Feeding Fat to Horses: Benefits, Best Sources and How Much Is Safe

By Dr Duncan Houston

Fat can be one of the most useful tools in equine nutrition when a horse needs more calories without a larger grain meal.

It is particularly valuable for hard keepers, selected performance horses, some seniors and underweight horses that need a lower-starch ration. However, pouring oil over an existing diet is not automatically healthier. Too much fat can create obesity, displace essential nutrients, reduce fibre digestion and leave the whole ration unbalanced.

The goal is not simply to make the diet higher in fat.

It is to provide the horse with the calories they genuinely need while preserving forage intake, digestive health, body condition and overall nutritional balance.

Quick Answer

Fat provides approximately 2.25 times more energy by weight than carbohydrate, making it an efficient way to increase calories without feeding larger grain meals.

Most horses can digest added fat well when it is introduced gradually over three to four weeks. However, fat does not prevent gastric ulcers, cure inflammation or replace forage, protein, vitamins and minerals. The right amount depends on the horse’s weight, body condition, workload, health and the rest of the ration. (ceh.vetmed.ucdavis.edu)

Why Feed Fat to a Horse?

Dietary fat is primarily used to increase the energy density of the ration.

It may be considered when a horse:

• Struggles to maintain body condition

• Cannot safely consume larger grain meals

• Is in sustained or demanding work

• Needs a lower-starch calorie source

• Has reduced appetite or limited meal capacity

• Is a senior requiring a more digestible complete feed

• Has a veterinarian-diagnosed muscle disorder requiring dietary modification

• Is lactating or has another legitimate increase in energy demand

Fat provides substantially more energy per kilogram than starch, sugar or protein. It also produces a smaller post-meal glucose and insulin response than cereal grain, which can make it useful when calories are needed but large starch meals are inappropriate. (ceh.vetmed.ucdavis.edu)

However, many horses maintain healthy body condition on forage alone and do not require added fat or concentrate. Fat should be added because the ration has an identified energy deficit, not because a shiny coat sounds appealing. (Merck Veterinary Manual)

Fat Is Concentrated Energy, Not Complete Nutrition

Pure oil supplies calories and fatty acids.

It does not provide meaningful amounts of:

• Fibre

• Protein

• Lysine or other essential amino acids

• Calcium

• Phosphorus

• Copper

• Zinc

• Selenium

• Most vitamins

This becomes important when oil is added while the quantity of a fortified commercial feed is reduced. The horse may receive enough calories but no longer receive the feed’s intended amount of protein, vitamins and minerals.

A horse can therefore gain weight while the ration quietly becomes nutritionally worse.

Commercial high-fat feeds are often easier to balance because they combine energy with protein, minerals and vitamins. That advantage applies only when the product is fed at or near its recommended rate. Feeding a small handful of a fortified feed designed to be given in kilograms may not deliver the nutrients promised on the label. (AAEP)

How Do Horses Use Dietary Fat?

Fat is digested and absorbed mainly in the small intestine. Once absorbed, fatty acids can be stored in body tissue or used to produce energy.

Fat is most useful during aerobic metabolism, when oxygen is available to the muscles. This makes it particularly relevant during:

• Endurance riding

• Long-distance work

• Sustained trotting or cantering

• Lower-intensity conditioning

• Long training sessions

Fat cannot supply energy as rapidly as carbohydrate during explosive, high-intensity activity. Sprinting, racing, repeated jumping efforts and other anaerobic work still depend heavily on glucose and muscle glycogen. (PubMed)

This is why the most accurate description is not “fat replaces carbohydrates.”

It is:

Fat can replace part of the energy previously provided by starch, while sufficient carbohydrate remains available for high-intensity work and recovery.

Does Feeding Fat Improve Stamina?

It may help selected horses, but the effect should not be oversold.

Once a horse has adapted to a high-fat ration, muscle may use more fatty acids during lower-intensity exercise. This can spare some glucose and glycogen, potentially delaying fatigue during prolonged aerobic work. (Merck Veterinary Manual)

However:

• Not every study shows a measurable performance improvement.

• Fat does not compensate for poor fitness.

• It does not correct dehydration or electrolyte loss.

• It cannot replace carbohydrates needed for high-intensity work.

• High-fat feeding may slow muscle glycogen replenishment after exercise.

