The Hidden Risks of Seed Oils in Horse Feed

Horses evolved consuming a forage-based diet naturally low in fat, typically in the region of 2–4% on a dry matter basis. This diet was also naturally higher in omega-3 fatty acids due to the consumption of fresh pasture.

Modern feeding practices that introduce concentrated oils, particularly refined seed oils, represent a significant departure from this evolutionary baseline and should be considered carefully in the context of long-term health.

Not all oils are created equal, and understanding these differences can help horse owners make more informed feeding decisions.

Why does the horse feed industry use seed oils in horse feed?

Horse feed companies sometimes spray seed oils on horse feed to increase calorie density, improve coat condition, reduce dust and provide a source of energy, especially for horses with specific needs like weight gain or those requiring a lower starch diet.

While oil does not directly trigger insulin release in the same way as starch or sugar, excessive fat intake can increase overall calorie consumption and contribute to weight gain. In horses, excess body fat is a well-established risk factor for insulin dysregulation and laminitis, meaning that overuse of oil may indirectly contribute to metabolic issues [1][2].

What is a Horse Appropriate Level of Fat in the Diet?

1. Baseline (natural / forage diet)

• Horses evolved eating forage with very low fat content (2–4%) (inferred from typical forage composition and feeding studies)
• Experimental diets in horses often start around 3% fat dry matter as a baseline [3]
  (Geelen et al., 2001)

This reflects the species-typical intake. This baseline is important, as it highlights the relatively small role fat plays in the natural equine diet. Any increase above this level should be viewed as supplemental rather than foundational.

2. Moderate fat supplementation (common & safe)

• Diets in research commonly range 5–10% fat, with:
  • Increased fat metabolism capacity
  • No major negative metabolic effects
• Horses adapt to fat by increasing fat-burning enzymes and lipid metabolism [4]
  (Orme et al., 1997)

This is why oil is widely used in performance diets.

3. Upper limits tested in studies

• Horses tolerated up to 15% of the total diet as fat without harming fibre digestion [5]
  (Williams et al., 2017)
• Other trials used diets up to:
  • 10–11% fat safely(Jansen et al., 2001)
  • 17% fat in concentrate without harming digestibility

But very high fat was shown to reduce fibre digestibility and risk of undigested fat reaching the hindgut, which may alter hindgut fermentation and fibre digestion (Schwartz, 2015)

Tolerance does not necessarily equate to optimal health. At higher inclusion levels, fat can begin to interfere with normal digestive processes, particularly the fermentation of fibre in the hindgut.

What “species-appropriate” for horses really means

Their evolutionary baseline is 2-4% fat content. The practical optimal range is likely to be around 6%. Higher is tolerated, but for the healthiest, long-term outcomes, being respectful of evolutionary needs is the wisest and most prudent choice.

This important nuance is often misunderstood. Horses are hindgut fermenters, not fat-adapted carnivores. They can use fat well, but it is not their primary evolutionary fuel. Fibre fermentation, not oils in horse feed, should always be their core energy system.

There are now many modern, high-quality, high-fibre horse feeds without seed oils in them on the market, and they are a better option for horses, combined with healthy oil and fat sources in moderation.

We feel that timing a feed after work is a better and more effective way to fuel future safe energy without creating hot behaviour. This timed bucket feed, for performance horses, utilises body biology and can be combined with daily bucket feeds, which utilise safe oil sources at evolutionarily appropriate levels.

Replenishing Glycogen for Performance and Recovery

Feeding after exercise plays an important role in supporting recovery, muscle health and the rebuilding of energy reserves [8]. During work, muscle glycogen, the stored form of carbohydrate, is used as a key fuel source, and depletion of these stores is associated with fatigue.

There is a recognised period following exercise where muscle becomes more responsive to glucose uptake. Providing carbohydrates during this time helps support how effectively this energy is utilised within the body, directing nutrients towards muscle recovery and glycogen replenishment, rather than contributing to excess circulating energy.

While glycogen restoration in horses is relatively slow and occurs over time, appropriate feeding during this period supports the overall recovery process as part of a balanced diet.

A combination of fast-release carbohydrates, such as flaked oats, and slower-release fibre sources, such as soaked beet pulp, provides both readily available glucose and sustained energy supply. This dual approach supports recovery while maintaining alignment with the horse’s natural reliance on fibre fermentation.

