Key Takeaways
- Fecal Egg Count (FEC) tests help identify parasite levels in horses and support targeted deworming programs.
- Most horses should have fecal testing performed at least once or twice per year.
- Spring and fall are generally the best times to conduct FEC tests.
- Seasonal weather patterns influence parasite activity and transmission.
- FEC testing helps reduce unnecessary deworming and slows the development of parasite resistance.
- Good pasture management and regular manure removal play an important role in parasite control.
Introduction
Parasite management is a critical part of horse health, yet traditional deworming practices have changed significantly over the past decade. Rather than automatically administering dewormers on a fixed schedule, many veterinarians now recommend a more targeted approach based on fecal egg count (FEC) testing.
A fecal egg count measures the number of parasite eggs present in a horse’s manure sample. This information helps determine whether a horse is a low, moderate, or high shedder and allows owners to make more informed decisions about deworming.
Understanding when to perform a fecal test—and how often—is essential for maintaining horse health while helping preserve the effectiveness of available deworming products.
What Is a Fecal Egg Count Test?
A fecal egg count is a laboratory test used to estimate the number of parasite eggs present in a horse’s manure.
The test primarily measures strongyle eggs, which are among the most common internal parasites affecting horses. Results are reported as eggs per gram (EPG) of manure.
FEC testing allows veterinarians and horse owners to:
- Assess parasite burdens
- Identify high-shedding horses
- Develop targeted deworming plans
- Monitor the effectiveness of parasite control programs
- Reduce unnecessary deworming treatments
Rather than treating every horse the same way, FEC testing provides a more accurate picture of individual parasite risk.
Why Timing Matters
Parasite populations fluctuate throughout the year based on environmental conditions, grazing habits, and weather patterns.
Temperature and moisture levels significantly influence the development and survival of parasite larvae on pasture. As conditions become more favorable, parasite transmission can increase, creating higher risks for grazing horses.
Performing fecal tests at strategic times of the year allows owners to identify changes in parasite activity before problems develop.
Testing too infrequently can allow parasite burdens to build unnoticed, while testing at the right times helps guide more effective treatment decisions.
Spring: One of the Best Times for FEC Testing
Spring is often considered the most important time of year for fecal egg count testing.
As temperatures warm and horses spend more time grazing, parasite activity begins to increase. Larvae that survived winter conditions can become active, creating renewed exposure on pasture.
Conducting an FEC test during spring helps:
- Establish a baseline parasite level
- Identify high shedders before peak grazing season
- Guide spring deworming decisions
- Reduce contamination of summer pastures
Spring testing allows horse owners to enter the grazing season with a clearer understanding of parasite risks.
Fall: Another Critical Testing Window
Fall is the second most commonly recommended time for fecal testing.
After a full grazing season, horses may have accumulated varying levels of parasite exposure depending on management practices and environmental conditions.
Testing in the fall helps:
- Evaluate parasite control success throughout the year
- Identify horses requiring treatment before winter
- Adjust management plans for the following season
Many veterinarians recommend performing FEC tests in both spring and fall to gain a more complete picture of annual parasite activity.
How Often Should Horses Be Tested?
The ideal testing frequency depends on several factors, including age, management practices, and previous FEC results.
In general:
Adult Horses
Most healthy adult horses benefit from testing one to two times per year.
Young Horses
Foals and young horses typically face greater parasite risks and may require more frequent monitoring.
High Shedders
Horses consistently identified as high shedders may require additional testing to monitor parasite levels and treatment effectiveness.
Your veterinarian can help determine the most appropriate testing schedule based on your horse’s individual circumstances.
Understanding FEC Results
Fecal egg count results are generally categorized into three groups:
Low Shedders
Typically fewer than 200 eggs per gram (EPG)
Moderate Shedders
Typically between 200 and 500 EPG
High Shedders
Typically greater than 500 EPG
These categories help determine which horses contribute the most parasite contamination to shared grazing areas.
Research has shown that a relatively small percentage of horses often account for the majority of parasite egg shedding within a herd.
This is why targeted treatment programs are often more effective than blanket deworming schedules.
How FEC Testing Helps Prevent Dewormer Resistance
One of the biggest reasons veterinarians encourage fecal testing is the growing concern around parasite resistance.
Overuse of deworming products has contributed to resistance in several common equine parasites. When dewormers are administered unnecessarily, resistant parasites are more likely to survive and reproduce.
FEC testing helps reduce this problem by ensuring treatments are only used when appropriate.
Benefits include:
- Fewer unnecessary treatments
- Improved long-term effectiveness of dewormers
- Better parasite control outcomes
- Reduced medication costs
Protecting the effectiveness of existing dewormers is becoming increasingly important for the future of equine health.
The Role of Pasture Management in Parasite Control
While fecal testing is valuable, it should be viewed as one part of a larger parasite management strategy.
Good pasture management can significantly reduce parasite exposure by limiting the number of infective larvae present on grazing land.
Effective practices include:
- Rotational grazing
- Avoiding overstocking
- Maintaining healthy pasture growth
- Removing manure regularly
Regular manure removal is particularly important because parasite eggs are shed in manure before developing into larvae that contaminate surrounding grass.
Reducing manure accumulation helps lower parasite pressure and supports healthier grazing conditions throughout the year.
Common Mistakes to Avoid
Several common mistakes can reduce the effectiveness of fecal testing programs.
These include:
- Testing only after problems appear
- Assuming all horses require identical treatment
- Ignoring pasture management practices
- Deworming without veterinary guidance
- Failing to follow up on high egg counts
A successful parasite control program combines testing, treatment, and management rather than relying on any single strategy alone.
Conclusion
Fecal egg count testing has become one of the most valuable tools in modern equine parasite management.
By identifying parasite burdens accurately and guiding targeted deworming decisions, FEC tests help improve horse health while reducing the risk of dewormer resistance.
For most horses, spring and fall provide the best opportunities for testing, though frequency may vary depending on age, management practices, and previous results.
When combined with sound pasture management and regular manure removal, fecal testing forms the foundation of a more sustainable and effective parasite control program.
Frequently Asked Questions
1. What is a fecal egg count test for horses?
A fecal egg count test measures the number of parasite eggs present in a horse’s manure sample and helps determine parasite burden.
2. When is the best time to perform a fecal test?
Spring and fall are generally considered the best times to conduct fecal egg count testing.
3. How often should horses have fecal testing?
Most adult horses should be tested at least once or twice per year, while young horses or high shedders may require more frequent monitoring.
4. Can a fecal test replace deworming?
No. Fecal testing helps determine when deworming is necessary but does not eliminate the need for parasite control treatments.
5. Does manure removal help reduce parasites?
Yes. Regular manure removal helps reduce pasture contamination and lowers the number of parasite larvae available for horses to ingest.
TL;DR
Fecal egg count (FEC) testing helps horse owners monitor parasite levels and create more effective deworming programs. Most horses benefit from testing in spring and fall, when parasite activity is most relevant. FEC testing supports targeted treatment, helps prevent dewormer resistance, and works best when combined with good pasture management and regular manure removal.
