Nerida, and I have Orla with me again today. Welcome back, Orla.
Hi again! And Orla is sitting on my office floor, and it is Friday afternoon. I think I’ve been awake since about 3am this morning. Orla has been on the road all week, and anything could happen, so if you’re wanting a serious podcast to listen to, maybe don’t listen to this one. But we will try to get through some good nutrition questions and hopefully speak some kind of sense for the next half hour or so.
We’ll try. You still learn something though.
Exactly, in some roundabout way.
The Sydney Pony and Insulin Sensitivity
ORLA: I’ve been binging your episodes knowing that we were going to do this, trying to get some inspiration. I had a giggle because of the episode with Dr. Brian Nielsen, talking about movement, and how Joanna takes her horse for a walk like a dog. It reminded me of a guy in Sydney. He was quite old at the time, back in 2018. He had a pony called Lusha, and he would cycle it around Sydney every single day, kilometres. And this pony was fed Easy Feed 3.
And I was like, are you sure? He goes, Orla, it’s the fittest thing you’ll ever come across. You can Google them. And I looked it up, and there were photos of him cycling around Sydney with his pony trotting in front.
NERIDA: Easy Feed 3 is a racing feed, right?
ORLA: Yes.
NERIDA: And normally, if you fed that to a pony, you would blow their feet off. They would be so insulin dysregulated that if you gave them that for even a couple of days, I imagine you would do pretty serious damage.
But that’s a really good demonstration of how much exercise can change insulin sensitivity. We talk about weight loss diets and managing metabolic horses, and the biggest part of managing a metabolic horse is having them fit. Move.
I say that with full knowledge of our most metabolic horse having sat now for a year and not being ridden, because Tamaya moved off onto Alay. Popcorn is heinously metabolic. She’s got a cresty neck and gets overweight so easily. Doug weighed her the other day, exactly 12 months after we weighed her last year. This time last year she was Northwest Horse Expo fit. And this year she is very unfit, to the point where Alay unfortunately went lame, so Tamaya’s not riding her, and people have said, what about Popcorn? I’m like, Popcorn’s so unfit she wouldn’t cope, even if we just took her to a dressage day, I think she’d bus something.
And Doug, when he did her teeth the other day, I’m there going, are you sure your scales are accurate? She put on about 30 kilos, which is a lot for a horse that’s meant to weigh 450 kilos. She’s closer to 500 kilos, my whole Popcorn. This is not good.
It’s so important to have them fit. And when she was fit with Tamaya, I had so much more room for error in her diet, because she had much better insulin sensitivity. Whereas this year, there’s a post on our Instagram and Facebook pages if anyone wants to go and find it, but I put a post up going, Popcorn’s got a pulse. She’s right on the edge of being laminitic, and all I had done was open them up onto a new paddock with strip grazing. I looked at the grass, it was all dead because it was so dry, but it must have dried off when it was quite high in sugar content. And that was enough to tip her over, because she’s not fit, and she’s lost all that insulin sensitivity that she gets when she’s in work.
ORLA: That’s interesting. So the Sydney pony was a really good example, because he was fit as anything, being fed a racehorse feed. And then even at the mini shows, I can hold those minis in carts, in hand, and these things were getting fed Stamina, which is a racing feed but concentrated. And I’m like, can we feed them anything? And they would, again, there was a lot of lounging, but they were fit.
NERIDA: And where that’ll start falling apart is if they stop exercising those horses and keep feeding them that way.
We were talking about this in the last episode we did together, which was about ten minutes ago, but by the time you guys hear this it’ll be weeks ago. We were saying that if you feed horses that have got a metabolic predisposition because of their breeding, you’re much better off feeding them as if they are already metabolic. Even for that pony, he’s doing a lot of work, but I’d be still trying to feed him on a grain-free diet.
The research done at University of Melbourne, Simon Bailey, maybe Nick Bamford, and Sam Potter may have been in there somewhere, found that if you got horses fat on a starch-based diet, they had less insulin sensitivity than if you got them fat on a fibre and oil-based diet. It seemed to make them worse. But he’s not getting this pony fat, he’s getting him super fit. So there’s a difference there.
ORLA: It also made me think that because he’s cycling on the road, this pony is just trotting on hard concussion ground. It’s going to have the healthiest bones, healthiest joints.
