When it comes to feeding horses, especially those in regular work, the conversation often revolves around grains, supplements, and performance enhancers. But what if the key to better digestion, sustained energy, and overall wellness lies in something simpler - oil?

Oil, or dietary fat, is emerging as a powerful tool in equine nutrition. Not only does it offer a dense source of energy, but it also supports digestive health.

Understanding Equine Energy Needs

Horses require energy to fuel movement, maintain body condition, and support metabolic functions. The source of that energy matters, especially when balancing performance with health.

Types of Work and Energy Demands

Light Work (e.g., trail riding, pleasure riding): Primarily aerobic, relying on oxygen to metabolise fat and fibre.
Moderate Work (e.g., campdrafting, show jumping): A mix of aerobic and anaerobic metabolism, requiring both fat and carbohydrate sources.
Heavy Work (e.g., cutting, reining, polo): Short, intense bursts of anaerobic activity, fueled by stored glycogen and glucose.

*Aerobic work uses oxygen to convert fat and fibre into energy during sustained, low to moderate-intensity activity, while anaerobic work relies on stored carbohydrates for quick bursts of high-intensity effort when oxygen supply is insufficient.

The Grain Problem

Grains are rich in carbohydrates, which provide quick energy. However, when fed in large amounts, they can overwhelm the horse’s digestive system:

Starch Overload: Undigested starch reaching the hindgut can ferment, causing acidosis.
Digestive Disturbances: Increased risk of colic and sub-clinical laminitis.
Behavioural Effects: Some horses become excitable or anxious on high-grain diets.

To reduce these risks, grains must be carefully processed and balanced with fibre and fat. But there’s a better alternative…

The Science of Fat in Equine Diets

Recent research shows that adding oil to the diet offers a safer, more efficient and highly digestible energy source for horses across all workloads. Oil also supports aerobic training and, with time for metabolic adaptation, enhances muscle glycogen storage, critical for anaerobic bursts. Horses performing high-intensity work rely first on blood glucose, then on stored glycogen; when these deplete, fatigue sets in. A diet enriched with fat not only provides concentrated energy but also helps preserve glycogen and stabilise blood glucose levels, delaying fatigue. This makes oil an ideal addition to the diets of performance horses, improving stamina, recovery, and overall performance while reducing the need for high-grain feeding.

Here’s why oil deserves a place in your horse’s feed bin:

**High Energy Density**

Oils deliver nearly three times more energy than grains, meaning just 330 ml of oil provides the same energy as 1 kg of oats, without triggering ‘hot’ behaviour or increasing the risk of hindgut acidosis (see Table 1).

Supports Digestive Health - Unlike starch, fat doesn’t ferment in the hindgut, making it gentler on the digestive system. Fat is digested in the small intestine, reducing the risk of hindgut fermentation and associated issues like acidosis and colic.

Enhances Metabolic Efficiency - Feeding oil trains the horse’s metabolism to use fat during aerobic work, preserving glycogen stores for high-intensity efforts.

Reduces Grain Dependency - By replacing part of the grain ration with oil, you lower the risk of digestive upset while still supporting energy needs.

Benefits of Oil Supplementation

Behaviour and Temperament
Oil provides a steady, non-starch energy source that helps reduce excitability and reactivity in horses, including weanlings and those prone to tying-up. Horses on oil-enriched diets show calmer behaviour, reduced startle responses, and lower salivary cortisol levels. This calming effect supports better learning, handling, and overall mental stability, especially important for young or sensitive horses.

Improved Stamina
Oil supplementation increases resting muscle glycogen concentrations, allowing horses to preserve blood glucose and delay fatigue. While oil doesn’t increase peak performance, it enables horses to maintain effort for longer periods. This “glucose-sparing” effect is especially beneficial for disciplines requiring sustained anaerobic output, such as cutting, racing, and eventing.

Reduced Heat Production
Up to 75% of muscular energy is lost as heat during exercise. Oil reduces total body heat production by as much as 14%, which lowers the need for sweating and conserves fluids and electrolytes. This is particularly valuable for horses working in hot or humid climates, where heat stress and dehydration are major concerns.

Lower Heart Rate and Stress
Horses fed oil-enriched diets show lower heart rates and cortisol levels during work, indicating reduced physical and psychological stress. In studies of young Quarter Horses, those supplemented with oil recovered faster and performed more calmly during reining and cutting exercises. Lower heart rates at the same workload reflect improved efficiency and reduced strain.

Immunity and Inflammation
Oil can help protect against gastric ulcers, especially in horses under stress from training, travel, or competition. Just 45 ml of corn oil daily has been shown to reduce gastric acid secretion, offering a simple dietary strategy to support gut health. There is considerable evidence that omega-3 oils reduce inflammatory reactions in joint disease in humans. Recent international equine research indicates that similar responses may be expected in horses

Fertility and Growth
Because oils contain no protein, vitamins, or minerals, diets must be carefully balanced, especially for growing horses and breeding mares. However, when properly managed, oil supplementation supports fertility and healthy development by providing concentrated energy without digestive strain.

