Why Feed Type Matters for Temperament
Horses are fundamentally herbivores adapted to eat forage — largely fibre — over many hours a day. Their digestive system and metabolism evolved accordingly.
- Their stomach is small and empties frequently, then the bulk of digestion happens in the hindgut, where specialized microbes ferment fibre into volatile fatty acids (VFAs) to provide energy.
- In contrast to forage, grains and high-starch/sugar concentrates introduce rapidly digestible carbohydrates (starch & sugars) that the small intestine absorbs quickly, causing glucose and insulin spikes.
- These different digestion pathways can have major effects on gut health, metabolism, behaviour and temperament.
Thus, what we feed and how can influence more than just body condition: it can affect reactivity, calmness, stress, and long-term welfare.
Forage vs Grain vs Fat: Comparing Key Diet Types
Forage-Based Diets (Hay/Pasture/Good Quality Roughage): Benefits for Calm Temperament and Gut Stability
- For most horses, free-choice hay or pasture forage is ideal.
- Forage provides slow-release energy, promoting stable blood sugar and steady digestion.
- Behaviourally, horses on fibre-based diets tend to be calmer, more settled, and less reactive. A controlled study comparing high-fibre (HF) vs high-starch (HS) diets showed significantly lower heart-rate reactivity in HF-fed horses during handling tests.
- In that same study, “settled behaviour” and more relaxed responses to stimuli were linked to fibre diets.
Best for: leisure horses, older horses, easy-keepers, nervous or “hot” horses, horses with sensitive digestion or metabolic issues, and horses not doing heavy work.
High-Starch/High-Sugar Grain-Based Diets (Oats, Corn, Barley, Sweet-Feeds/Concentrates): Behavioural Reactivity and Health Risks
- Grains supply dense, immediate energy — useful for performance horses needing bursts of fuel.
- But they also carry trade-offs: Grain supplements may cause an overload of starch, affecting a healthy metabolite-hormone response, while undigested starch often reaches the hindgut, upsetting microbial balance — This can lead to gut disturbances, metabolic issues, or digestive disorders. Grain concentrates have been associated with colic, laminitis, gastric ulcers, rhabdomyolysis and developmental orthopaedic disease.
- Behaviourally, this has been correlated with increased reactivity, “hotness,” nervousness, unpredictability. In the cross-over study of naïve ponies, high-starch diets produced more reactive behaviours (e.g. increased pace-change, higher reactivity scores) compared to fibre diets.
- In young horses, especially after weaning, conventional high-grain diets have been linked to a higher incidence of stereotypic behaviours (e.g. cribbing, wind-sucking, wood-chewing) compared to low-starch/fat-fibre diets. Horse Journals+1
Best for (but with caution): high-performance horses — but only if grain feeding is carefully managed; otherwise, grain can make horses “hot,” reactive, or even prone to digestive/metabolic disorders.
High-Fat and Fibre Diets (Fat supplements, Beet Pulp, Low-NSC Concentrates): Cool Energy and Improved Digestive Health
- Fat offers a calorie-dense, yet slow-release energy source. Fat provides more than double the calories per gram compared to carbohydrates, and energy from fat is metabolised steadily, avoiding the peaks and troughs associated with starch-driven glycemic swings.
- Fat and fibre diets are frequently recommended — especially for horses that need calories but tend to get “hot.” Many horse-owners and equine nutritionists report that fat-supplemented diets lead to calmer behaviour, less spookiness, better focus, and fewer “sugar highs.”
- In addition to behaviour benefits, fat + fibre feeds support gut health, reduce risk of hindgut acidosis, and generally align more closely with natural equine digestive physiology.
Best for: horses needing extra energy (e.g. endurance, light-to-moderate work, weight maintenance) but prone to excitability; older or metabolic-sensitive horses; and “hot” temperaments needing “cool” calories.
How Age, Workload, Sex and Temperament Influence Feed Response
Feed effects aren’t universal. A horse’s age, workload, temperament, and sex all play a role in how they react to diet. Some of the most relevant research:
- In a study of adult vs aged mares fed either forage-only, starch/sugar-rich, or oil/fibre-rich concentrates, aged mares showed decreased insulin sensitivity, regardless of diet.
That suggests older horses may be more prone to metabolic issues, making them more sensitive to high-starch diets — and making a fibre/fat-based diet more appropriate.
- For young, growing horses and foals, while grain-based diets are commonly used to meet high energy and growth demands, a recent 2025 study on weaned foals showed that different grain types — and their starch digestibility — greatly influence glycemic responses, digestibility, and hindgut fermentation parameters. Too much undigested starch reaching the hindgut may pose longer-term digestive health risks even in young horses.
- When it comes to workload/activity levels: high-performance or heavily-worked horses may benefit from some grain or processed feeds to meet energy demands; but balancing with fibre and fat — and avoiding excessive starch — helps prevent the “wired but brittle” behaviour in sensitive horses.
