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Integral Equine Nutrition

Integral Equine Nutrition offers independent, evidence-based feeding advice. Specialising in on-site

Integral Equine Nutrition is run by Sophie Fletcher, BAnVetBioSci (Hons I), MAnSc, and aims to optimise your horses health, well being and performance through correct nutrition. Advice is both practical and science-based, as Sophie has been involved in both horses and research science for many years.

17/10/2025

Yesterday's post seems to have been quite popular! I made quite a few comments that I claimed were backed up with research, and particularly as what I'm saying is a little controversial, I thought I would dig up some of the studies I'm referring to (and this isn't all of them).

Most of the time when people (experts) say that obesity causes insulin resistance/laminitis they refer back to larger scale field studies that find that obesity is linked with insulin levels going up/resistance or laminitis. But this doesn't tell us which came first! So as someone who was trained in basic experimental research, I look to the controlled experiments where horses were overfed caloriess to induce obesity, to look for the chicken and the egg - results below.

Warning. Long.

NOTE: I have read all of these studies in full at various points in time, but I admit that I have used AI tools to put it together and compose this post because I simply did not have time to do it all myself! Image is my brain trying to organise it into an easy to understand format and failing :P

🧁 When insulin does change — it’s about diet, not just body fat

Carter et al. (2009, AJVR 70:125–132)
When horses were fed double their energy needs on a sweet feed that was over 30 % sugar + starch, they put on about 20 % body weight and their insulin sensitivity dropped.
→ The issue wasn’t “being fat” — it was the high-starch diet driving the change.

Silva et al. (2020, Pesq Vet Bras 40:1–9)
Horses on a grain-heavy, high-calorie ration showed insulin dysregulation after 3 months — then went back to normal once their metabolism caught up, even though they were still obese.
→ Again, the problem was what they were eating, not just how big they got.

🌾 When insulin doesn’t change — even with weight gain

Bamford et al. (2016, EVJ 48:368–373)
Horses and ponies fed a high-fat, low-glycaemic diet for 20 weeks became properly round (BCS ≥ 7) but stayed insulin-sensitive.

Lindåse et al. (2016, AJVR 77:300–309)
On a forage-plus-fat diet fed at 2½ × maintenance, insulin sensitivity didn’t budge during weight gain — and improved by more than 50 % once they went onto pasture.

Nostell et al. (2020, EVJ 52:368–373)
Obese mares (BCS > 7) on haylage + fat kept normal insulin sensitivity but had higher blood pressure and cortisol. So obesity affected circulation, not metabolism.

Blaue et al. (2019, Dom Anim Endocrinol 69:1–11)
After one to two years of moderate-starch overfeeding, most ponies and horses stayed metabolically normal. Only three developed insulin dysregulation — and laminitis showed up only in those individuals.

⚖️ The takeaway

Across all these studies, insulin issues showed up only when diets were high in sugar and starch.
Feeding more calories from fat or forage made horses fatter, sure — but didn’t make them insulin-resistant.
And laminitis occurred only when true insulin dysregulation developed, not simply because the horse was overweight.

👉 So far, research hasn’t found a causal link between “being fat” and insulin resistance or laminitis — it’s the diet composition that matters most.

16/10/2025

LAMINITIS PREVENTION

It’s not about body fat. It's not even about grass.
It’s about insulin.

Yes, body fat and "lush" grass intake often show up in laminitic horses—but they’re not the cause. Hyperinsulinemia is. I’ve seen this with my own eyes, during professional experience in undergrad with the Pollitt research group—where laminitis was experimentally induced by high insulin alone, in lean STB horses, with no access to grass. If you want to prevent the most common form of laminitis, you need to focus on what’s driving it—not just what’s visible.

Fat is more often a symptom or indicator in insulin dysregulated horses—not the root cause. Some overweight horses stay metabolically normal (and therefore laminitis-free), especially on low sugar/starch diets (and there is scientific evidence to support this). Some lean horses are insulin resistant and suffer terribly with laminitis despite perfect condition. That tells us fat is a risk marker, not a reliable trigger. The research around adipose tissue (fat) and inflammatory products is very contradictory in horses and there is no clear link between inflammation and insulin in horses to date - so let's stick to what we DO know.

Based on what we currently know, reducing insulin usually means keeping sugars and starches low across all parts of the diet, which will often result in fat loss also. Lower sugars --> lower insulin --> lower fat NOT the other way around.

Grass can be a factor, yes—but it's just one piece of the metabolic puzzle. And if you follow this page, you'll know that grass is not always high in sugar. I personally caused a flare up in Hakon's first bout of laminitis by assuming the grass the problem, taking him off it and feeding more hay. Turned out the hay was too high in sugar, and the grass was fine.

In most cases, keeping the diet low sugar/starch will do the trick, but we also have to acknowledge that not all cases respond to diet. Some horses remain laminitis-prone with high insulin despite doing everything “right”—which means there are other triggers at play that we don’t yet fully understand. It’s likely multifactorial, especially for these outliers. There are many other things that raise insulin (transport, stress, corticosteroids, pregnancy, hormonal conditions and season are among those we know of) who knows what other environmental/plant components might do the same?