• The horse needs several weeks of adaptation before performance effects can be assessed.

A high-fat ration may be useful for an endurance horse or hard-working horse that needs more calories. It is not a legal nutritional turbo button.

How Long Does Fat Adaptation Take?

Horses should generally be given approximately three to four weeks to adapt fully to a higher-fat ration.

During this period, the digestive system, liver, muscles and metabolic pathways adjust to the increased fat supply. Introducing a large quantity abruptly can reduce palatability, alter manure consistency and potentially interfere with normal fibre digestion. (Merck Veterinary Manual)

For a horse beginning an oil supplement, a conservative example would be:

1. Begin with a small measured amount.

2. Maintain that quantity for several days.

3. Increase in small steps every three to four days.

4. Divide larger quantities between at least two meals.

5. Stop increasing if the horse leaves feed, develops loose manure or appears uncomfortable.

6. Allow the full three to four weeks before judging the final response.

Do not free-pour oil into the bucket. Measure it.

The difference between “a splash” and 300 millilitres becomes remarkably creative when several people feed the same horse.

How Much Oil Can a Horse Safely Eat?

There is no universal dose for every horse.

Current Merck guidance states that horses can tolerate a total ration containing approximately 10% fat when introduced gradually. It lists an upper limit for soybean oil of approximately 0.7 grams per kilogram of body weight per day and illustrates this as roughly 500 millilitres, or two cups, for a 500-kilogram horse. Penn State similarly advises that supplemental oil should generally not exceed one to two cups or approximately 20% of the horse’s dietary energy. (Merck Veterinary Manual)

That is an upper limit, not a recommended target.

Many horses need considerably less. The correct amount depends on:

• Body weight

• Current body-condition score

• Target body condition

• Existing fat in the ration

• Forage quality

• Workload

• Metabolic health

• Whether grain is being removed

• Which oil or feed is used

• Total digestible energy requirement

A pony should not receive the same volume as a 600-kilogram sport horse merely because both own buckets.

A Practical Way to Introduce Oil

For an average adult horse, a veterinarian or equine nutritionist may create a plan that starts with roughly 30 to 60 millilitres daily and increases gradually towards the calculated target.

Larger final quantities should be divided between meals and introduced over several weeks. A horse receiving 250 to 500 millilitres daily needs a properly balanced ration rather than a casual top-up.

Monitor:

• Appetite

• Amount of feed left behind

• Manure consistency

• Body weight

• Body-condition score

• Girth measurement

• Coat condition

• Energy and behaviour

• Exercise recovery

Record body weight or weight-tape measurements every one to two weeks. Healthy weight gain should be gradual. Merck suggests that an uncomplicated horse needing condition may take approximately 30 to 90 days to gain around 23 kilograms, although individual responses vary considerably. (Merck Veterinary Manual)

Which Horses May Benefit From Added Fat?

Hard Keepers

A healthy horse that cannot maintain weight despite adequate forage may benefit from additional fat.

Before adding calories, investigate why the horse is thin.

Possible causes include:

• Insufficient forage

• Poor-quality forage

• Dental disease

• Parasites

• Gastric disease

• Chronic pain

• Social competition

• Heavy workload

• PPID

• Liver or kidney disease

• Chronic infection

• Malabsorption

• Cancer

• Inadequate protein or amino acids

The mistake I see most often is treating “thin” as the diagnosis.

Oil may add weight while the fractured tooth, gastric disease or chronic illness remains exactly where it was. Merck specifically recommends identifying underlying health, dental and management problems before simply increasing calories. (Merck Veterinary Manual)

Performance Horses

Performance horses may need more energy than they can comfortably obtain from forage alone.

Replacing part of a large grain ration with fat can:

• Increase caloric density

• Reduce the total size of concentrate meals

• Lower dietary starch

• Support sustained aerobic work

• Help maintain condition during training

However, healthy horses performing intense work still need adequate carbohydrate availability. Eliminating starch and sugar indiscriminately can impair glycogen recovery and performance. (Merck Veterinary Manual)

The best performance ration balances:

• Forage

• Digestible fibre

• Fat

• Appropriate starch

• Protein and amino acids

• Electrolytes

• Vitamins and minerals

The athlete needs a complete fuel system, not one fashionable macronutrient.