- Sex and temperament are less studied, but many older studies and practitioners note that certain horses (mares, stallions, geldings) cope differently with high-energy feeds, especially when combined with stress or training load — reinforcing the need for individualised feeding based on horse history, health and temperament.
Scientific Evidence on Diet, Behaviour and Welfare
Behavioural Reactivity & Gut-Brain Connection
A key study titled “High-starch diets alter equine faecal microbiota and increase behavioural reactivity” compared naïve ponies fed a high-starch (HS) vs high-fibre (HF) diet. HS ponies were more reactive, less settled; HF ponies displayed calmer, more exploratory behaviour.
This suggests the gut-brain axis — long known in other species — may play a role in equine temperament too. Changes in hindgut microbial communities triggered by diet may influence mood, stress and behavioural reactivity.
Gut Health, Digestive Stability & Long-Term Welfare
A high-starch diet alters the physical and chemical environment in the horse’s gut. A 2021 study comparing HS vs HF diets in young stall-fed horses found that HS diet horses had altered gut particle sizes and greater volatile fatty acid production — signals of disrupted gut health
Behavioural Problems & Stereotypies (Cribbing, Wind-Sucking, Anxiety)
Horses on low-fibre / high-starch diets — especially young horses after weaning — have been shown to be more prone to develop stereotypic/redirected behaviours like cribbing, wind-sucking, or wood-chewing. Such behaviours are often signs of stress, gut discomfort, or unmet behavioural needs, and literature suggests diet is a significant contributing factor (alongside management, environment, social housing, etc.).
Practical Feeding Guidelines for Different Types of Horses
For in-depth guidance on optimal horse feeding (HorseTVGlobal): https://www.youtube.com/watch?v=d74dsbz7dfQ
Based on research and welfare considerations, here are practical guidelines for feeding depending on what your horse is like.
| Situation / Horse type | Recommended Feeding Strategy / Diet |
| Leisure horse, little or no work, nervous/twitchy temperament | Mostly forage (good hay/pasture), with optional fat- & fibre-based concentrates if extra calories needed; limit grains. |
| Performance horse (eventing, jumping, endurance, dressage) with high energy demand | Balanced approach: high-quality forage as base; limited grain or starch only when needed; consider fat & fibre to supply sustained energy; manage starch intake carefully. |
| Young growing foal or weanling | Use appropriate concentrate if needed, but monitor starch digestibility and avoid overfeeding grain to prevent hindgut issues; ensure adequate fibre. |
| Aged horse, senior maintenance | High fibre + fat, low starch, avoid sudden diet changes, monitor metabolic health (insulin sensitivity issues possible). |
| Horses prone to excitability, anxiety, or “hot” temperaments | Avoid high-starch/sugar concentrates; prefer fibre- and fat-based diets; feed smaller meals, provide consistent forage access to avoid glucose/insulin spikes or hunger-stress cycles. |
| Horses vulnerable to digestive disorders, colic or laminitis, or with metabolic conditions
| Minimise grain, avoid high NSC (non-structural carbohydrates), prioritise fibre + fat; feed small frequent meals; provide free access to forage (water + salt/minerals). |
Why Many “Behavioural Issues” Are Nutrition-Related (Not Just Training or Temperament)
It’s becoming clear that many behaviours commonly attributed to “bad temperament”, “spookiness”, “naughtiness” or “lack of training” might actually be driven — at least in part — by diet and gut health.
- Rapid sugar/starch-driven spikes in blood glucose and insulin may trigger excitability, nervousness, and restlessness.
- Disrupting the hindgut microbiome via starch overload can lead to gut discomfort, altered gut-brain signalling, stress, and poor digestion, which may manifest as anxiety or behavioural aberrations.
- Underfeeding forage (i.e. limited access to roughage) leaves horses with unnatural starvation cycles, increasing stress, frustration, and stereotypic behaviours.
So often, the “wrong” behaviour may not be training- or character-based, but nutrition- or management-based.
Considerations & Cautions from Veterinary and Scientific Viewpoints
- Sudden changes in diet (especially increasing grain/starch) can disrupt gut microbial balance, increasing risk of colic, laminitis, metabolic disease, and behavioural changes.
- Over-relying on high-starch concentrate increases the risk of metabolic disorders such as insulin resistance, obesity, and developmental orthopaedic disease (in growing horses).
- Behaviour studies generally show better welfare outcomes (less reactivity, more natural behaviour) when horses are given fibre-based diets and free access to forage, plus stable social and environmental conditions.
- Every horse is different: age, sex, breed, individual temperament, workload, health history — all these factors modulate how a given diet affects them. There’s no one-size-fits-all.
Conclusion — Feed is More Than Calories: It Shapes Temperament, Health & Welfare
Feeding a horse isn’t just about delivering calories or meeting performance needs. The type of feed — forage-heavy, grain-rich, fat-supplemented — can strongly influence temperament, reactivity, behaviour, long-term gut health, and welfare. Modern research (gut-microbiota studies, behavioural reactivity tests, welfare assessments) increasingly supports what many traditional horsemen have observed: a diet closer to what nature intended (fibre + fat) tends to produce calmer, healthier, more stable horses.