NERIDA: Very cool. I hope he’s still alive.
Whey Protein: How Much and How to Use It
ORLA: I went down a rabbit hole on your most recent protein episode. Whey protein. How much are we talking when we’re feeding whey protein to a 500 kilo horse?
NERIDA: It’s not much. Somewhere between 100 and 150 grams. A bodybuilder’s dose is like 30 to 40 grams in one hit.
They can’t feed whey protein in Europe to animals, because you’re not allowed to use animal protein in animal feed. But it’s very much legal here, and I think in the States too.
The thing with whey protein is it’s really, really high in leucine, and leucine is that one amino acid that literally flicks a switch and turns muscle building on. So you’re using it to turn muscle building on, and then it’s also going to supply methionine, threonine, and it’s really rich in the other branched chain amino acids too, valine and isoleucine.
If you are turning muscle building on, and then you’ve also got the soybean protein there to provide the building blocks for muscle development, that’s why I use both of them together. Because whey protein is quite expensive compared to soybean, you use it to do its very specific job of turning muscle building on, stopping muscle breakdown, and feeding the muscle. And then your soybean amino acids do the bulk of the rest of the work in actually providing the building blocks for the muscle building process to take place.
ORLA: Okay, that makes sense. So I’m feeding full-fat extruded soy after I ride. I’ve always kept a little bit in the diet every day, but I don’t give them half a kilo every day. He doesn’t need it. Is that okay?
NERIDA: Yeah, so my train of thought has always been, if you have a little bit of the ingredient that you’re going to introduce in larger amounts, the body is robust and ready for it.
With Alay, I’m always wanting her to put on muscle. We weighed her the other day and she’s 30 kilos heavier now than she was this time last year. Just really steadily, which is what we want, and then they maintain that weight when they put it on like that, because it’s been driven by a healthy gut and good quality protein.
With her, I’d give her say 250 grams a day, and then maybe a little bit more after she’s ridden, like increase that to 350 grams. But if you’re only going from a really little bit to half a kilo, I think you’d actually see more benefit if you gave him more consistently and then a little bit more after you ride him.
He can build muscle all the time, it’s just that their muscles are more wired to go, okay, we want to get stronger, after you’ve ridden them. That’s when you put the whey protein in that right-after-riding feed.
But you’re right that as long as you kind of, and this is the best my Friday afternoon brain can do, you don’t want guests showing up on the horse’s small intestinal doorstep without having announced their arrival first.
You have to give the small intestine a heads up on what’s coming, because the pancreas produces the enzymes that the small intestine needs to do the work of cutting up the big stuff into little stuff, because that’s all digestion is. Big stuff that can’t get across the gut barrier, down to little stuff that can pass through without letting bacteria and toxins through.
The pancreas produces those enzymes and secretes them into the small intestine. Because all of those enzymes are protein, if the horse doesn’t have a lot of oil in its diet, there’s no need to be producing lipase enzymes all the time to cut the oil up. When you’re a wild horse trying to survive, they had to conserve everything, particularly through winters and tough environments. So the small intestine will only produce the enzymes it needs to digest what’s present in the diet.
This is why introducing oil slowly is really important. You say to the pancreas, okay, we need this much. And now there’s a little bit more oil, so now you need to produce this much lipase enzyme. I increase it by 60ml every 5 to 7 days for oil, as an example. And any grain-based feed packaging will normally say, introduce slowly into a horse’s diet over a period of 14 days. That’s just to give the small intestine time to adapt.
So probably going from a little bit to half a kilo is a bit extreme. I’d go from maybe 250 grams to maybe 350 grams after you’ve ridden. Or if he doesn’t need that much in his diet all the time, 150 grams daily, then after he’s ridden, go to 300. Something like that.
Enzymes in Horse Feeds and Supplements
ORLA: You said enzyme. And this reminded me, I got asked a whole bunch of times on the road this week about digestive products. A lot of them have enzymes in them, and now everyone is adding enzymes into their feeds. Are we overfeeding them? Are they all the same enzymes from the same company?
NERIDA: A lot of the products don’t actually disclose what and how much enzyme is in them, which makes it hard to tell. But for me, it’s really exciting that enzymes are being added so much, because my PhD research started in 2006, and they’re finally listening.
