Sugar occurs naturally in grass, hay and haylage and is an important source of energy. But too much takes its toll on hooves, body condition and metabolism, especially in good doers, which is why you need to know the limit.
A good doer should be below 5‑7 % sugar in the dry matter. If the horse is in regular work where it sweats and gets out of breath, it can tolerate up to 10 %.
Measured on the horse itself: 0.5‑1 g sugar per kg bodyweight per day. More than 2 g per kg per day causes illness. So a 400 kg good doer is best kept at 200‑400 g of sugar a day.
How much sugar per day
Your horse's weight
Tolerates (0.5‑1 g per kg)
Causes illness above (2 g per kg)
300 kg
150‑300 g
600 g
400 kg
200‑400 g
800 g
500 kg
250‑500 g
1.000 g
600 kg
300‑600 g
1.200 g
The sugar comes mainly from grass, haylage and hay.
Signs of too much sugar
Laminitis or a tendency to sore hooves
Excess weight and fat deposits, typically on the neck or tailhead
Metabolic problems such as EMS or PPID
Unsettled gut and poor digestion
High insulin, or low energy despite plenty of feed
If the horse is a good doer or on the round side, assume the sugar is too high
Mix straw into the forage to lower the total sugar
Limit grazing time in spring and autumn, and after cold nights
Use a grazing muzzle or shorter grazing time if your horse is turned out all day
Keep an eye on treats, apples and carrots, small amounts soon add up
Want to know more?
Work out the sugar in your own forage
A forage analysis shows the sugar percentage in your hay or haylage. From there it's simple maths: amount times dry matter percentage times sugar percentage.
Example with 7 kg haylage at 75% dry matter, i.e. 5.25 kg dry matter:
At 17% sugar, that gives 892 g of sugar a day, which is far too much. At 7% sugar, it gives 368 g, which keeps you within the limit for a 400 kg good doer.
An analysis is the only way to know how much sugar your horse is really getting. Ask the supplier of your batch for one, or send in a sample yourself. New figures with every new batch.
Sugar and workload
Good doers and ponies: no more than 5‑7 % sugar in dry matter. Horses in regular work where they get out of breath and sweat: up to 10 %.
As a practical precaution, we recommend 0.5‑1 g of sugar per kg of bodyweight per day; this is not a fixed clinical limit. Over 2 g per kg per day leads to illness. The less work your horse does, the tighter you need to keep it, because sugar that isn't used as energy ends up as imbalance.
Grass, treats and the hidden sources
The sugar in grass fluctuates over the season. Spring and autumn are the critical periods, and the content rises especially after cold nights. Limit turnout during those periods, or use a grazing muzzle so your horse can still go out with the herd.
Treats, apples and carrots count too. Small amounts are fine, but they quickly add up when they come on top of forage that is already high.
Selected articles from the knowledge bank
What happens when a horse gets too much sugar? · How much sugar does your horse get from grass? · Cresty neck in horses, the most important warning sign you would do well to learn to spot · Straw for horses, a solution when the forage contains too much sugar
