Sugar In Horses' Diets
- Oct 13
- 3 min read
We already know that sugar is a problem for horses with metabolic dysfunction, resulting in insulin resistance, equine metabolic disorder and eventually pituitary pars intermediary syndrome, known as Cushings, and all of these increase the risk of laminitis.
But there is another reason to feed low sugar forages, even if your horse doesn’t suffer from metabolic issues, which is that high sugar forage results in tooth decay, just as it does in humans.
High Sugar vs Low Sugar Forage
A study from Brazil published in August this year in the scientific journal ‘Animal’ followed 20 horses of different sexes ages and breeds - 10 of which were fed sugarcane for 3 years and 10 had Bermuda grass for 3 years as their source of forage.
Not surprisingly, horses on higher sugar grasses had higher incidence of damage to the teeth, resulting in food being trapped, which in turn increases the risk of dental problems.
It was a small sample size, and only forage was considered - not supplements or other hard feeds. However, the results would indicate that high sugar forages are a suboptimal choice of forage compared to lower sugar alternatives for dental health in horses.
You can read more about how horses' teeth function here.
You can read about ageing a horse by its teeth and considerations for dental health in older horses here.
Which forages have lower sugar?
This article compares the qualities of different commonly available hays, including relative sugar levels.
Sugar is not the only hazard in forages. You may remember this study which we covered a few weeks ago talking about relative fungal, chemical and mycotoxin contamination present in horse feeds. This study from Israel looks at toxins in silage, however it's not specific to horses.
But what about fresh grass where sugar levels are variable?
Spring Grass & Metabolic Horses: What You Need to Know
As spring rolls in and pastures turn lush and green, horse owners everywhere who have been paying for high prices for hay over winter breathe a sigh of relief—until they remember the hidden danger in that vibrant grass: sugar. For horses with Equine Metabolic Syndrome (EMS), Insulin Resistance (IR), or a history of laminitis, spring grass can be more threat than treat.
Spring grass is high in non-structural carbohydrates (NSCs)—especially simple sugars. These spike insulin levels and can trigger laminitis in sensitive horses.
Grass Sugar Content by Time of Day
Sugar levels fluctuate dramatically:
Lowest: Between midnight and 10am
Highest: Late afternoon, especially on sunny days
But here’s the catch: If overnight temperatures drop below 5°C (40°F), grass doesn’t metabolise sugars, so even early morning grazing can be risky.
How Much Grass is Too Much?
Research shows horses can consume:
112g/hour on poor pasture
450g/hour on lush pasture
Some ponies have been found to eat 1% of their body weight in just 3 hours—that’s 5kg for a 500kg horse. That’s a massive sugar load.
Remember that the rule of thumb is that horses eat between 1.5 - 2% of their bodyweight in forage each day.
Practical Solutions for Safer Grazing
1. Time It Right
Turn out before 9am, but only if overnight temps stayed above 5°C
Avoid grazing after sunny afternoons or frosty nights
2. Use Grazing Muzzles
Reduce intake by up to 80% while allowing natural trickle feeding
Don’t use muzzles 24/7—horses still need enough forage for gut health.
3. Pre-Graze with Hay
Feed low-sugar hay before turnout to reduce gorging behavior.
4. Encourage Movement
Use track systems or paddock setups that promote walking.
Exercise helps regulate insulin and supports hoof health.
This article compares strip-grazing, paddock paradise and grazing muzzles.
5. Monitor Body Condition
Watch for fat pads on the neck, shoulders, and tail head. These can signal early insulin resistance—even before blood tests confirm it.
6. Mineral imbalances.
Horses looking for minerals will consume more, lick dirt, chew wood. Once you supply optimal minerals, horses tend to eat less. (As an aside we had a client who rejigged their diet according to Sound Advice recommendations - their produce store salesperson asked if one of their horses had died since they were buying so much less feed).
Compare this in humans - if you eat a big steak and fresh vegetables which meet your nutritional requirements you will feel more satiated than eating bags of chips which are empty calories.
Managing metabolic dysfunction isn’t about deprivation—it’s about smart choices. With the right timing, tools, and awareness, your horse can enjoy spring safely.
If you’re unsure about your pasture quality or your horse’s risk level, reach out. We’re here to help you build a grazing plan that’s safe, sustainable, and tailored to your horse’s needs.
You can read more about our recommendations for managing laminitis-prone horses here
Sound Advice is horse-first care. Always. Message us anytime with questions or photos—we love seeing your horses thrive.
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