I’m not the only one, but I’m one of the only ones who’s done enzyme work in horses, because there’s not a lot that’s been done. And genuinely, they are really useful in animal nutrition. There would not be a reputable poultry feed made that does not use enzymes, because chickens are not designed to eat a lot of the grains we feed them. Things like phytate, where a lot of mineral gets bound up and they can’t digest the phosphorus, enzymes solve so many of those problems.
What we think we know for sure in horses, and I’m basing this on looking at lots of fecal pHs in racing horses, because there are thousands of pH measurements now, is that around 25% of horses still have low fecal pH even when we take them to grain diets that should be very digestible in the small intestine and we shouldn’t be seeing starch digestion going on in their hindgut.
Which tells me, and this was where my PhD went, that we can process the grain and remove the barriers to starch digestion by cooking the grain, applying heat and moisture, and in the case of extrusion, also pressure, and we disrupt the starch granule and make it much easier for the amylase enzyme. But what if there’s still a horse barrier to starch digestion? What if they don’t have enough amylase enzyme? And I could see there was research to say that the level of amylase is highly variable between horses.
So we then added amylase and amyloglucosidase, another enzyme, to extruded rice, which is a highly digestible source of starch. And we got an increase in starch digestion. So this is why it’s exciting that companies are adding enzymes, because we can do the best job of processing grains, but you have to process the grain first. The amylase can’t access indigestible starch. If the starch is still bundled up like a golf ball, it’s not digestible, regardless of what enzyme you add.
To answer your question, are we overfeeding enzymes? They’re not really going to get toxic. They’re little proteins. At the levels that they’re being added to products, I don’t see that as an issue. The question is more, if you’ve got a feed that’s already got enzymes in it, do you need to also add a supplement with enzymes? That’s where you’re looking at what products you can take out.
The cool thing with starch-digesting enzymes is you get this double positive effect. You’re getting more complete digestion of starch in the small intestine, which is 30% more efficient than fermenting that starch in the hindgut. And then you’re also not negatively impacting your hindgut microbes. So you’ve got a strong population of fibre-fermenting microbes in the hindgut, and you’re able to fully extract energy from the forages the horse is eating.
Which puts you in this situation where you’re still feeding lots of forage, because horses need lots of forage, but you’re feeding a lot less hard feed. On the farms I work with in Japan, we’ve gone from probably feeding anywhere from 6 to 8 kilos of hard feed a day, down to 3 to 4 kilos. Which is significant when you’re importing most of it.
Diet Analysis, Toxicities, and Trusting Your Nutrition Advice
ORLA: There are a lot of cases, and you’ve dealt with two I think just this last week, that have been formulated by, and I’m going to air quote, nutritionists. And they’ve come back with toxicities.
NERIDA: So we are getting a lot of people using My Happy Horse, which is great, which means I get to do the really cool thing of interacting with a lot of these people and having a look at diets they are planning on feeding.
I had one lady who had been down a familiar rabbit hole for lots of horse owners, in that they’re trying to do the right thing by their horse. Their horse has got a problem, and they keep going and asking for advice from different companies. So she’d been given three diets by three companies, all also selling supplements, so providing nutritional advice but leading her back to using their products. Which is zero issues with that, if the advice is good.
I nearly died when I saw the results. Because these diets were coming with no analysis, they were just coming in as, feed this, this, and this each day. I never give people diets like that, because I want them to be able to see that what I’m recommending is actually balanced.
This lady had very cleverly gone and put all three of those recommended diets into My Happy Horse to get an analysis out. And I nearly died. The first one I looked at, zinc toxicity. Massive. And this horse had hoof problems. So you’ve gone and created a zinc toxicity, which will have also created a copper deficiency, because the copper to zinc ratio would have been, I didn’t even look, but it’d be like thousands to one.
And the poor horse owner is thinking she received advice from someone who’s meant to be qualified to give that advice. The second diet was better in that there weren’t any toxicities, but there were so many deficiencies in it. Deficiencies are in some ways better than toxicities, they’ll cause problems a lot slower, but there were so many nutrients that were really low. And then the third diet, vitamin B1 was through the roof, which, you know, it’s a water-soluble vitamin so it’s typically not seen as being toxic, but I don’t think we know what happens when you feed a vitamin at that level every single day to a horse.