Importantly, when feeding is aligned with workload and overall energy requirements, carbohydrate intake does not inherently lead to excitability. Behavioural responses are more closely linked to total diet, feeding levels and individual sensitivity than to timing alone.

Adding essential amino acids to this post-exercise feed provides the key building blocks required for muscle repair and protein synthesis. These nutrients support the rebuilding of muscle tissue following exercise and contribute to long-term strength, topline development and resilience.

Why This Is Better Than High Oil Feeding

This approach is more effective and physiologically appropriate than relying on high oil diets. Oil does not contribute to glycogen restoration, and therefore does not support recovery in the same way. Feeding strategies that prioritise fibre and targeted carbohydrate intake are more closely aligned with the horse’s natural biology and energy systems.

Using a post-exercise feeding strategy that combines carbohydrates, fibre and essential amino acids can help to:

• Support the gradual restoration of glycogen stores
• Promote muscle repair and adaptation
• Maintain controlled energy levels without excessive starch
• Build sustainable energy reserves for future work

This targeted approach can make a meaningful difference to performance, recovery and long-term health.

The Problem with Seed Oils: Production Methods, GMOs, and Omega-6 Content

Seed oils, such as rapeseed oil, vegetable oil, and soybean oil, are commonly used in horse feeds and supplements. However, the production methods of these oils raise significant concerns.

Most seed oils are extracted using high heat and chemical solvents, which can degrade the oil’s natural structure and lead to the formation of oxidation products [9]. Additionally, the refining process often strips away beneficial nutrients, leaving behind a product that is far from natural.

Production Process of Common Seed Oils

GMO soy is engineered to be resistant to herbicides, which means it is often heavily sprayed with chemicals like glyphosate [12][13].

While regulatory bodies assess these residues as safe within defined limits [12], it is important to recognise that there is currently limited equine-specific research examining the long-term effects of chronic dietary exposure to pesticide residues.

In the absence of horse-specific data, existing regulatory frameworks for pesticide residues in food and feed are sometimes used as a proxy benchmark, providing context rather than definitive evidence of safety or harm [14].

This is particularly relevant when considering feed materials derived from intensively managed arable systems, where pesticide use is more extensive than in forage-based systems such as grass and hay [14].

As a result, some owners may choose to take a precautionary approach and minimise exposure where possible, particularly when considering cumulative or long-term dietary intake.

The Inflammatory Impact of Omega-6 Fatty Acids

Inflammation is a natural response to injury or infection, but chronic inflammation can contribute to a range of health challenges, including joint issues and metabolic disorders.

Omega-6 and omega-3 fatty acids play important but differing roles in inflammatory processes [11]. Fresh pasture, the natural diet of the horse, is naturally higher in omega-3 fatty acids and provides a more balanced fatty acid profile. Some equine nutritionists, including Eleanor Kellon, have noted that fresh grass can contain omega-3 to omega-6 ratios in the region of 4:1 or higher, reflecting the horse’s natural dietary baseline.

However, when grass is conserved as hay, omega-3 levels decrease due to oxidation and drying, already shifting the balance towards omega-6.

The addition of seed oils, which are typically high in omega-6 fatty acids, can further influence this balance. Depending on the types and amounts used, this may shift the overall dietary ratio substantially, in some cases towards levels more commonly discussed in human nutrition, such as 10:1 or higher, particularly where omega-3 intake is not actively supported.

Much of the research exploring omega-6 and omega-3 balance has been conducted in human nutrition. In these studies, lower ratios of omega-6 to omega-3, often in the region of 4:1 or below, are associated with more favourable health outcomes, while modern diets may exceed 10:1 or higher [10].

While equine-specific research in this area is more limited, the fundamental biological roles of these fatty acids are consistent across mammalian systems, and these findings are often used to help inform practical feeding approaches in horses.

Importantly, neither the National Research Council nor leading equine nutritionists such as Eleanor Kellon define a strict “ideal” omega-6 to omega-3 ratio for horses. Instead, the emphasis is placed on supporting a balanced intake that reflects the horse’s natural forage-based diet, rather than relying on fixed numerical targets.

A horse’s natural diet, based on fresh forage, tends to provide a more favourable omega-3 profile. However, when this is replaced with conserved forage and modern feed inputs, including seed oils, the balance can shift further toward omega-6.