Senior Horses

Some older horses benefit from high-fat complete feeds because these products can deliver concentrated energy in an easily chewed form.

The horse still needs assessment for:

• Missing or painful teeth

• Quidding

• PPID

• Liver or kidney disease

• Chronic diarrhoea

• Malabsorption

• Arthritis limiting access to feed

• Competition from younger horses

A high-fat senior feed can be useful when it replaces forage that the horse can no longer chew effectively. Straight oil alone does not provide the fibre, protein or mineral support that a senior horse may require. (ceh.vetmed.ucdavis.edu)

Underweight Horses With Insulin Dysregulation

An underweight horse with insulin dysregulation may need additional calories while still requiring a low-sugar, low-starch ration.

In this specific situation, oil or a properly selected low-NSC, high-fat feed can help increase energy without provoking the same insulin response as a cereal-heavy meal. Merck identifies oil as one potential calorie source for underweight metabolic horses. (Merck Veterinary Manual)

This does not mean every horse with equine metabolic syndrome should receive fat.

Most insulin-dysregulated horses are overweight or easy keepers. Adding oil to an already excessive energy intake can increase obesity, worsen insulin dysregulation and maintain laminitis risk. (ceh.vetmed.ucdavis.edu)

The distinction is critical:

• Underweight metabolic horse: may need low-NSC additional calories.

• Overweight metabolic horse: usually needs controlled calories, not added oil.

Horses With Certain Muscle Disorders

A high-fat, low-starch ration is used in some horses with polysaccharide storage myopathy and recurrent exertional rhabdomyolysis.

The exact plan depends on:

• The diagnosis

• Whether the horse needs extra calories

• Exercise programme

• Body condition

• Muscle enzyme results

• Type of myopathy

• Individual response

For PSSM, dietary management commonly focuses on reducing starch and providing a proportion of digestible energy from fat alongside consistent daily exercise. Horses with recurrent exertional rhabdomyolysis may also benefit from lower-starch, higher-fat feeds, particularly when their energy requirements are high. (Merck Veterinary Manual)

Not every horse labelled with “PSSM2” or myofibrillar myopathy requires a very high-fat diet. Current guidance for myofibrillar myopathy can include moderate starch and moderate fat rather than the traditional PSSM ration. (Merck Veterinary Manual)

A muscle-disease diet should follow a confirmed diagnosis, not a social-media acronym.

Lactating Mares and Horses With High Energy Demands

Lactating mares and horses in very heavy work may struggle to consume enough feed volume to meet energy needs.

A balanced high-fat commercial feed can help increase calories without excessively increasing meal size. Plain oil is less useful when the horse also needs more high-quality protein, lysine, calcium, phosphorus, copper and zinc.

In these cases, the complete nutrient package matters more than the oil bottle.

Which Horses Should Not Be Given Extra Fat Without Veterinary Advice?

Overweight Horses and Easy Keepers

Fat is calorie-dense.

It is the wrong supplement for a horse that already has:

• A body-condition score above ideal

• A cresty neck

• Regional fat deposits

• Insulin dysregulation

• Previous laminitis

• Minimal workload

• Unrestricted pasture access

A low-starch label does not make a feed low-calorie.

An overweight horse can become fatter on a low-starch, high-fat diet with impressive efficiency.

Horses With Liver Disease

The liver is central to fat metabolism.

Merck advises that fat should not be added to the diet of horses with hepatic disease. Horses with jaundice, abnormal liver enzymes, photosensitivity, unexplained neurological signs or diagnosed liver dysfunction need an individually formulated veterinary diet. (Merck Veterinary Manual)

Severely Starved Horses

Oil is not an appropriate first feed for a severely starved horse.

Refeeding syndrome can cause dangerous shifts in phosphorus, magnesium and other electrolytes. Research from UC Davis supports beginning rehabilitation with small, frequent quantities of good-quality alfalfa rather than using fat as an early calorie shortcut. (ceh.vetmed.ucdavis.edu)

A chronically starved horse requires veterinary supervision and a staged refeeding programme.

Horses With Active Diarrhoea or Feed Intolerance

Do not continue increasing fat if a horse develops:

• Loose or oily manure

• Diarrhoea

• Bloating

• Reduced appetite

• Feed refusal

• Abdominal discomfort

These signs do not necessarily mean fat is the sole cause, but the dietary change should be paused while the horse is assessed.

