What’s the Best Weight Gain Supplement for Horses?

Helping a horse gain weight is not always as straightforward as adding more grain to the diet. While grain can increase calorie intake, it is not always the safest or most effective way to add condition, especially for horses with digestive concerns or those that become reactive on high-starch feeds. ^[1]

Some horses lose condition because they are not getting enough digestible calories from forage. Others may be eating well but still struggle to maintain weight because of dental problems, digestive issues, stress, or inadequate protein and amino acid intake.

A better approach used by equine nutritionists is to first identify what is limiting healthy weight gain. Some horses benefit from feeding more fat, some need improved digestive support, and others need better protein quality to support topline and muscle development.

For many horses needing additional calories, Mad Barn’s w-3 Oil is the best overall weight gain supplement because it provides calorie-dense fat, omega-3 fatty acids, and natural vitamin E to support body condition without relying on high-starch feeds or excessive grain intake.

Some horses may also require targeted support for digestion, nutrient absorption, or muscle development. Horses that are eating enough but still struggle to maintain condition may benefit from Optimum Digestive Health, while horses lacking topline or muscle development may benefit from Three Amigos to support protein synthesis and lean muscle growth.

Does My Horse Need a Weight Gain Supplement?

Maintaining healthy body condition supports your horse’s physical appearance, energy reserves, muscle mass, performance, immune function, and overall health.

When a horse struggles to gain or maintain weight, owners may try feeding more grain, switching to a sweet feed, adding oil, or using a weight gain supplement. ^[1]

A horse may benefit from a weight gain supplement when its current forage and feeding program are not providing enough digestible energy to gain or maintain healthy body condition.

Horses can lose weight or condition for many different reasons. In some horses, weight loss reflects inadequate calorie intake relative to workload, weather, growth, lactation, or other metabolic demands.

Low calorie supply can arise from low forage quality, limited feed intake, or digestive inefficiency. In other horses, dental problems, stress, illness, inadequate protein quality, or imbalances in the overall diet can impact body condition.

The most effective approach is to identify what is limiting healthy weight gain in the horse’s current feeding and management program. In cases where there is no underlying health concern, weight gain starts with a balanced, forage-based diet that provides adequate calories, high-quality protein, vitamins, minerals, and water to support normal digestive function and nutrient utilization. ^[2]

Best Weight Gain Supplements for Horses

For horses that primarily need more calories, a fat-based weight gain supplement is often a better choice than simply increasing grain. Fat is a source of cool energy, helping increase calorie intake without adding bulk to the diet or relying on high-starch feeds. ^[3]

Fat provides 2.5x more calories per gram than grain and is highly digestible for most horses when introduced gradually. This can be especially useful for hard keepers, senior horses, performance horses, or horses that need additional calories but do not tolerate large concentrate meals well.

Mad Barn’s w-3 Oil is the best overall weight gain supplement for horses because it provides calorie-dense fat, omega-3 fatty acids, and natural vitamin E to support body condition. w-3 Oil is palatable, cost-effective, and easy to incorporate into almost any feeding program.

Additional Nutrition Support

Some horses need more than a high-calorie supplement to gain weight. If a horse is eating enough but still struggles to maintain condition, the issue may be related to how well the diet is balanced, digested, and utilized.

In these cases, the priority is to look beyond calories alone and evaluate the full feeding program, including:

• Forage intake and quality
• Total calorie intake relative to workload, age, and environment
• Protein quality and amino acid supply
• Vitamin and mineral balance
• Digestive function and feed utilization
• Water, salt, and overall feeding management

A horse with poor feed utilization may benefit from digestive support to help maintain hindgut function and improve nutrient use. A horse with poor topline or muscle development may need better protein quality or targeted amino acid supplementation rather than more calories alone.

This is why a diet evaluation is one of the most useful first steps when addressing poor body condition. It can help identify whether the horse primarily needs additional calories, improved forage quality, digestive support, targeted amino acids, or a more balanced overall diet.

Although supplements can help in many situations, they should complement a complete feeding program rather than simply adding more grain or calories on top of unresolved nutritional gaps.

