By: Dr Rosie Alcorn BVSc PG Cert VPS Cert AVP MRCVS
With increasing awareness of equine metabolic conditions and the role of diet in managing them, one rule we frequently encounter is:
“My horse’s diet needs to be less than 10% starch and sugar.”
But what does this actually mean - and why is it recommended?
Low starch diets are often advised for horses with conditions such as:
Equine Metabolic Syndrome (EMS)
Polysaccharide Storage Myopathy (PSSM)
Gastric ulcers
Laminitis
And other metabolic or behavioural concerns
In truth, it’s not just starch we need to look at, but the total non-structural carbohydrates (NSC) — which include both starch and sugar.
These components are known for providing quick-release energy, which can cause problems in metabolically sensitive or highly-strung horses. Think of it like feeding children too many sweets — the results can be dramatic!
Research and clinical experience suggest that a diet containing less than 10% starch and sugar (NSC) is often beneficial for managing these conditions.
Feeding forage and concentrates that together contain less than 10% NSC can help to:
* Stabilise blood sugar and insulin levels
* Prevent excess starch and sugar from reaching the hindgut, protecting the gut microbiome
* Reduce excitable or reactive behaviour in some horses
This 10% threshold is supported by decades of research and clinical case studies, where significant improvement has been seen through dietary changes alone.
Percentages vs. Feed Weights
Here’s where it gets practical.
Most nutritional information is listed as a percentage, but horses don’t eat percentages — they eat kilograms of feed. So, to know how much actual starch and sugar your horse is consuming, we must convert those percentages into real weights.
Don’t Forget Forage, Treats & Supplements
You must account for all sources of NSC in the diet, including:
Forage (hay, haylage, grass)
Hard feed (mixes, cubes, balancers)
Treats and extras
Simple NSC Calculation Formula
Nutrient weight (kg) = Amount of feed fed (kg) × (Percentage of nutrient / 100)
This will give you the actual kilograms of starch and sugar your horse is consuming.
Example: Calculating NSC Intake
Let’s say we have a 500 kg horse, and we’re feeding:
10 kg of hay at 10% NSC → 10 × 0.10 = 1 kg of starch/sugar
1 kg of feed at 50% NSC → 1 × 0.50 = 0.5 kg
Total NSC = 1.5 kg
Total feed = 10 + 1 = 11 kg
NSC % of the total diet = (1.5 / 11) × 100 = 13.6%
This is above the 10% threshold and may pose a risk for sensitive horses.
Understanding how to calculate NSC allows you to make informed decisions - especially when managing horses with:
Laminitis
Ulcers
EMS
PSSM
It also highlights why you must consider the amount fed, not just the percentage on the label.
For example:
A balancer with 15% starch, fed at 0.5 kg/day
→ 0.5 × 0.15 = 0.075 kg of starch
A feed with 12% starch, fed at 4 kg/day
→ 4 × 0.12 = 0.48 kg of starch
Despite a lower percentage, the second feed delivers more total starch.
For horses with metabolic or gastrointestinal issues, recommended guidelines are:
* Per meal: Less than 1g of starch per kg of body weight
→ For a 500 kg horse = max 500 g of starch per meal
* Total diet: Less than 10% NSC (starch + sugar), by weight
Feeding a diet containing less than 10% starch and sugar is a key strategy in managing equine health conditions. By:
Selecting appropriate forage and hard feed
Analysing NSC content
Calculating actual intake in kilograms
…you can support your horse’s wellbeing and reduce the risk of issues like laminitis, ulcers, and insulin resistance.
For best results, work alongside an equine nutritionist or veterinarian to tailor your horse’s diet and make ongoing adjustments as needed.
Pink Mash contains less than 2% sugar and starch so you can feed with confidence, knowing your horse's diet won't be exceeding 10%, as long as the product you are feeding alongside, combined with the forage they are eating, doesn't equal more than 8%.
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