Horses Already Receiving a High-Fat Feed

Many performance, senior and conditioning feeds already contain 8% to 14% crude fat.

Adding several cups of oil on top may provide far more energy than expected and could push the whole ration beyond the intended fat concentration.

Always calculate the fat already supplied by:

• Commercial concentrate

• Rice bran

• Ground flaxseed

• Oilseed meals

• Supplements

• Added oil

The guaranteed analysis lists crude fat as a percentage, but the feed’s total energy value may need to be obtained from the manufacturer. (AAEP)

Does Fat Reduce the Risks of Feeding Grain?

Replacing part of a large grain ration with fat can reduce dietary starch and the risk associated with starch escaping small-intestinal digestion.

Large starch and sugar meals can lead to rapid fermentation in the hindgut, altered microbial populations and increased production of acid and other compounds associated with digestive upset, colic and laminitis.

Merck notes that diets in which high-starch or high-sugar concentrates account for more than half of ration dry matter have been associated with increased risk of colic, laminitis and equine gastric ulcer syndrome. No more than 0.5% of body weight in grain-based concentrate should be fed in one meal. (Merck Veterinary Manual)

For a 500-kilogram horse, that upper meal limit is approximately 2.5 kilograms of grain-based concentrate. Many horses should receive considerably less.

Replacing some grain with fat can therefore be sensible.

But “less grain” is not the same as “no risk.”

Fat does not prevent:

• Impaction colic

• Sand accumulation

• Large-colon displacement

• Enteroliths

• Parasite disease

• Choke

• Gastric rupture

• Intestinal strangulation

It improves one part of the ration. It does not negotiate immunity from every form of colic.

Does Feeding Fat Prevent Gastric Ulcers?

No.

Fat may allow owners to reduce high-starch concentrate meals, which can be useful in an ulcer-conscious feeding programme. However, dietary oil itself has not been proven to prevent gastric ulcers.

In a controlled study, dietary oils did not prevent ulcers from developing in the nonglandular portion of the equine stomach. (PubMed)

The most important nutritional measures for reducing squamous gastric ulcer risk remain:

• Avoiding prolonged periods without forage

• Providing frequent forage access

• Reducing large starch meals

• Feeding alfalfa or lucerne where appropriate

• Avoiding intense exercise on an empty stomach

• Managing travel and training stress

• Diagnosing and treating ulcers properly

Frequent forage intake and the calcium and protein in alfalfa can help buffer gastric acid. (Merck Veterinary Manual)

Oil can form part of an ulcer-friendly ration.

It is not ulcer medication.

Does Fat Prevent Colic?

Not directly.

A lower-starch ration may reduce some grain-associated digestive risks, but colic is a clinical sign with many possible causes.

A horse with a history of colic needs the cause reviewed before the diet is changed. Depending on the diagnosis, the priority may instead be:

• More water

• Better dental care

• More digestible forage

• Reduced sand exposure

• Parasite control

• Increased movement

• Smaller meals

• Different forage

• Treatment of gastric disease

• Surgery

“Colic-prone” is not a nutritional diagnosis.

Does Fat Make Horses Calmer?

Some owners report that horses appear less excitable after calories from cereal grain are replaced with fat and fibre.

This may relate to lower post-meal glucose and insulin fluctuations or simply to reducing large high-starch meals. Some equine studies have reported changes in behavioural reactivity on higher-fat, lower-starch rations, but the response is not universal. (ceh.vetmed.ucdavis.edu)

Fat is not a sedative.

A fresh, under-exercised or painful horse will not become a quiet schoolmaster because someone added canola oil.

The Best Fat Sources for Horses

Vegetable Oil

Examples include:

• Canola oil

• Soybean oil

• Corn oil

• Flaxseed or linseed oil

• Camelina oil

Advantages:

• Highly concentrated calories

• Easy to measure

• Usually economical

• No added starch or sugar

• Useful when feed volume must remain low

Limitations:

• Provides no protein or minerals

• Can reduce palatability

• Can become rancid

• Requires gradual introduction

• Large quantities may interfere with fibre digestion

• Fatty-acid profiles differ substantially

For weight gain alone, calorie content is broadly similar between edible vegetable oils. The main differences concern fatty-acid profile, flavour, stability and price.

