What Causes Horses to Lose Weight and How to Fix the Problem

Last updated: May 7, 2025

By: Miles HenryFact Checked

Is your horse losing weight and you don’t know why? You’re not alone. Many horse owners face this challenge at some point, often despite feeding high-quality hay, grain, and supplements. Weight loss can be subtle at first, but it’s usually a sign that something deeper is going on, from dental issues and parasites to poor digestion or chronic stress.

As someone who’s owned and trained horses for years, I’ve dealt with this firsthand. One of my mares started losing weight out of nowhere—her appetite was fine, and her energy seemed normal. But after digging deeper, I discovered dental issues and underlying stress that took time to uncover and fix. I’ve since learned how many hidden causes can contribute to weight loss, even in otherwise healthy-looking horses.

In this guide, I’ll break down the most common reasons horses lose weight, how to spot the early warning signs, and what you can do—step by step—to get your horse back to a healthy weight. Whether your horse is a hard keeper, recovering from illness, or just not filling out the way they should, you’ll find practical answers here.

Understanding the Underlying Issues: Why Weight Loss Isn’t Always Simple

Weight loss in horses occurs when the calories they expend exceed the calories they consume. But identifying why this energy imbalance is happening isn’t always straightforward. It can stem from a variety of factors—some obvious, like inadequate feed, and others more hidden, like chronic pain, parasites, or metabolic disorders.

Addressing weight loss effectively requires more than just feeding more hay or grain. It takes careful observation, a systematic approach, and often the insight of a qualified veterinarian. The American Association of Equine Practitioners (AAEP) emphasizes the importance of thorough evaluation, as weight loss can be one of the first signs of a more serious underlying health issue.

Let’s take a closer look at the most common reasons horses lose weight—and how to recognize the early warning signs before the problem worsens.

Why Is My Horse Losing Weight? 5 Common Causes Explained

Weight loss in horses can result from various factors, some overt and others more insidious. Understanding these causes is crucial for effective intervention. Below, we delve into the most prevalent reasons horses lose weight, highlighting specific signs to watch for and actionable steps you can take.

Cause	Key Symptoms	Quick Action Step

Dental issues

Quidding, slow eating

Schedule float

Parasites

Dull coat, pot belly

Fecal egg count

Stress

Weaving, poor sleep

Adjust turnout, calming aids

1. Dental Issues: The Foundation of Efficient Digestion

How it Leads to Weight Loss:
Proper chewing is essential for breaking down feed, particularly fibrous roughage such as hay. Dental problems—such as sharp enamel points, uneven wear, or missing teeth—can make chewing painful and inefficient. This leads to reduced feed intake, incomplete digestion, and ultimately, weight loss.

Specific Symptoms to Watch For:

• Quidding: Dropping partially chewed balls of feed.
• Slow or reluctant eating.
• Excessive salivation.
• Head tilting or tossing while eating.
• Undigested feed in manure.
• Gradual weight loss.
• Poor Body Condition Score (BCS).
• Dropping grain while eating.
• Foul odor from the mouth.

What You Can Do:

• Observe Chewing Habits: Monitor for signs of discomfort while eating.
• Examine the Mouth: Safely inspect for obvious dental issues.
• Schedule a Professional Dental Exam: Annual dental check-ups by a qualified equine dentist or veterinarian are crucial.
• Dietary Adjustments: Offer softer feeds, such as soaked hay cubes or senior feeds, until dental issues are addressed.

For more information on equine dental care, refer to the AAEP’s Introduction to Equine Dentistry.

2. Parasites in Horses: A Hidden Cause of Weight Loss

How it Leads to Weight Loss:
Internal parasites, including roundworms, tapeworms, and strongyles, can deprive your horse of essential nutrients by damaging the digestive tract and interfering with nutrient absorption. Heavy infestations can significantly impact a horse’s ability to maintain weight.

Specific Symptoms to Watch For:

• Dull coat.
• Pot belly, especially in young horses.
• Tail rubbing.
• Lethargy.
• Poor growth in young horses.
• Diarrhea.
• Rapid weight loss in severe cases.

What You Can Do:

• Implement a Strategic Deworming Program: Collaborate with your veterinarian to develop a deworming schedule based on fecal egg counts.
• Practice Good Pasture Management: Regularly remove manure, rotate grazing areas, and avoid overstocking.
• Monitor Fecal Egg Counts: Regular testing helps determine parasite load and the effectiveness of your deworming program.
• Isolate New Arrivals: Quarantine new horses and perform fecal tests before introducing them to your herd.