I much prefer to play somewhere in the middle where we know it’s safe. Meet the requirement, but don’t massively exceed it. And then again, heaps of deficiencies in that third diet too.
The point is, when you can’t see what’s in a diet because you haven’t done an analysis on it, you can get led down the wrong path. And in the case of the zinc toxicity, you end up doing more damage. You would have been better off leaving your horse on a deficient diet. Which, neither option is ideal, but it really opened my eyes to how exposed horse owners are to bad advice when they don’t actually have a way of checking how good that advice is.
ORLA: You said it in something you released on Instagram. The most expensive thing a horse owner can do is not trust themselves.
NERIDA: Yes. And you trust all these feed companies, which, I will go into it because now it’ll get back to me, but I trusted a feed company, and they were lying to me for however many years.
ORLA: So, everyone, use My Happy Horse, and it’ll tell you if your feed is actually grain-free or not grain-free.
NERIDA: And there’s been lots of chatter about labelling and feeds labelled grain-free when, quite clearly in the ingredients list, they’re not grain-free. I have no answer to that question, but it is one of the most frustrating things I see feed companies do, and I don’t understand why they do it. If there’s lots of benefit to grain-free products, and I love grain-free products, but they have to be grain-free.
It sounds so stupid when you say it like that, but I said this to someone before. If your newborn baby had colic and couldn’t have most formulas, and you went through all these different formulas and you finally found one that made the baby comfortable, happy, thriving, sleeping, would you ever change that? No, I would never change that. This is what we’re talking about with horses. Metabolic horses that need a grain-free diet. We love that horse just as much as you might love your child. Our horse might cost us a million dollars, or it might cost us $5. Doesn’t matter. We don’t want to kill it because someone has changed an ingredient and not told us.
ORLA: I’ve got such an advantage in this space because it’s so obvious when you read an ingredient list. But I just can’t imagine how devastating it would be to feed a product you thought was safe and have to put your horse down. And I’m not being dramatic, because I’ve seen this happen. Luke Will Smith has been advocating this for years, and I’ve always called him dramatic. I believed the feed company. And so now he’s dealing with the fallout because he’s dealing with their horses that are meant to be grain-free. And I guess it comes back to what you say to people with laminitic horses all the time.
NERIDA: If you have a horse with laminitis and you’ve been managing it for more than a few weeks on a diet, not in the late stages, but at that early stage where something’s not right and the horse is sore but there’s no rotation or anything yet, if that horse is not improving within a couple of days, and definitely if it’s getting worse, there is something not right in the diet. And you need to keep digging.
It could just be the hay. You may have bought teff hay thinking teff is going to be safe, but the teff that was cut this past summer, because of the way the weather was, it was really hard to get low-sugar teff hay, because teff gets stressed and starts storing starch. So it could be that you think the hay is safe, but it’s been stressed around the time it was harvested and it’s not as low in starch and non-structural carbohydrate as you’d think.
Or if you’re feeding a feed, even if the feed says it’s grain-free, go and check carefully to make sure that it actually is grain-free and is actually low in starch.
I opened a bag of a product that should have been safe for my laminitic horse, and it had grain feed mixed through it. I could see that because of what I do. But I was mortified, because I’m like, if that wasn’t me, and it was going to Popcorn, and someone else with a laminitic pony in that early stage of laminitis, right on the knife-edge of which way they’re going to go, if they fed that to their horse, disaster.
There is, by my way of thinking, no reason to label a feed grain-free when it’s not.
ORLA: When is it coming out on My Happy Horse that we’ll actually know if it’s grain-free?
NERIDA: It’s there now, actually. It does it off the ingredient list. If there is any cereal grain, cereal grain byproduct, anything that comes from cereal grain, it will come up red if you’ve said that you don’t want cereal grain in your horse’s diet.
The thing I also want to add is a protein quality rating. So it’ll actually read the ingredient list and give you a sense of what the likely protein quality is in that feed. Soybean will obviously be high, canola meal will be good to moderate, and if anything says specifically cottonseed meal, it’s going to be the lowest. And if it’s just vegetable protein, it’ll probably come up as unknown.