Stabilised Rice Bran

Rice bran provides fat, fibre and additional nutrients in a dry, palatable form.

However, rice bran is naturally high in phosphorus and low in calcium. Choose a stabilised, calcium-fortified equine product or ensure the full ration’s calcium-to-phosphorus balance is correct. (Merck Veterinary Manual)

Rice bran is also not automatically low in starch or sugar. Merck advises caution when feeding it to insulin-dysregulated horses. (Merck Veterinary Manual)

Ground Flaxseed or Linseed

Flaxseed supplies:

• Fat

• Alpha-linolenic acid

• Fibre

• Some protein

It is less calorie-dense by volume than pure oil but can be easier to handle and more palatable.

Use a product that is appropriately processed and stored. Ground seeds and their oils are vulnerable to oxidation once exposed to air.

Chia Seed

Chia supplies alpha-linolenic acid, fibre and protein.

It can contribute useful nutrients, but the marketing often runs several furlongs ahead of the evidence. It should still be calculated as part of the complete ration rather than added in unlimited scoops.

Commercial High-Fat Feed

A properly formulated high-fat feed may be the best option when the horse needs both calories and nutritional fortification.

Check:

• Digestible energy

• Crude fat

• Starch and sugar

• Fibre

• Protein and lysine

• Calcium and phosphorus

• Vitamin E

• Recommended feeding rate

• Whether it is a complete feed or concentrate

A product containing 10% fat is not necessarily lower in starch than one containing 6% fat. Ask the manufacturer for the actual starch, sugar and energy values when these are not stated on the label.

Fish Oil or Algal Oil

Marine oils provide the long-chain omega-3 fatty acids EPA and DHA directly.

They may be useful when the goal is modifying fatty-acid intake rather than simply adding calories. Limitations include:

• Cost

• Palatability

• Odour

• Oxidation

• Variable EPA and DHA concentration

• Need for careful storage

Fish and algal oils are generally used in smaller quantities as fatty-acid supplements rather than as the main source of weight-gain calories.

Omega-3 and Omega-6: The Important Correction

Omega-3 is not simply “good,” and omega-6 is not simply “bad.”

Both fatty-acid families participate in normal cell function, skin health, reproduction, immunity and inflammatory signalling.

The relevant question is:

Which fatty acids is the horse receiving, in what quantity, and for what clinical purpose?

There is currently no clear evidence-based recommendation for an ideal omega-6-to-omega-3 ratio in equine diets. (PMC)

Plant Omega-3 Sources

Flaxseed, chia, camelina and some other plant oils primarily provide alpha-linolenic acid, or ALA.

Horses can convert some ALA into EPA, but available equine research suggests that ALA supplementation does not reliably increase DHA to the same degree as directly feeding a marine source. (PMC)

Marine Omega-3 Sources

Fish and algal oils provide EPA and DHA directly.

Studies have shown that marine oil supplementation can increase circulating EPA and DHA more effectively than plant ALA alone. (PMC)

That does not mean every horse needs fish oil.

Evidence for benefits involving joints, respiratory disease, skin, reproduction and exercise recovery is developing, but product claims are often broader than the clinical research. Recent studies show that different oils can alter plasma or skin fatty-acid profiles and some inflammatory responses, but these findings should not be interpreted as proof that an oil treats arthritis, asthma or another medical condition. (PubMed)

Does Corn Oil Cause Inflammation?

Corn oil is rich in omega-6 linoleic acid.

That does not mean it directly causes inflammatory disease in every horse. Omega-6 fatty acids are essential and participate in normal immune and healing processes.

For a horse requiring additional calories, corn oil can still supply energy effectively. However, where the overall ration already contains substantial cereal grain and other omega-6-rich ingredients, a source containing more ALA or direct EPA and DHA may better fit the desired fatty-acid profile.

Do not diagnose “systemic inflammation” by looking at one ingredient.

Review the entire ration and the actual horse.

Does Feeding Fat Help Joints, Skin or Hooves?

Increasing dietary fat can improve coat gloss in some horses, and different oil sources can change the fatty-acid composition of skin and blood.

That does not prove that the horse’s joints, hooves or immune system have been clinically improved.

A shiny coat may show that the horse is receiving more oil.