It is also important to work with your veterinarian if your horse is losing weight unexpectedly, continues to lose condition despite adequate feed intake, or shows signs of illness, poor digestion, pain, reduced appetite, or declining performance.

Weight Gain Case Studies

Mad Barn nutritionists have worked with thousands of horses to address nutritional deficiencies and imbalances that can affect body condition, weight gain, muscle development, topline, exercise performance, and overall health.

The case studies below show how horses responded to dietary changes designed to support healthy weight gain and improved condition. To find out the best way to help your horse gain weight, submit their information for a free diet evaluation with one of our equine nutritionists.

Causes of Weight Loss & Poor Condition in Horses

Weight loss and poor condition can develop for many reasons, including inadequate energy intake, higher calorie demands, poor forage quality, digestive issues, dental disease, parasite burdens, and other underlying health problems.

Horses with increased energy requirements may struggle to maintain weight during heavy work, growth, lactation, aging, or cold weather exposure.

Temperament, breed type, and breeding status can also affect calorie needs. Hot-blooded horses, such as Thoroughbreds and Arabians, are often considered less thrifty than easy-keeping breeds and may require more calories to maintain the same body condition. Horses that are naturally active, anxious, reactive, or constantly moving in turnout may also expend more energy even when they are not in heavy work.

If the diet does not provide enough digestible energy to meet these demands, the horse may gradually lose condition over time. ^[1][2][3]

Forage quality and feeding management also play important roles. Horses consuming mature, low-quality hay or inconsistent forage meals may not consume enough digestible calories to support healthy weight maintenance. Social competition, stress, and long periods without forage can further reduce feed intake and feed efficiency. ^[4]

Health and digestive factors can also reduce how much energy and nutrition a horse actually absorbs from its diet. If feed is not chewed properly, broken down efficiently, or absorbed well in the digestive tract, the horse may consume enough feed but still lose condition.

Dental disease can reduce chewing efficiency, making it harder for the horse to break down hay and extract energy from forage. Parasite burdens can further reduce nutrient availability by increasing nutrient losses, irritating the digestive tract, and raising calorie demands.

Some horses may also struggle to maintain weight because of poor digestive efficiency, hindgut imbalance, illness, or age-related changes in nutrient utilization. In these cases, the problem is not always how much the horse is eating, but how effectively the nutrients in the diet are being digested, absorbed, and used by the body. ^[5][6]

In other horses, poor condition may reflect inadequate muscle development rather than insufficient body fat alone. Horses with poor topline or muscle loss may require improved protein quality and adequate intake of key amino acids to support muscle maintenance and conditioning.

Because multiple factors can affect body condition at the same time, identifying the primary reason your horse is underweight is an important step in choosing the right feeding strategy and nutritional support.

When to Call the Veterinarian

If your horse is losing weight unexpectedly, rapidly, or continues to lose condition despite adequate forage intake and appropriate dietary adjustments, it’s important to involve your veterinarian.

Weight loss can be associated with nutrition and management issues, but it may also reflect dental disease, parasite burdens, gastric ulcers, hindgut dysfunction, pain, or other underlying health problems.

Veterinary evaluation is especially important if your horse has any of the following signs:

• Ongoing or unexplained weight loss, especially when feed intake appears adequate
• Reduced appetite, slower eating, dropping feed, or difficulty chewing hay
• Loose manure, recurrent digestive upset or diarrhea
• Declining topline, muscle loss, or poor condition that does not improve with diet changes
• Lethargy, changes in attitude, or reduced performance alongside weight loss

Your veterinarian can help determine whether the problem is primarily nutritional or whether further evaluation is needed.

Factors that Limit Weight Gain in Horses

Not all horses who appear thin have the same nutritional problem. Some horses are not consuming enough calories to maintain body condition, while others may struggle with poor feed utilization or inadequate muscle development.

These categories can also overlap, meaning some horses may benefit from calorie support alongside digestive or amino acid support depending on their individual needs.

Insufficient Calorie Intake

Many underweight horses are simply in a calorie deficit, meaning they expend more energy than they consume. This is common in hard keepers, senior horses, exercising horses, and other horses with higher energy requirements.