For comprehensive strategies on managing equine parasites, consult Penn State Extension’s guide.

3. Dietary Issues: The Fuel Imbalance

How it Leads to Weight Loss:
Insufficient calorie intake, poor-quality feed, or an imbalanced diet can contribute to weight loss. Even if a horse consumes adequate volume, if the feed lacks necessary nutrients or is not easily digestible, weight loss can occur.

Specific Symptoms to Watch For:

• Persistent hunger.
• Lethargy.
• Poor coat condition.
• Gradual weight loss.
• Poor muscle tone.
• Changes in manure consistency.

What You Can Do:

• Evaluate Your Horse’s Diet: Ensure the type and amount of hay, grain, and supplements align with their age, workload, and individual needs.
• Assess Hay Quality: Poor-quality hay with low nutritional value won’t provide sufficient calories. Consider having your hay analyzed. Learn about selecting hay for horses.
• Increase Caloric Intake Gradually: Introduce calorie-dense feeds, such as stabilized rice bran, beet pulp (soaked for easy digestion), or oils (like flaxseed or corn oil), under veterinary guidance.
• Ensure Adequate Forage: Horses require 1.5–2% of their body weight in forage daily.
• Consult an Equine Nutritionist: For persistent weight loss or specific dietary needs, seek professional advice.

For detailed information on equine nutritional requirements, refer to the Merck Veterinary Manual.

4. Underlying Medical Conditions: When Weight Loss is a Symptom

How it Leads to Weight Loss:
Various medical conditions can interfere with a horse’s ability to eat, digest, or absorb nutrients. Conditions such as Pituitary Pars Intermedia Dysfunction (PPID or Cushing’s disease), inflammatory bowel disease (IBD), or chronic infections can lead to weight loss.

Specific Symptoms to Watch For:

• Lethargy and depression.
• Changes in appetite.
• Fever.
• Coughing or difficulty breathing.
• Changes in drinking or urination.
• Chronic diarrhea or colic.
• Poor performance.
• Rapid or gradual weight loss.
• Unusual lumps or bumps.
• Changes in coat, such as a long, curly coat that doesn’t shed properly (indicative of PPID).

What You Can Do:

• Schedule a Veterinary Examination Immediately: Unexplained weight loss can signal serious underlying conditions. A thorough veterinary examination, including bloodwork and other diagnostics, is essential.

For more information on PPID, refer to the Royal Veterinary College’s fact sheet.

5. Stress and Environmental Factors: The Hidden Energy Drain

How it Leads to Weight Loss:
Chronic stress from social dynamics, intense training schedules, frequent travel, or uncomfortable living conditions can increase a horse’s metabolic rate and reduce appetite, leading to weight loss over time.

Specific Symptoms to Watch For:

• Behavioral changes: increased anxiety, stall walking, weaving, cribbing.
• Decreased appetite or picky eating.
• Poor sleep quality.
• Increased heart rate or respiration at rest.
• Gradual weight loss.
• Increased susceptibility to illness.

What You Can Do:

• Evaluate Living Conditions: Ensure your horse has a comfortable environment with adequate space, shelter, and ventilation.
• Assess Herd Dynamics: Observe interactions and address any bullying or social stress.
• Manage Training Schedules: Provide adequate rest and recovery time appropriate for their workload.
• Minimize Travel Stress: Implement strategies to reduce stress during transportation.
• Maintain a Consistent Routine: Horses thrive on routine; maintain consistent feeding, turnout, and exercise schedules.
• Consider Calming Aids (if needed): For horses with high stress levels, some calming supplements, such as magnesium-based blends or adaptogenic herbs, can be helpful. Always consult your vet before use.

*For insights into managing equine stress, check out my article Understanding Stress in Horses.

How to Spot the Early Signs of Weight Loss in Horses

Weight loss often creeps up slowly, especially in horses with thick coats or when they’re not handled daily. Catching the problem early can make all the difference in recovery. That’s why routine monitoring and body condition scoring are essential.

One of the most reliable tools is the Henneke Body Condition Scoring (BCS) system, which evaluates fat coverage on a scale of 1–9. A drop of even one point can be a critical early warning sign. 👉 Want to track weight more accurately? Check out my article on How to Measure a Horse’s Weight: Tools and Techniques for easy, reliable methods—no scale required.

