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Why do a Fecal Egg Count?


Why do a Fecal Egg Count?

The Problem: 

Parasites are becoming resistant to current de-worming products.  De-worming products are becoming less effective because of this.   

Horsehealth can be adversely affected with a heavy parasite burden (colic, chronic coughing, poor keeper, poor performance, unthrifty, internal organ damages, etc…)   


How has this happen? 
Over use of de-worming products 
Inappropriate use of de-worming products 
Not knowing what parasites were present when de-worming 
Deworming according to the calendar 
Treating all horses the same when de-worming  

Many other factors affecting grazing practices and pasture management 



What can we do? 

Performing fecal egg counts on a regular basis and tailoring your deworming program based on these results is the single most important thing you can do to improve your parasite control strategy. 

Treat with the right drug, at the right dose, at the right time, in the right horse.  


What is the ultimate goal of any deworming program? 

To reduce parasite reproduction and contamination of the environment 


Interesting facts 

20% of the horses harbor 80% of the parasites 

Worming according to the calendar encourages parasite resistance. 

Not all horses are equally susceptible to parasite infection. 

Removing feces from the environment before eggs become infective provides parasite control that is superior to deworming. 

New additions to a herd can introduce resistant strongyles to a previously “clean” population. 

More than 150 different parasites can infect horses (only a small number pose a real problem for horses) 

The most important parasites (the big 4) to target are round worms, Large and small strongyles and tape worms. 

Younger horses are more prone to problems associated with parasites and should be treated differently than adult horses. 

The active ingredient in dewormers influences the interval between deworming times 

Horses pastured with donkeys are more likely to harbor lung worms and should be treated accordingly 


Pasture management practices that may help. 

Rotate pastures 
Do not overcrowd pastures 
Plant annuals such as winter wheat 
Rotate livestock species in pastures when possible 
Quarantine and deworm all new horses prior to introduction to the heard 
Remove feces from grazing areas on a regular basis (every few days) 
Avoid feeding from the ground 

Harrow pastures only when climatic conditions (hot summer temps) will kill the developing parasites  

Leave freshly dragged pastures empty for several weeks to allow the weather to kill the maximum number of parasites. 


There are three classes of dewormers 

Benzimidazoles (FenbendazoleOxibendazole) 

Pyrantel (Strongid) 

Macrocyclic lactones (IvermectinMoxidectin) 


How to make sure the proper dose is given 

Here is a way to estimate your horse’s weight 

Measure heart girth (directly behind elbow) 

Measure body length (from point of shoulder to point of buttocks) 

girth X girth X length ÷ 330 = body weight 


Consult your veterinarian if there are any questions concerning your horse’s fecal egg count results and recommendations about your deworming program 



Egg reappearance period 

Moxidectin- 12 weeks 

Ivermectin- 8 weeks 

Pyrantel- 4 to 6 weeks 

Benzimidazoles- 4 weeks 


Classifications of shedders 

Low egg shedders <200 eggs per gram of feces deworm?  no 

Moderate egg shedders 200 to 500 eggs per gram of feces deworm?  maybe 

High egg shedders >500 eggs per gram of feces deworm?  Yes 

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