Calorie deficits can develop gradually when forage quality is poor, meal sizes are too small, feeding frequency is limited, or workload and environmental demands exceed the energy supplied by the diet.

Cold weather, heavy training, lactation, growth, and stress can all increase calorie requirements beyond what some horses consume voluntarily.

Common signs of inadequate calorie intake include: ^[6][7]

• Visible ribs or hip bones
• Difficulty maintaining weight
• Weight loss during winter or heavy work
• Poor body condition despite adequate forage access

In these situations, increasing calorie intake is usually the priority. This often involves improving forage quality, increasing total forage intake, or adding calorie-dense feeds and fat supplements to help the horse maintain a healthier body condition without relying excessively on large grain meals.

Digestive Inefficiency & Poor Feed Utilization

Some horses consume adequate calories but still struggle to maintain condition because they are not efficiently digesting or utilizing nutrients from the diet.

Digestive efficiency is influenced by various factors, including:

• Stress
• Abrupt dietary changes
• Hindgut microflora imbalance (dysbiosis)
• Aging
• Inconsistent forage intake
• Illness

In these horses, the issue may not be how much feed is offered, but rather how effectively nutrients are extracted from the diet and utilized.

These horses may show signs such as: ^[5][8]

• Poor condition despite eating well
• Loose manure or inconsistent manure quality
• Reduced feed efficiency
• Difficulty maintaining weight during stress

In these cases, supporting digestive health alongside a weight gain supplement may help horses better maintain body condition by improving feed efficiency and nutrient utilization.

Management strategies such as improving forage consistency, reducing stress, and optimizing feeding routines can also play an important role.

Probiotics, prebiotics, yeast, and digestive enzymes may help support hindgut microbial balance, fiber digestion, and overall gut function, making it easier for the horse to get more nutritional value from the diet over time.

Poor Muscle Development & Amino Acid Intake

Some horses appear underconditioned because they lack topline or muscle development, not because they need more body fat. These horses may have an acceptable body condition score but still appear narrow, weak over the topline, or poorly muscled through the back and hindquarters.

In many cases, these horses consume adequate calories but may not receive enough high-quality protein or key amino acids needed to support muscle maintenance and protein synthesis. Workload, aging, forage quality, and conditioning can all influence how effectively horses maintain muscle mass and topline.

Common signs include: ^{[7][9][10][11][12]}

• Poor topline development
• Muscle loss along the back or hindquarters
• Thin appearance despite adequate body fat
• Difficulty maintaining muscle while in regular work

In these horses, adding more calories alone may not fully address the problem. Building and maintaining muscle requires adequate exercise, high-quality protein, and key limiting amino acids such as lysine, methionine, and threonine.

Vitamin and mineral deficiencies can also contribute to poor muscle development. Nutrients such as vitamin E, selenium, magnesium, copper, zinc, and B vitamins support normal muscle function, antioxidant defenses, energy metabolism, and tissue repair. If these nutrients are missing or poorly balanced, the horse may struggle to develop topline even when calorie intake is adequate.

What to Look for in a Weight Gain Supplement

For most horses that need help gaining weight, the simplest and most effective option is a fat-based supplement such as Mad Barn’s w-3 Oil. It provides concentrated calories without relying on high-starch feeds or large grain meals, making it a practical choice for hard keepers, senior horses, performance horses, and any horses that need more energy in the diet.

A good weight gain supplement should help increase calorie intake while fitting into a balanced feeding program. For many horses, this means choosing a supplement that provides digestible, calorie-dense energy without adding unnecessary starch, sugar, or feed volume.

Nutritionists recommend looking for a weight gain supplement that provides:

• Enough calories per serving to meaningfully support weight gain
• Calorie-dense fat, which supplies more energy per gram than carbohydrates or protein
• Low-starch energy to reduce reliance on grain, sweet feeds, or large concentrate meals
• Digestible energy that does not contribute to gut issues or reactive behavior
• Good palatability so the supplement is readily eaten by picky horses or horses with reduced appetite
• Compatibility with a balanced feeding program, including adequate forage, protein, vitamins, minerals, water, and salt

This is why w-3 Oil is the best overall weight gain supplement for horses that primarily need more calories. It supplies fat-based energy along with omega-3 fatty acids and natural vitamin E to support body condition while keeping starch intake low.