From an equine physiology perspective, the key consideration is not simply whether oils can be fed, but whether their inclusion aligns with the horse’s natural dietary design. Horses evolved consuming low-fat, fibre-rich diets with a naturally balanced fatty acid profile.

While they can adapt to higher fat intakes, excessive reliance on processed seed oils introduces a combination of factors, including higher omega-6 intake, reduced reliance on fibre, and increased calorie density, that move the diet further away from this biological model. Over time, this may contribute to imbalances in metabolic health, digestive function and inflammatory status.

The Case for Healthier Oils: Cold-Pressed Linseed Oil and Micronised Linseed

To counteract the negative effects of seed oils, horse owners should consider healthier alternatives like micronised linseed or cold-pressed linseed oil.

Linseed oil, derived from flaxseeds, is rich in omega-3 fatty acids, which help to balance the omega-6 to omega-3 ratio and reduce inflammation.

Cold-pressed linseed oil is extracted without heat or chemicals, preserving its nutritional integrity and ensuring that horses receive the full benefits of the oil.

Micronised linseed, on the other hand, offers the whole goodness of the flaxseed in a highly digestible form. The micronisation process involves heating the seeds with infrared heat just enough to break down the cell walls, making the nutrients more bioavailable.

This method retains the natural balance of omega-3s, fibre, and essential nutrients. This makes micronised linseed a superior and cleaner choice to ensure adequate omega-3 levels when fed at a feed rate of 42 grams per 220 kg of bodyweight. To maintain optimal health, it’s essential to scrutinise the oils in horse feed included in your horse’s diet.

Micronised linseed is also effective when providing horses with extra calories for weight maintenance or gain and boosting protein where needed, as matched to a hay or haylage analysis.

Fed as a small amount over winter, or to horses who are short of omega-3 due to not eating spring or summer grass, it is essential to make sure omega-3 levels do not become depleted.

Nutritional Comparison of Common Oils and Linseed for Horses (Typical Values)

Feed Source	Omega-3 (%)	Omega-6 (%)	Protein (%)	Fibre (%)	Key Nutritional Characteristics
Rapeseed Oil (Refined)	8–11	18–25	0	0	Moderate omega balance, energy only
Rapeseed Oil (Cold-Pressed)	8–11	18–25	0	0	Similar profile, slightly less processed
Soybean Oil	6–8	50–55	0	0	High omega-6, low omega-3
Sunflower Oil	<1	60–70	0	0	Very high omega-6, negligible omega-3
Vegetable Oil Blends	Variable	Variable	0	0	Depends on source oils
Linseed Oil (Refined)	50–60	12–18	0	0	Very high omega-3, supports fatty acid balance
Linseed Oil (Cold-Pressed)	50–60	12–18	0	0	High omega-3 with minimal processing
Micronised Linseed	20–25	5–7	20–25	8–10	Omega-3 rich whole feed with fibre and protein

Copra Meal for Horses: MCT-Rich Oil Energy

Copra meal (derived from coconut) offers a unique addition to equine diets because it combines moderate-quality protein with a relatively high fat content, typically around 8–12% in copra meal, and higher in expeller or “coolstance”-type products (often 15–20% fat).

The fat contained within Copra is rich in medium-chain fatty acids (MCTs), particularly lauric and myristic acid, which are rapidly metabolised and can provide a readily available energy source without relying heavily on glucose metabolism.

We recommend copra meal as an additional feed ingredient, in a targeted bucket feed, which can contribute additional phosphorus, energy and protein. Copra’s amino acid profile is not as strong as traditional protein sources, and it does require careful balancing, but it can be a useful choice when combined with other feeds.

In practical terms, this makes copra useful as a low-starch, oil-rich feed that can complement other protein sources, helping to vary protein inputs and potentially broaden amino acid and mineral availability in the diet. Specific situations when it might be useful (up to 500 grams for a 500 kg horse) would be when devising a feed strategy for old horses, young horses and breeding mares. It also has a great place, along with high fibre feeds and oats in the diet of a horse in moderate to heavy work.

However, due to limited equine-specific research and its relatively low lysine content, it is always best used as part of a balanced feed approach where forage analysis informs the best feeds to add to a hay, haylage and grass-based diet.