That said, performance demands, growth phases, or individual metabolic requirements sometimes necessitate more concentrated energy — but this should be done mindfully, with moderation, and always preserving adequate fibre and forage access.
Frequently Asked Questions
1. How does horse feed affect behaviour and temperament?
Horse feed directly influences behaviour through its effects on blood sugar, insulin, and the gut microbiome. High-starch feeds can increase excitability and reactivity, while high-fibre and fat-based diets help promote calmer, more stable behaviour.
2. Why do high-starch horse feeds make some horses “hot” or reactive?
High-starch grains create rapid spikes in glucose and insulin, which can trigger excitability, tension, and unpredictable behaviour. Excess starch that reaches the hindgut also disrupts microbial balance, further affecting mood and stress responses.
3. What is the best feed for a calm horse?
A high-fibre, low-starch diet is best for calm behaviour. Free-choice forage, beet pulp, chaff, hay, and fat-and-fibre concentrates support steady energy release and maintain a balanced gut microbiome, resulting in a quieter temperament.
4. Does fibre help horses stay calm?
Yes. Fibre is digested slowly and steadily, preventing sugar highs and gut discomfort. Research shows that horses on high-fibre diets demonstrate lower heart-rate reactivity and more settled behaviour than those on high-starch diets.
5. Is grain bad for horses?
Grain isn’t inherently bad, but high levels of starch can cause digestive issues, metabolic stress, and behavioural reactivity. Grain should be fed cautiously, especially to nervous, metabolic-sensitive, or lightly worked horses.
6. What is the safest diet for horses prone to colic, ulcers, laminitis or metabolic disease?
A low-starch, high-fibre, high-fat diet is safest. Free-choice forage, low-NSC feeds, and small frequent meals reduce gut disturbances and help stabilise blood sugar, reducing the risk of digestive and metabolic disorders.
7. How does the gut-brain axis affect horse behaviour?
Changes in hindgut bacteria — especially from starch overload — influence stress hormones, mood, and behavioural reactivity. Studies show that modifying the gut environment through diet affects calmness, focus, and stress responses.
8. Should performance horses be fed grain?
Performance horses may need some grain for energy, but starch intake should be controlled. Combining moderate grain with high-quality forage, fats, and fibre provides sustained energy without making the horse “hot” or sharp.
9. What is the best diet for older horses?
Senior horses benefit from high-fibre, low-starch diets with added fat. Older horses often have reduced insulin sensitivity, making them more prone to sugar-related metabolic issues, so fibre- and fat-based calories are preferable.
10. Why do some young horses develop stereotypic behaviours like cribbing or wind-sucking?
Low-fibre, high-grain diets increase stress, gut discomfort, and altered gut motility — all factors linked to the development of stereotypies. Young horses fed high-fibre, low-starch diets show fewer repetitive or stress-related behaviours.
11. How does diet influence a horse’s reactivity and spookiness?
High-starch diets promote quick-release energy and fluctuating blood sugar, increasing reactivity and tension. Diets rich in fibre and fat provide “cool energy,” supporting calmer, more focused behaviour under saddle.
12. Can feeding more hay improve a horse’s behaviour?
Yes. More forage reduces stress, prevents hunger cycles, stabilises gut fermentation, and supports natural behaviour. Many behaviour issues improve simply by providing ad-libitum hay or pasture.
13. What is the best feed for a nervous or anxious horse?
Choose feeds that are low in starch and high in fibre and fat. Avoid sweet feeds, corn, barley, and oats. Focus on hay, beet pulp, alfalfa, chaff, and oil- or fibre-based concentrates to maintain calmness and reduce reactivity.
14. How quickly can diet affect horse behaviour?
Behaviour can change within days to weeks depending on gut microbial shifts, blood sugar stability, starch load, and stress reduction. Full gut-microbiome adaptation typically takes 2–4 weeks.
15. Is a forage-only diet enough for most horses?
For many leisure, lightly worked, or metabolically sensitive horses, yes. Forage often provides sufficient calories and supports calm behaviour. Horses with high workloads may need additional fat, fibre, or controlled starch.
References
- https://www.msdvetmanual.com/management-and-nutrition/nutrition-horses/feeding-practices-in-horses-and-other-equids
- https://esc.rutgers.edu/fact_sheet/the-basics-of-equine-nutrition/
- https://www.sciencedirect.com/science/article/abs/pii/S016815911500026X?
- https://www.ivis.org/library/reviews-veterinary-medicine/carbohydrate-metabolism-horses
- https://www.nature.com/articles/s41598-019-54039-8
- https://www.sciencedirect.com/science/article/abs/pii/S0168159109000355
- https://pubmed.ncbi.nlm.nih.gov/29356053/
- https://link.springer.com/article/10.1186/s12917-025-04716-w
- https://feedmark.com/Jen/Jen-2021-01.pdf
- https://www.horsejournals.com/horse-care/feed-nutrition/effect-diet-equine-stereotypic-behaviours