Also watch for these early red flags:

• Decreased Energy or Performance – This can happen when the body is conserving energy due to insufficient calorie intake or underlying illness.
• Changes in Appetite or Eating Habits – If your horse is eating slowly, picking at hay, or leaving feed behind, they may not be consuming enough calories.
• Dull or Rough Coat – A lackluster coat often signals nutrient deficiencies, which are closely tied to weight loss and poor condition.
• Changes in Manure – Loose, overly dry, or manure containing undigested feed may suggest digestive issues that limit nutrient absorption.

📝 Tip: Keep a monthly log of your horse’s weight, body condition score, coat appearance, and appetite. Noticing trends early can help prevent small changes from turning into major setbacks.

Step-by-Step Action Plan: Getting Your Horse Back on Track

1. Observe and Document Carefully
Take stock of your horse’s overall health, behavior, appetite, manure, and environment. Document everything you notice—even small changes in weight, energy, or eating habits can offer valuable clues.

2. Rule Out Obvious Issues
Start with the basics: visually inspect the teeth (if safe to do so), check your horse’s recent deworming history and fecal egg count results, and evaluate the current feeding program. Poor hay quality, imbalanced rations, or excessive alfalfa intake can sometimes contribute to the problem.

3. Consult Your Veterinarian
If the cause isn’t obvious—or if your horse shows signs of illness—schedule a veterinary exam promptly. Share your notes with your vet to support a faster and more accurate diagnosis.

4. Follow the Vet’s Recommendations
Stick closely to any diagnostic or treatment plans your vet outlines, whether that includes blood work, dental care, or medication.

5. Implement Smart Management Changes
Be prepared to adjust your horse’s feeding plan, dental routine, parasite control, and even their turnout or social environment based on professional guidance. For example, I had success helping my mare regain weight by cutting back on alfalfa (which reduced gut irritation) and adding a daily probiotic supplement—a surprising but effective combo that made a noticeable difference.
👉 You can read more about that approach in my article: Equine Probiotics: Boosting Horse Health & Performance.

6. Monitor Progress Over Time
Track your horse’s weight and Body Condition Score (BCS) weekly or monthly using a visual log or photos. While minor improvements may be noticeable within a couple of weeks, significant weight gain or condition improvement often takes several weeks to a few months, depending on the underlying cause and how early it was caught.

7. Seek Help from an Equine Nutritionist
If weight gain is still elusive after making initial adjustments, consult a qualified equine nutritionist. A tailored feeding plan can make all the difference, especially for senior horses or hard keepers.

Wondering how long weight gain might take? Every horse is unique, but recovery can be a gradual process. Check out my article on How Long It Takes to Put Weight on Your Horse (7 Steps That Work) for a realistic timeline and additional tips to support long-term progress.

With patience, consistency, and the right support team, many horses bounce back from weight loss and thrive. The key is to stay proactive and tailor your approach to your horse’s unique needs.

Expert Insight: Understanding Why Your Horse Is Losing Weight

Want to hear directly from a veterinarian? In this video, a licensed equine vet answers common questions about why a horse might be losing weight, what warning signs to watch for, and when to call your vet. Topics include dental issues, parasites, ulcers, and metabolic conditions—all explained in clear, practical terms.

Watch now to gain professional insight and learn how to approach equine weight loss concerns with confidence.

FAQs: Why is My Horse Losing Weight?

Still have questions? Below are answers to some of the most common concerns horse owners have about unexpected weight loss—and how to address them effectively.

Conclusion: Weight Loss in Horses—Don’t Wait to Investigate

Unexplained weight loss in horses isn’t just a cosmetic concern—it’s often the first visible sign of a deeper health or management issue. Whether it’s due to dental pain, parasites, stress, or poor digestion, catching the problem early can make all the difference.

By staying observant, tracking your horse’s body condition, and working closely with your veterinarian (and a nutritionist if needed), you can uncover the cause and take proactive steps to help your horse regain a healthy weight and thrive.

💡 Remember: Subtle weight changes may be easy to overlook, but your horse’s long-term health depends on your vigilance and timely action.

Call to Action (Enhanced for Engagement & SEO):

Have you noticed unexplained weight loss in your horse?
Share what helped (or what didn’t) in the comments below—your story could help another owner spot the signs earlier. And if you’re unsure about your horse’s condition, don’t wait: contact your veterinarian for a proper diagnosis and care plan tailored to your horse’s needs.