It does not rule out:

• Poor mineral balance

• Dental disease

• Gastric ulcers

• Insulin dysregulation

• Arthritis

• Hoof disease

• Vitamin deficiency

Research into omega-3 supplementation is promising in selected areas, but oil should be treated as nutrition rather than as a replacement for veterinary diagnosis or medication. (PubMed)

Vitamin E and High-Fat Diets

Vitamin E is the main vitamin that needs particular attention when dietary fat is increased.

Fat metabolism and oxidation can increase the horse’s antioxidant requirements. Horses in prolonged aerobic work, horses without fresh pasture and horses receiving diets containing more than approximately 5% fat may require additional vitamin E. Current Merck guidance suggests that an additional 500 to 1,000 IU daily may be needed in some of these horses, depending on the total ration and workload. (Merck Veterinary Manual)

The correct amount depends on:

• Total vitamin E already in the feed

• Access to fresh pasture

• Natural versus synthetic vitamin E

• Workload

• Muscle disease

• Fat intake

• Selenium intake

• Medical history

Do not automatically add large quantities of vitamins A, D and K because oil has been added.

Fat-soluble vitamins can accumulate, and excessive vitamin A or D can be toxic. The ration should be calculated, not decorated with extra tubs.

Rancidity and Storage

Unsaturated fats can oxidise and become rancid, particularly when exposed to:

• Heat

• Light

• Oxygen

• Moisture

• Prolonged storage

Rancid oil may smell stale, paint-like, fishy or unusually bitter. Horses may refuse it, and oxidised fat increases the dietary oxidative burden. UC Davis advises keeping high-fat feed fresh and avoiding products stored for prolonged periods in hot environments. (ceh.vetmed.ucdavis.edu)

Store oil:

• In a sealed container

• In a cool, dark location

• Away from direct sunlight

• In quantities that will be used promptly

• According to the manufacturer’s instructions

Flaxseed, fish and other highly unsaturated oils require particularly careful storage.

Do not attempt to disguise rancid oil with molasses or flavouring. The horse is not being fussy. The horse may simply have a more functional nose than the person holding the bucket.

Can Too Much Fat Reduce Fibre Digestion?

Yes.

At very high intakes, supplemental oil may interfere with fibre digestion in the hindgut. Merck cites reduced fibre digestibility in horses fed soybean oil at one gram per kilogram of body weight daily and therefore advises a lower upper limit. (Merck Veterinary Manual)

This is another reason to avoid assuming that more oil means faster weight gain.

The horse’s digestive system is fundamentally built around forage fermentation. Fat should support that system rather than displace or interfere with it.

Forage Must Remain the Foundation

Most horses should receive at least half of their total ration as forage, and many should receive considerably more.

Good-quality pasture, hay and appropriate forage alternatives provide:

• Fibre

• Chewing time

• Saliva

• Hindgut fermentation

• Volatile fatty acids

• Normal gastrointestinal motility

• Behavioural enrichment

Merck recommends a general total intake of approximately 2% to 2.5% of body weight in dry matter for an average healthy horse, with at least 50% coming from forage. Exact needs vary with body condition, workload, forage quality and health. (Merck Veterinary Manual)

Oil should not be used to justify reducing forage below a safe level.

The bucket may supply calories. It does not replace grazing behaviour or a functioning hindgut.

How Worried Should You Be?

Lower Risk

The horse:

• Is healthy but slightly underweight

• Has had dental and medical causes investigated

• Receives adequate forage

• Has normal manure

• Has good appetite

• Is being introduced gradually to a measured amount

• Has the full ration properly balanced

What to do: continue gradual introduction and monitor weight and body condition every one to two weeks.

Moderate Risk

The horse:

• Needs a large amount of oil to maintain weight

• Is leaving oily feed behind

• Has mildly loose manure

• Has not had a recent dental examination

• Is receiving less commercial feed than the label recommends

• Is not gaining after several weeks

• Has no forage analysis or calculated ration

What to do: stop increasing the oil and arrange a ration review. Investigate why the energy requirement appears so high.

High Risk

The horse:

• Is obese or insulin dysregulated

• Has a history of laminitis

• Has diagnosed liver disease

• Has chronic diarrhoea

• Has unexplained weight loss

• Is severely starved

• Has poor appetite

• Is receiving several overlapping fat supplements

• Has developed recurrent abdominal discomfort after the diet change

What to do: do not continue altering the ration without veterinary or equine nutrition guidance.