Some horses need more than calorie support alone. If your horse is eating enough but still struggling to maintain weight, poor digestion, low forage quality, inadequate protein, or an unbalanced diet may also be involved. In those cases, digestive support or targeted amino acid supplementation may be needed alongside a calorie-dense supplement.

Fat as a Calorie Source for Horses

Fat is one of the most effective ways to increase calorie intake in horses because it provides a concentrated source of dietary energy without relying heavily on starch or grain-based feeds. ^[13][14]

Compared to carbohydrates, fat contains significantly more calories per gram, allowing horses to consume more energy without substantially increasing meal size. This can be especially useful for hard keepers, senior horses, and performance horses with higher calorie requirements. ^[1]

Fat-based calories are often described as “cool calories” because they provide energy without the excitability sometimes associated with high-starch feeding programs. Increasing dietary fat may also help reduce reliance on large grain meals. ^[14][15]

Common fat sources used in equine diets include vegetable oils, stabilized rice bran, flax products, camelina oil, and high-fat commercial feeds or supplements.

Oils rich in omega-3 fatty acids may provide additional nutritional benefits while supporting overall calorie intake and healthy body condition.

Because fat is highly calorie-dense, even relatively small feeding amounts can significantly increase total dietary energy intake. This makes fat-based supplements particularly useful for horses that need additional calories but may struggle to consume larger volumes of feed.

W-3 Oil: Best Overall Weight Gain Supplement

For most horses that need additional calories, Mad Barn’s w-3 Oil is the best overall weight gain supplement because it provides a high-calorie, low-starch way to support body condition.

A 100 gram serving of w-3 Oil provides approximately 900 calories from fat, making it an efficient option for horses that need more energy without larger grain meals or extra feed bulk. This is especially useful for hard keepers, senior horses, performance horses, and horses that do not tolerate high-starch concentrates well.

Unlike plain vegetable oil, w-3 Oil is formulated to provide more complete nutritional support. It supplies fat-based energy from a blend of flax oil and soybean oil, with added DHA and natural vitamin E.

DHA is a long-chain omega-3 fatty acid that helps support normal inflammatory balance, joint health, skin and coat quality, immune function, and overall wellness. This makes w-3 Oil an ideal choice for horses in work that need weight management support along with the broader benefits of omega-3 supplementation.

w-3 Oil also contains high levels of natural vitamin E, an important antioxidant that helps protect cell membranes from oxidative stress. This is important because adding unsaturated fat to the diet increases the horse’s need for antioxidant protection. Horses on higher-fat diets require adequate vitamin E to support normal muscle function, immune function, tissue health, and recovery from exercise.

This combination of concentrated calories, DHA, and natural vitamin E makes w-3 Oil a more complete way to add fat to the diet than feeding plain oil alone. It is also palatable, cost-effective, and easy to incorporate into most feeding programs.

W-3 Oil is ideal for horses that need:

• More calories to support weight gain or weight maintenance
• Low-starch energy without relying on grain, sweet feeds, or large concentrate meals
• DHA omega-3 fatty acids to support joint health, skin and coat quality, immune function, and normal inflammatory balance
• Natural vitamin E to support antioxidant protection when adding fat to the diet
• A practical daily supplement that is palatable, cost-effective, and easy to feed consistently

For best results, w-3 Oil should be fed as part of a balanced diet that provides adequate forage, protein, vitamins, minerals, water, and salt to support healthy body condition over time.

Visceral+: Best Supplement for Appetite and Stomach Support

Some horses struggle to maintain weight because they are not consuming enough calories to meet their energy needs. This can occur when horses have a reduced appetite, inconsistent feed intake, or underlying digestive discomfort that affects their willingness to eat.

The horse’s stomach is a common source of abdominal discomfort which can contribute to poor appetite, ‘picky eating’ and reduced feed intake. ^[16][17] When horses consistently consume fewer calories than required, maintaining body condition and supporting healthy weight gain becomes more difficult.