Weight Management and Gut Fill
Oil provides high energy with low bulk, reducing gut fill and overall weight load, an advantage in racing and endurance disciplines. This lighter digestive load can improve speed, agility, and recovery while maintaining body condition in horses that lose their appetite under stress.

Choosing the Right Oil

Most horse diets today are based on cereal grains, which are naturally high in omega-6 fatty acids. In contrast, horses in their natural environment, grazing and browsing, consume a diet rich in grasses and forages that provide a much higher proportion of omega-3 fatty acids. This imbalance matters: polyunsaturated fatty acids (PUFAs) from sources like corn, sunflower, safflower, soybean, and rice bran oil are predominantly omega-6, which can promote inflammation when consumed in excess. On the other hand, oils rich in omega-3s, such as linseed, flaxseed, and fish oil, not only avoid aggravating inflammation but can actively help reduce it (see Table 2).

How Much Oil Should You Feed?

The ideal amount of oil in a horse’s diet depends on several factors, including workload, body condition, and how much grain you intend to replace. Horses can safely tolerate up to 20% of their total diet as oil, which typically equates to:

750–1000 ml of oil per day for a horse in moderate to heavy work.

However, because oils contain no protein, minerals, or vitamins, these nutrients must be carefully balanced, especially for young, growing horses and pregnant or lactating mares. One critical consideration is vitamin E, which should be supplemented at 1 mg (or International Unit, i.u.) per ml of added oil, equivalent to 200–250 i.u. per cup of oil, to support antioxidant protection and muscle health.

Key considerations when supplementing oil in a horse’s diet:

Gut adaptation: Allow up to 4 weeks for the digestive system to adjust to added oil.
Start slow: Begin with 50 ml per day, increasing gradually by 10–20 ml daily until the target amount is reached.
Muscle adaptation: Horses need 6 to 11 weeks for their muscles to adjust to using fat as a fuel source. Start supplementation well before any strenuous activity or competition.

Conclusion: A Simple Change with Big Benefits

Adding oil to your horse’s diet isn’t just about increasing energy; it’s a strategic way to support digestive health, enhance metabolic function, and promote overall well-being. Whether your horse is a weekend trail companion or a high-performance athlete, incorporating oil, especially omega-rich varieties, offers a safe and effective way to fuel their body and protect their gut.

Omega-3 oils play a vital role in balancing antioxidants, vitamins, and minerals that are essential for disease resistance and managing inflammation and allergic responses. However, their benefits are maximised only when paired with adequate levels of key nutrients like vitamin E, selenium, copper, and zinc. That’s where Jenquine all-4-feet® comes in, providing a comprehensive blend of protein, vitamins, minerals, antioxidants, and biotin to complement any diet, including those enriched with oil.

While the effectiveness of many so-called “ergogenic aids” in horses remains uncertain, the advantages of oils, especially omega-3s, are well-supported. For both horses and humans, ensuring a consistent daily intake of quality oils is a cornerstone of health and performance.

Better digestion. More energy. That’s the good oil.

References

Alberghina, D., Giannetto, C., Visser, E. K., & Ellis, A. D. (2010). Effect of diet on plasma tryptophan and serotonin in trained mares and geldings. Veterinary Record, 166(5), 133–136.

Holland, J., Kronfeld, D., Hoffman, R., Greiwe-Crandell, K., Boyd, T., Cooper, W., et al. (1996). Weaning stress is affected by nutrition and weaning methods. Pferdeheilkunde, 12, 257–260.

Hothersall, B., & Nicol, C. (2009). Role of diet and feeding in normal and stereotypic behaviors in horses. Veterinary Clinics of North America: Equine Practice, 25(1), 167–181.

Kim, S., Choi, Y., Kim, J., Wickens, C. L., & Yoon, M. (Year not provided). Soybean oil supplement induces increased approaching behavior to humans and alters serotonin concentrations in horses. Journal name not provided.

Nicol, C. J., Badnell-Waters, A. J., Bice, R., Kelland, A., Wilson, A. D., & Harris, P. A. (2005). The effects of diet and weaning method on the behaviour of young horses. Applied Animal Behaviour Science, 95(3–4), 205–221.

Luthersson, N., Nielsen, K. H., Harris, P., & Parkin, T. D. H. (2009). Risk factors associated with equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark. Equine Veterinary Journal, 41(7), 625–630.

Redondo, J., Carranza, J., & Trigo, P. (2009). Fat diet reduces stress and intensity of startle reaction in horses. Applied Animal Behaviour Science, 118(1–2), 69–75.

Dr Jennifer Stewart
BVSc BSc PhD Equine Veterinarian and Consultant Nutritionist

The Case for Oil in Equine Nutrition