Fecal Egg Count Monitoring: Using Data to Drive Parasite Decisions

Let the Data Tell You When to Deworm

Fecal egg counts (FEC) transform parasite management from guesswork to science. Instead of deworming on a calendar or waiting for visible problems, FEC testing tells you when treatment's actually needed and whether your dewormer's still working. As resistance becomes more common, this kind of information is only getting more valuable.

This guide explains how to collect samples, interpret results, and use FEC data to make better decisions for your herd.

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What Fecal Egg Counts Tell You

What FEC Measures

Number of parasite eggs per gram of feces (EPG)
Provides estimate of adult worm burden
Identifies which parasites are present
Tracks changes over time

What FEC Doesn't Tell You

Exact worm numbers (it's an estimate)
Immature/arrested larvae (they don't produce eggs)
Damage already done
Individual animal immunity status

Value of FEC Testing

Purpose	Application
Diagnosis	Confirm parasites causing problems
Monitoring	Track herd parasite status over time
Treatment decision	Determine if/when treatment needed
Efficacy testing	Verify dewormer is working
Resistance detection	Identify failing products early

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Sample Collection

When to Collect

10-14 days after treatment (efficacy check)
Mid-grazing season (monitoring)
Fall before housing (season summary)
During peak egg output fluctuation
When animals are stressed

Which Animals to Sample

Select randomly from the group
Include range of body conditions
Focus on age groups of interest
Suspected clinical cases
Valuable animals needing monitoring

Collection Procedure

Sample bags or containers (labeled)
Cooler with ice packs
Marking materials (tags, paint)
Collection sheet
Don clean glove
Collect fresh feces directly from rectum
Approximately 10-20 grams needed (golf ball size)
Place in clean, labeled container
Keep cool immediately
Record animal ID and any notes
Avoid freezing
Submit to lab within 24-48 hours
Record collection date/time

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Testing Methods

McMaster Technique

Detects eggs per gram (EPG)
Detection limit varies (typically 25-50 EPG)
Consistent and reproducible

Modified Wisconsin

Often used when high accuracy needed
More labor intensive
Good for efficacy testing

FLOTAC

Research standard
Less commonly available
More expensive

Where to Get Testing

University diagnostic services
Some private labs
On-farm kits (less accurate but useful for trends)

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Interpreting Results

Understanding EPG Numbers

|-----------|----------------|--------| | 0-200 | Low | Monitor, may not need treatment | | 200-500 | Moderate | Consider treatment, especially in young stock | | 500-1000 | High | Treatment recommended | | >1000 | Very high | Immediate treatment needed |

Context matters (animal age, condition, timing)
Some animals tolerate higher levels
Species of parasite affects interpretation

Species Identification

Some parasites more harmful than others
Treatment selection may vary
Resistance patterns differ by species

|----------|--------------| | Ostertagia | Most damaging to cattle | | Cooperia | Very common, less pathogenic | | Haemonchus | Blood-feeding, more harmful | | Nematodirus | Important in calves | | Liver flukes | Require specific treatment |

Individual vs. Herd Results

Subject to day-to-day variation
Most useful for clinical cases
Provides average for group
Less expensive than many individual tests
Loses individual variation information
Shows variation between animals
Identifies high shedders
Most informative but most expensive

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Fecal Egg Count Reduction Test (FECRT)

Purpose

Determine if your dewormer is working effectively.

Protocol

|-----|--------| | Day 0 | Collect fecal samples from 10-15 animals | | Day 0 | Record EPG results | | Day 0 | Treat entire test group with dewormer | | Day 10-14 | Collect follow-up samples (same animals) | | Day 10-14 | Record EPG results | | Compare | Calculate percent reduction |

Calculation

``` FECRT % = ((Pre-treatment EPG - Post-treatment EPG) / Pre-treatment EPG) × 100 ```

Post-treatment average: 40 EPG
FECRT = ((400-40)/400) × 100 = 90%

Interpretation

FECRT Result	Interpretation
>95%	Highly effective
90-95%	Effective, monitor for changes
80-90%	Possible early resistance
<80%	Resistance present

When to Perform FECRT

After any suspected treatment failure
When changing operations/cattle source
When changing dewormer products

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Using FEC Data for Decisions

Treatment Threshold Approach

Set treatment thresholds (e.g., >500 EPG)
Test at key times
Treat only when threshold exceeded
Verify treatment success
Reduces unnecessary treatments
Maintains refugia
Saves money when not needed

Identifying High Shedders

May benefit from selective treatment
Some operations cull chronic high shedders
Protects refugia in low shedders
Identifies animals with poor immunity

Seasonal Patterns

Track year-to-year changes
Correlate with weather patterns
Identify peak risk periods
Pasture rotation planning
Budget planning
Program refinement

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On-Farm Testing Options

Available Kits

Moderate accuracy
Learning curve for counting
Cost-effective for frequent testing
Smartphone apps with image analysis
Variable accuracy
Improving rapidly

DIY vs. Lab Testing

Factor	On-Farm	Lab
Cost per test	Lower (after initial equipment)	Higher
Accuracy	Variable	High
Turnaround	Immediate	Days
Species ID	Limited	Detailed
Equipment needed	Microscope, supplies	None
Best for	Routine monitoring	Baseline, FECRT

Building In-House Capability

McMaster slides ($50-100)
Supplies (floatation solution, etc.)
Training (vet/extension resources)
Use on-farm for routine monitoring
Verify on-farm results periodically with lab

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Record Keeping

What to Record

Animal ID(s) or group
Sample type (individual/composite)
Lab used or on-farm method
EPG result
Species identified (if available)
Treatment given (if any)
Notes on conditions

Tracking Over Time

Treatment dates and products
FECRT results
Weather/pasture conditions
Performance correlations

Using Records

Evaluate treatment effectiveness
Identify chronic problems
Adjust program as needed

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Frequently Asked Questions

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Bottom Line

FEC guides decisions - Data beats guesswork
Sample correctly - Fresh, cool, to lab quickly
Test for efficacy - FECRT tells you if products work
Context matters - Numbers need interpretation
Track over time - Patterns inform management
Combine with clinical - FEC supplements, doesn't replace, observation

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References

Coles, G.C., et al. (1992). World Association for the Advancement of Veterinary Parasitology (WAAVP) methods for the detection of anthelmintic resistance in nematodes of veterinary importance.
Texas A&M AgriLife Extension. (2024). Fecal Egg Count Testing for Cattle.
Kaplan, R.M. & Vidyashankar, A.N. (2012). An inconvenient truth: Global worming and anthelmintic resistance. Veterinary Parasitology, 186(1-2), 70-78.
USDA-APHIS. (2023). Parasite Diagnostic Methods for Livestock.
American Association of Veterinary Parasitologists. (2024). Guidelines for Fecal Examination.

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Article published by AnimalSafeRanch.com | Last updated: January 2026 Reviewed by: Licensed veterinarians and parasitologists