So if you want two ways to prevent laminitis...

1. Reduce insulin.
2. Reduce insulin.

How you do that depends on your context.

15/10/2025

Spot the difference?

Two of our paddocks, next to each other, both have the same grazing management and have had a similar amount of rest.. but the first one is taking longer to "wake up" after winter, with shorter plants.

It also has less diversity than elsewhere on the property.

The likely reason? Compaction from driving - this paddock is right next to our manure piles, so tends to get manure spread on it more often, and particularly when it's too wet to get to other areas - heavy vehicles smooshing down soggy ground = more compaction.

13/10/2025

When it fits like a glove in the recycled box 👌🔥

09/10/2025

Nice to see a negative result published (this can be a problem in science - positive results are more interesting and get published more often, but it's equally important to know when there is no effect!).

We know that replacing starch calories in a horse's diet with fat calories lowers reactivity, but this recent study shows that the type of oil doesn't make any difference to the behaviour in an acute setting, which is not really a surprise, but good to know!

Both of these oils were high in omega 3 fatty acids though... given that omega 3 fatty acids are associated with positive mental health outcomes in humans, it would be fascinating to look at a much longer term study looking at omega 3 intake and behaviour more generally...

Study is open access to feel free to search the title and read it yourself :)

Hartwig, Samantha, et al. "The effects of a plant-based and a plant-and marine-based n-3 oil supplement on behavioral reactivity, heart rate variability, and plasma fatty acid profile in young healthy horses." Journal of Animal Science 103 (2025): skaf117.

Lay Summary
Reactive behaviors in horses can impact the welfare and safety of both the horse and the handler. Reductions in reactivity have been observed
in horses-fed diets with increased fat and low starch and sugar, but the effects of specific fatty acids on reactive behaviors in horses is unknown.
Therefore, the objective of the study is to investigate the impacts of camelina oil (providing the plant-based α-linolenic acid, ALA) and a mix of
camelina and algae oil (providing the marine-based eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA) on plasma fatty acids, heart
rate variability, and reactive behaviors. Horses were supplemented with either camelina oil, a camelina and algae oil mix, or water (control) for
6 wk. All horses underwent a novel object test and plasma fatty acids, heart rate variability, and reactive behavior was assessed before and after
supplementation. Plasma fatty acids were largely reflective of the oil consumed, however, heart rate variability and behavior did not differ among
groups. Results suggest that supplementation with either camelina oil or a camelina and algae oil mix may not be effective in reducing reactive
behaviors in otherwise healthy horses not experiencing chronic stress.

08/10/2025

When your horse is being silly (or cranky, or scouring, name your problem!)… everyone’s got a theory.

“It’s the sugar in the spring grass.”
“No, it’s the potassium.”
“Too much protein.”
“Not enough work.”
“Hormones.”

There’s always an (often very strongly held) explanation floating around. And sometimes it’s right, sometimes it’s not.

It’s part of what makes horse nutrition tricky. There’s so much overlap between diet, behaviour, hormones, gut health, weather, management… and no single “right” answer.

That’s why I put together my mini course — to help people make sense of all this stuff and understand how the different parts fit together, and be able to make better informed decisions for their own horses.

It’s short, practical, very affordable and designed to help you see why things happen, not just what to feed.

Link in comments!

07/10/2025

Human microbiome researcher Tim Spector often talks about aiming for 30 different plants per week to support gut diversity and overall health. Apparently, this variety has a bigger impact on our health than all other major diet factors.

When I first heard that, of course my brain went straight to horses (after counting up how many plants I'd eaten!).
They’re obviously herbivores and limited to plants only (usually...), but most horses actually eat a very limited range of plants.

A typical horse might graze a paddock dominated by kikuyu or ryegrass, maybe a bit of clover, eat one or two types of hay or chaff, and a couple of feed ingredients. That’s often fewer than ten plant species — and the same ones, every single day.

Encouraging more diversity in pasture (even just through good management and rest, not necessarily seeding) can unlock a huge variety that’s already waiting in the soil seed bank. It also gives horses more freedom to choose what they need.

And if your horse’s world is mostly hay and a bucket feed, even small additions — a few forage herbs, some safe fruit and vegetable treats, a few different types of hay — can add some of that missing variety.

So I’m curious… have you ever thought about how many different plants your horse actually eats each week? Would you be interested in increasing it?

06/10/2025

How clever are my parents!

While I was mostly out of action last week with a mild but annoying cold hitting my household, they were busy coming up with a neat hay feeder idea (and many other property management tasks that are probably more important but less interesting to share :P)

I have scoured the internet high and low for long feeders suitable for sharing in the shelter and couldn't find much that was suitable (or wasn't extremely $$$$).

But here we go - shade cloth and some old fence rails seem to be doing the job perfectly - fine dust can drop through the bottom and I can't see any safety issues.

We've done this because as of a few days ago, all three horses are now sleeping out in the dry lot (summer camp!) together. They come in for an hour or so to eat their individual feeds, lucerne and teff hay, then out they go with rhodes grass hay for the rest of the night. We'll see how it goes!

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