It doesn’t mean those feeds are bad. There are some horses that don’t need a lot of protein, don’t need a lot of essential amino acids. Popcorn is a really good example. She’s so solid and chunky. She doesn’t need really high-quality protein to maintain muscle. She just does it. She’s so thrifty. But if you’ve got a horse you’re trying to build muscle on, or you’ve got a young horse, or a lactating broodmare, then it does become very relevant.
I also want to add a grain starch digestibility rating, so how digestible the starch is likely to be based on processing method and analyses we’ve done over the years.
Stomach pH, Raw Corn, and Omeprazole
ORLA: Raw corn and stomach acid pH. I’m able to check pH levels in the stomach when I’m gastroscoping. I wanted to see what the stomach pH levels are and then what the manure pH coming out looks like. Do we know if those have a relationship?
NERIDA: They’ll have no relationship, because the acid is not coming from the same place. The acid in the stomach will get buffered when it goes into the small intestine, so the small intestine pH is very neutral. And then the acid from the raw corn in the hindgut is from the microbes producing lots of volatile fatty acid and lots of lactic acid.
ORLA: So how long would that pH level drop take? If you put the scope down and a horse had corn in there, it’s not going to change straight away. How long are you talking for the pH levels to change?
NERIDA: It’ll depend on lots of things. Fermentation of grain is pretty fast, so I would think, and this is a stab in the dark, somewhere between half an hour and two hours you would see a difference. And maybe the corn will be gone from the stomach within 2 hours anyway.
The pH of the stomach is so transient, because as food goes in and food goes out, saliva comes in, saliva goes out, it’ll change constantly. Whereas the pH of the hindgut will definitely fluctuate but I don’t think it’ll fluctuate to the same extreme.
ORLA: I was wondering if you had a racehorse in training on a raw grain diet, whether their stomach acid would be quite acidic and their pH would be really low. But I thought there would be, I don’t think you’ll see a difference after a 12-hour fast.
NERIDA: I think what you’ll see is just the pH of the acid being secreted. There might be a difference between horses, but if you do enough of them, you’ll probably see more between-horse variation than between these horses fed this diet and those horses fed that diet. Because they’re all secreting the same acid, it’s all hydrochloric acid. And if they’re being fasted for a certain period of time and they’re not salivating, I would guess their pHs would be pretty similar regardless of diet. But I could be completely wrong.
What would be interesting to look at is horses that have been recently on omeprazole or ranitidine, and see whether they’ve got a lower pH, because they may be hyper-secreting acid.
When you block acid production in the stomach, the parietal cells, the cells that make the acid, when the omeprazole goes and says, nope, you’re not allowed to produce acid, the stomach then goes, we’re meant to be an acidic environment, there’s not enough acid in here, so they actually make more acid-secreting cells. And then the omeprazole comes along and blocks it again, and the stomach panics again and makes more acid-secreting cells. So when you take the omeprazole out, the stomach then has all of those extra acid-secreting cells, and it hypersecretes.
ORLA: To be honest, I thought omeprazole just slowed it down.
NERIDA: It does block it. So if you had your tester that day, the pH should be, provided that horse was actually absorbing the drug, a higher pH than it would have been had it not been on omeprazole. By the time you hit around 24 hours, it’s not complete blocking, but it’s pretty complete when the drug is at its peak in the system.
And then when you take the drug away, the stomach hypersecretes. Which is why a lot of humans can’t come off that drug once they start taking it. My brothers all live on omeprazole because their bodies are under such stress all the time. And when they try to go off it, they get massive acid production and heartburn and stuff. You have to wean off quite slowly.
ORLA: I never thought about people being on it. See, this is why I don’t run marathons. Don’t run. No distance is a record.
NERIDA: I admire marathon runners, I really do, but every year I watch people doing the Irish Marathon, London Marathon, all of that, and I’m like, I can do it! And then I get bored during training and I’m like, no. I’ve said to people, if I ever come home and say I’m going to run a marathon, please book me into some kind of financial institution straight away, because there’d be something really wrong with me.
Anyway, on that note, Orla, thank you very much. It has been a fun Friday afternoon. Whether we made much sense or not, thank you very much for joining us, everyone, and we will catch you in the next episode. Bye!
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