Mad Barn’s Visceral+ is the best supplement for horses that need support for appetite, gastric function, and abdominal comfort. Visceral+ helps maintain a healthy stomach environment and supports normal digestive function, which can improve abdominal comfort and feed intake.

Visceral+ helps support appetite and stomach health by providing:

• Lecithin that helps maintain the protective lining of the stomach
• Nucleotides that support healthy gastric tissue and normal tissue repair processes
• Glutamine that serves as an energy source for cells of the digestive tract
• Mannan-oligosaccharides that support mucin production in the gut

This type of support can be especially useful for horses with poor appetite, inconsistent eating habits, signs of gastric discomfort, stressful lifestyles, or difficulty maintaining body condition despite access to adequate feed.

For horses that require additional calories for weight gain or to support high workloads, Visceral+ can be used alongside w-3 Oil.

Together, these supplements help support healthy weight gain by increasing calorie intake and supporting gut health to encourage adequate feed intake.

Optimum Digestive Health: Best Supplement for Feed Efficiency

Some horses consume enough feed but still struggle to maintain condition because they are not efficiently digesting or utilizing nutrients from the diet. In these cases, the horse may be eating enough, but extracting less energy and nutrition from that feed than expected.

Much of the energy a horse uses comes from hindgut fermentation. Microbes in the cecum and colon break down fiber from hay and pasture into volatile fatty acids (VFAs), which the horse absorbs and uses as an energy source.

When hindgut microbial balance is disrupted, fiber digestion and nutrient utilization can become less efficient. As a result, the horse may extract less usable energy from the diet, making it harder to maintain weight and body condition.

Mad Barn’s Optimum Digestive Health is the best supplement for horses that need support for feed efficiency, nutrient utilization, and hindgut function. Rather than supplying calories directly, it supports the digestive environment that helps horses make better use of the forage, feed, and supplements already in the diet.

Optimum Digestive Health helps support digestive function and feed efficiency by providing:

• Probiotics to help maintain a healthy population of beneficial hindgut microbes
• Prebiotics that serve as a food source for beneficial bacteria and support microbial activity
• Yeast and fermentation products to support fibre-digesting bacteria and normal hindgut fermentation
• Digestive enzymes to help break down feed components and support nutrient availability
• Toxin binders to help reduce the impact of undesirable compounds that may interfere with normal digestive function
• Ingredients that help maintain hindgut stability during stress, dietary change, travel, or inconsistent forage intake

This type of support can be especially useful for horses with inconsistent manure quality, reduced feed efficiency, stress-related digestive challenges, or difficulty maintaining condition despite apparently adequate feed intake.

For horses that need additional calories, Optimum Digestive Health can be used alongside a weight gain supplement such as w-3 Oil.

This combination supports both sides of the problem: w-3 Oil increases digestible energy intake, while Optimum Digestive Health supports the digestive function needed to better utilize the overall diet.

Three Amigos: Best Supplement for Muscle Development

Some horses appear thin or underdeveloped because they lack topline and muscle mass, not because they need more body fat. These horses may have an acceptable body condition score but still look narrow, weak over the back, or poorly muscled through the hindquarters.

In these cases, adding more calories alone may not solve the problem. Muscle development requires an appropriate training stimulus, enough dietary energy to support growth, and adequate protein intake. Protein quality also matters, because horses need sufficient essential amino acids to build muscle protein.

Amino acids are called “limiting” when they are in shortest supply relative to the horse’s needs. If one essential amino acid is too low, the horse cannot efficiently use the rest of the protein in the diet for muscle building.

This means a horse may be eating enough total protein but still lack the specific amino acids needed to support topline, muscle repair, and lean tissue development.

Mad Barn’s Three Amigos is the best supplement for horses that need targeted amino acid support for topline and lean muscle development. It provides lysine, methionine, and threonine, the three most commonly limiting essential amino acids in equine diets.

Three Amigos helps support condition and muscle development by providing pure amino acids in an optimal ratio:

• Lysine: The primary limiting amino acid in many equine diets and a key nutrient for muscle protein synthesis
• Methionine: Supports protein synthesis, tissue development, hoof quality, and methylation pathways involved in normal metabolism
• Threonine: Supports muscle protein synthesis, gut barrier function, immune function, and normal tissue maintenance

Three Amigos is especially useful for horses with poor topline, higher protein requirements, or diets based heavily on mature hay or lower-quality forage.

