Managing equine health requires a thoughtful approach and parasite control is an important area to address. Among the tools available to horse owners, the Modified McMaster fecal egg count (FEC) is one of the most practical and cost-effective methods for monitoring parasite burdens. FEC provides actionable insights that support targeted deworming strategies, protect the effectiveness of deworming products and ultimately promote healthier horses.
What Is a Fecal Egg Count?
A fecal egg count measures the number of parasite eggs present in 4 grams of a horse's manure. Most often, the test focuses on strongyle eggs, which come from adult worms residing in the large intestine. Strongyles are among the most concerning internal parasites due to their impact on digestion and nutrient absorption.
In the lab, manure is mixed with a flotation solution, placed under a microscope, and the number of eggs is calculated. Results are expressed as eggs per gram (EPG).
Why Fecal Egg Counts Matter
1. Targeted Deworming
For years, rotational deworming was the standard practice. However, this approach led to overuse of deworming products and widespread anthelmintic resistance. A FEC allows for an evidence-based and individualized approach to parasite management. Instead of treating all horses blindly and equally, fecal egg counts identify
- which parasites are present in the systems of each horse
- an approximate population level of the parasites
This information allows you and your vet to choose the right deworming product for each horse and detects the high shedders in the herd. The results will categorize each horse into one of the following:
- Low shedders: <200 EPG
- Moderate shedders: 200–500 EPG
- High shedders: >500 EPG
This classification helps identify which horses are most responsible for pasture contamination. The aim is not to eliminate all parasites but to keep levels low enough that they do not impair health or performance. For further understanding, consult your veterinarian.
2. Horse-Specific Insights
Not all horses carry the same parasite burden. Research shows that about 20–30% of horses shed the majority of parasite eggs in a herd. Identifying those individuals means fewer unnecessary treatments for low shedders.
3. Herd Health Monitoring
FEC results give valuable information at the herd level. If multiple horses are testing high, management practices may need attention — such as manure removal, pasture rotation, or stocking density.
When Should You Perform a Fecal Egg Count?
Timing often depends on regional climate and parasite life cycles. While fecal egg counts can be done at any time of the year, spring and fall are the most common times to have parasite burdens checked.
After an initial FEC and respective dewormer is given, any horses in the herd that have tested moderate to high shedders should be retested 7-10 days later to verify the effectiveness of the initial treatment.
Always consult your veterinarian for guidance tailored to your horse and environment.
Beyond Deworming: Nutrition and Management
From an equine nutritionist's perspective, parasite control is only one piece of the puzzle. Supporting a horse's immune system and digestive health makes them more resilient:
- Protein and amino acids support tissue repair and immune function.
- Trace minerals like copper, zinc, and selenium are essential for immunity.
- Forage-based diets maintain gut integrity.
- Pasture management — regular manure removal, cross-grazing with ruminants, and reduced stocking density — lowers parasite exposure. Explore equine nutrition products at The Mill to support overall horse health.
Frequently Asked Questions About Fecal Egg Counts
How often should you do a fecal egg count on your horse?
Most horses benefit from testing 1–2 times per year — spring and fall are common checkpoints. Frequency varies depending on age, management, and environment.
What does a fecal egg count tell you?
An FEC measures eggs per 4 grams (EPG) of manure, classifying horses as low, moderate, or high shedders. This guides targeted deworming and monitors treatment effectiveness.
Do all horses need to be dewormed?
Not always. About 20–30% of horses shed most parasites in a herd. With FEC results, owners can focus treatment on those horses and avoid over-treating others.
What is anthelmintic resistance and why is it important?
It's when parasites adapt to survive dewormers that once worked. Overuse has made resistance a global issue in horses. FECs help slow this trend by guiding selective treatments.
Can nutrition help reduce parasite loads in horses?
While nutrition does not replace parasite control programs, a balanced diet can strengthen the immune system and gut health, making horses more resilient.
How do you collect a sample for a fecal egg count?
- Contact the Mill location nearest you to arrange a day and time to drop off samples
- Use fresh manure (less than 12 hours old but the fresher the better)
- Collect sample, using an inside-out Ziplock bag, from the center of a manure pile where the sample is less likely to be contaminated by its surroundings
- Label the bag with your name, the horse's name, the date and time the sample was collected
- If not immediately bringing into one of The Mill's 8 store locations, refrigerate the sample. DO NOT FREEZE
- Results will be provided typically within a week's time
- Discuss the results with your veterinarian to determine the best product for your individual horse's
- Pick up your dewormer at The Mill
Key Takeaways
- Fecal egg counts are a critical diagnostic tool for informed parasite management.
- They help reduce unnecessary deworming, preserve product effectiveness, and provide horse-specific insights.
- Pairing FECs with balanced nutrition and smart management supports long-term herd health.
By incorporating fecal egg counts into your routine care, you are not only protecting your horse today — you are also safeguarding the effectiveness of parasite control for the future.