Critical

The horse develops:

• Severe colic

• Repeated rolling

• Profuse watery diarrhoea

• Complete feed refusal

• Weakness or collapse

• Signs of laminitis

• Severe muscle stiffness or sweating

• Dark urine after exercise

• Jaundice

• Neurological abnormalities

What to do: stop feeding and seek urgent veterinary advice. These signs should not be managed by changing the oil quantity and waiting for morning.

When Is This an Emergency?

Call your veterinarian urgently if a horse develops:

• Persistent or severe abdominal pain

• Repeated lying down or rolling

• Marked abdominal distension

• No manure production

• Profuse diarrhoea

• Sudden refusal of all feed

• Fever or depression

• Hot painful feet or a bounding digital pulse

• Reluctance to move or a rocked-back stance

• Severe muscle stiffness after work

• Sweating with dark brown urine

• Yellow gums or eyes

• Weakness, tremors or collapse

Particular urgency applies when a pony, miniature horse, donkey or obese horse stops eating because these animals are at increased risk of hyperlipemia.

Do not assume that a recently changed diet explains every sign. A horse can develop a surgical colic on the same day someone starts flaxseed oil. The calendar is not a diagnosis.

What Should You Do Before Adding Fat?

1. Confirm That More Calories Are Needed

Assess:

• Body weight

• Body-condition score

• Topline

• Workload

• Forage intake

• Current ration

• Seasonal changes

• Whether the horse is actually losing weight

A lean fit event horse and an underweight horse are not necessarily the same thing.

2. Investigate Unexplained Weight Loss

Arrange a veterinary and dental assessment when weight loss is:

• New

• Progressive

• Significant

• Unexplained

• Accompanied by diarrhoea, poor appetite or reduced performance

3. Weigh the Forage and Feed

Do not estimate by flakes, scoops or bucket depth.

Forage density varies, and two scoops of different feeds can differ substantially in weight and calories.

4. Analyse the Forage

A forage analysis can reveal:

• Energy

• Protein

• Sugar and starch

• Calcium

• Phosphorus

• Other important minerals

Many ration problems are easier to solve once the largest part of the diet is no longer a mystery.

5. Decide What the Fat Is Replacing

Added fat may:

• Supplement forage calories

• Replace part of a grain ration

• Replace an unsuitable feed

• Increase energy without increasing meal size

Do not simply add oil on top of every existing calorie unless weight gain is genuinely required.

6. Choose the Appropriate Source

Select oil, rice bran, flaxseed or a commercial high-fat feed according to:

• Calorie target

• Metabolic status

• Fatty-acid goal

• Palatability

• Storage

• Mineral balance

• Feeding practicality

7. Introduce It Gradually

Allow three to four weeks for full adaptation.

8. Balance the Remaining Ration

Review:

• Protein

• Lysine

• Calcium and phosphorus

• Copper and zinc

• Selenium

• Salt

• Vitamin E

• Total starch and sugar

9. Monitor the Result

Reassess after two to four weeks.

The relevant result is not merely an empty bucket.

It is whether the horse:

• Gains appropriate condition

• Maintains normal manure

• Eats willingly

• Performs well

• Avoids becoming overweight

• Remains metabolically and nutritionally healthy

Common Mistakes Horse Owners Make

Adding Oil Without Reducing Anything Else

This may be appropriate for a thin horse, but in a horse already meeting its energy requirement it simply creates a calorie surplus.

Starting With a Full Cup

Large sudden changes reduce palatability and do not allow proper metabolic adaptation.

Assuming Low Starch Means Low Calorie

A high-fat feed may be extremely calorie-dense even when its starch content is low.

Using Oil Instead of Investigating Weight Loss

Oil cannot treat dental disease, PPID, cancer, chronic pain or malabsorption.

Treating Rice Bran as Automatically Low NSC

Rice bran can contain meaningful starch and is naturally high in phosphorus. Read the analysis and choose a calcium-balanced product. (Merck Veterinary Manual)

Assuming Fat Prevents Ulcers

It may help reduce cereal grain, but oil itself has not been shown to prevent gastric ulcer development. (PubMed)

Calling Omega-6 Poisonous

Omega-6 fatty acids are biologically necessary. The ideal omega ratio for horses has not yet been established.