How to Choose the Right Weight Gain Supplement

The best weight gain supplement for your horse depends on what is primarily limiting body condition, weight maintenance, or muscle development. Some horses simply require more calories, while others may need better digestive support or improved amino acid intake to fully utilize the diet.

Many horses benefit from a combination approach. For example, a hard keeper in heavy work may require both additional calories and amino acid support, while a senior horse may benefit from increasing calories alongside digestive support. ^[1][9]

Choose a high-calorie fat supplement such as W-3 Oil when:

• Your horse struggles to maintain weight or body condition
• Calorie intake needs to increase to support weight gain
• Your horse has higher energy requirements because of workload, age, or physiological status
• You want to increase calories without relying heavily on starch or grain
• You want additional omega-3 fatty acid and natural vitamin E support for joints, skin health and more

Choose digestive support such as Optimum Digestive Health when:

• Your horse is eating adequate energy but still struggles to maintain condition
• You want to improve feed efficiency or nutrient utilization
• Your horse has inconsistent manure quality or digestive challenges
• Stress or digestive imbalance may be affecting feed utilization
• You want additional support for hindgut function and digestive health

Choose digestive support such as Visceral+ when:

• Your horse has low or fluctuating appetite
• You want to improve abdominal comfort
• Your horse is at high risk of gastric ulcers
• You want additional support for stomach and intestinal health

Choose targeted amino acid support such as Three Amigos when:

• Your horse lacks topline or muscle development
• Calorie intake appears adequate but muscle maintenance is poor
• Protein quality or amino acid intake may be limiting conditioning
• Your horse requires additional support for muscle recovery or development
• Your horse appears narrow or poorly muscled rather than truly underweight

Because several factors can affect body condition at the same time, evaluating the full diet and feeding program is often the most effective way to identify the right nutritional strategy for your horse.

Reviewing forage intake, calorie supply, protein quality, digestive health, and overall nutrient balance can help determine whether your horse primarily needs additional calories, digestive support, amino acid support, or a combination of these approaches.

Table 1. Weight gain supplement comparison

Final Recommendations

The best weight gain supplement for your horse is the one that addresses the primary nutritional factor limiting body condition and weight maintenance once medical issues have been ruled out.

For most horses needing additional calories, W-3 Oil is the best overall choice because it provides calorie-dense fat, omega-3 fatty acids, and natural vitamin E to support body condition without relying heavily on starch or grain-based feeds.

Horses that are eating adequately but still struggle to maintain condition may benefit from Optimum Digestive Health to support feed efficiency and nutrient utilization.

Horses with poor topline or inadequate muscle development may benefit from Three Amigos, which supplies the key limiting amino acids required for muscle maintenance and conditioning.

Targeted supplements can be useful in many situations, but they should complement a balanced feeding program rather than replace proper forage intake, calorie balance, and overall diet management.

For personalized guidance, submit your horse’s diet for a free evaluation by Mad Barn’s equine nutritionists to identify nutritional gaps and determine the best feeding strategy for healthy weight gain and body condition support.

Frequently Asked Questions

Here are some frequently asked questions about weight gain supplements for horses:

Summary

Weight gain in horses depends on consuming enough calories while also supporting forage intake, protein quality, digestion and overall nutrient balance. It's important to rule out underlying medical causes of weight loss or poor body condition before adding feed or supplements.

• W-3 Oil is the best overall choice for horses that need calorie-dense fat to support body condition without relying on large grain meals.
• Optimum Digestive Health may benefit horses that eat enough feed but still struggle to maintain condition because of poor feed efficiency.
• Three Amigos provides targeted amino acid support for horses that lack topline or lean muscle development despite adequate calorie intake.
• The right supplement depends on whether the horse primarily needs more calories, better nutrient utilization or improved amino acid intake.
• Unexplained weight loss or poor condition should be discussed with a veterinarian to rule out dental disease, parasites, pain or other health concerns.