Forgetting Vitamin E

A high-fat diet, particularly in a working horse without pasture, should trigger a review of total vitamin E intake.

Using Oil as the First Feed for a Starved Horse

Severely malnourished horses require a controlled veterinary refeeding protocol.

Judging the Diet by Coat Shine

A glossy horse can still have an unbalanced ration.

How to Feed Fat More Safely

• Keep forage as the foundation.

• Confirm that the horse needs more calories.

• Weigh all feeds.

• Measure oil in millilitres.

• Introduce it over three to four weeks.

• Divide larger amounts between meals.

• Maintain unrestricted clean water.

• Check the existing crude-fat content of commercial feeds.

• Review vitamin E.

• Store oils correctly.

• Do not use rancid products.

• Monitor manure and appetite.

• Reassess body condition regularly.

• Stop increasing the dose when the nutritional goal is achieved.

The safest amount is not the maximum quantity the horse will tolerate.

It is the minimum amount that helps the ration achieve its intended purpose.

Will Feeding Fat Help My Horse Gain Weight?

It can, provided the horse is consuming and absorbing the added calories.

The outlook is better when:

• The horse is otherwise healthy

• Dental function is adequate

• Forage intake is sufficient

• The ration is balanced

• Fat is introduced gradually

• The horse genuinely needs more energy

• The underlying workload is understood

The response may be poor when:

• The horse has untreated disease

• Feed is being lost to competition

• Forage quality is inadequate

• The horse dislikes oily feed

• Fat is displacing essential nutrients

• Malabsorption is present

• The horse is expending more energy than expected

• The calorie increase is too small to matter

Healthy weight gain is usually measured over weeks to months, not several days.

FAQs About Feeding Fat to Horses

What is the best oil to feed a horse?

There is no single best oil for every horse. Canola, soybean and corn oil can all provide concentrated calories. Flaxseed or camelina oil supplies more ALA, while fish or algal products provide direct EPA and DHA. The best choice depends on whether the goal is calories, fatty-acid modification, palatability or cost.

How much oil can I give my horse?

The correct amount depends on body weight and the rest of the ration. For a 500-kilogram horse, authoritative guidance places the upper range around one to two cups daily, but this is not an appropriate starting amount and many horses need far less. Introduce oil gradually over three to four weeks. (extension.psu.edu)

Does feeding oil cause diarrhoea?

It can contribute to loose or greasy manure when introduced too quickly or fed at an excessive amount. Reduce or stop the new supplement and seek veterinary advice if diarrhoea is persistent, profuse or accompanied by illness.

Is oil safe for a horse with gastric ulcers?

Oil can provide calories while allowing starch reduction, but it does not treat or prevent ulcers. Forage access, meal frequency, exercise management and veterinary ulcer treatment remain more important. (PubMed)

Can a horse with equine metabolic syndrome have oil?

An underweight insulin-dysregulated horse may benefit from carefully calculated oil as a low-NSC calorie source. Most horses with EMS are overweight and should not receive extra calories without veterinary or nutritional guidance. (Merck Veterinary Manual)

Final Thoughts

Fat is a powerful nutritional tool because it adds a large amount of energy without requiring a large starch-heavy meal.

Used correctly, it can help:

• Hard keepers maintain weight

• Performance horses meet energy demands

• Selected seniors consume enough calories

• Underweight metabolic horses receive lower-NSC energy

• Horses with certain muscle disorders follow an appropriate therapeutic ration

Used carelessly, it can create:

• Obesity

• Poor appetite

• Loose manure

• Reduced fibre digestion

• Nutritional deficiencies

• Rancid feed exposure

• A falsely reassuring shiny coat

The most important rule is simple:

Do not add fat until you know why the horse needs it and what the fat will replace.

Keep forage at the centre of the ration, introduce added fat gradually, balance the protein, minerals and vitamins, and monitor the horse rather than the oil bottle.

Fat can make a good diet more useful.

It cannot make a badly designed diet good.

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Need help deciding whether your horse needs more calories, less starch or a different fat source? ASK A VET™ can help you organise their body condition, workload, current ration and health history before you make a major feeding change.