Poop’s Gettin’ Real: Fecals and Deworming

Keeping your horse healthy is the poo. So here’s the dish on your horse’s poo and deworming.


When I was a child — or even a young adult, for that matter — if you had told me that I would spend a significant portion of my time concerning myself with poo, I would have laughed you out of the room. But the truth is, as a parent and horse owner, I now spend a lot of time worrying about poo. I won’t regale you with parenting poo prose, but as fellow horse people, you know that worrying about your horse’s poo is just part being responsible for its care.

Is my horse pooping enough? Is its poo too dry? Is it too runny? Is it the right color? The list goes on (especially if you’ve ever spent a few hours concerned with colic — then you worry about poo a lot). One important addition to that list is how poo comes into play with assessing and treating parasites.

The Past

How horse owners and barn managers approach deworming can vary from location to location. But the issue is that many commonly used strategies for parasite control in adult horses are based on information that is 50 years old. For instance, in the 1970s, the internal parasite that was the biggest threat to horses was the large strongyle or bloodworm. As a defense, health experts introduced the interval program — all horses on a farm were treated with a rotation of wormers on a set schedule.

The good news? That approach was effective. Thanks to the interval program, bloodworms are incredibly rare.

The bad news? Now we have other parasites with which to contend — ones for which interval deworming is not effective.

Today the most common equine parasite is the small strongyle (Cyathostome). Interval deworming programs do not seem to affect the prevalence of this parasite in horse populations, so a different approach to parasite control is required. Unfortunately, many horse owners are still treating their horses based on the practice that was introduced in the 70s.

More bad news? Due to constant deworming, parasites are developing a resistance to the chemicals used to kill them.

According to the American Academy of Equine Practitioners (AAEP), frequent anthelmintic (medicine used to treat parasites) treatments are not what adult horses need to stay healthy. What is needed are “properly timed treatments with effective anthelmintics administered at the appropriate time of year, which correspond to the epidemiological cycles of transmission and the relative parasite burdens in individual horses.”

Translation: Assess each horse as an individual and treat it with the correct dewormer.

The Present

So, what’s the best way to treat adult horses and keep their parasite counts low? The current recommendation is that horses should only be treated if they show signs of a heavy parasite load. Most healthy adult horses develop immunity to parasites (meaning they don’t get as many). Horses with a high level of immunity don’t shed many eggs, so deworming all horses on the same schedule makes little sense. Why would you treat a horse with a light parasite load in the same way that you would treat one with a heavy parasite load?

This is where our obsession with our horses’ poo comes into play.

A fecal egg count is when your vet’s office examines your horse’s feces to determine the type of eggs being passed per unit weight of feces (e.g., eggs per gram, or EPG). Fecal egg counts are used to identify the moderate and high egg shedders (the horses carrying heavier parasite loads) for deworming. The moderate and high egg shedders are the horses that should be treated more aggressively — low shedders don’t necessarily need to be treated. High shedders almost certainly need more than one or two treatments a year, whereas low shedders likely need only one or two treatments a year at most.

The benefits of fecal egg counts are twofold: first, they allow you to tailor the treatment for each horse based on the level of egg shedding, thus reducing the overall amount of dewormers used (which means you save time and money!). Secondly, by closely monitoring effectiveness of treatments, you will be able to tell when a particular deworming agent has lost its effectiveness on your farm.T

A Case Study

Well, sort of a case study. More like an anecdote to illustrate the point.

Even though the benefit of deworming horses based on fecal egg counts may seem like old news to many horse owners, quite a few are still relying on interval deworming. When a discussion with fellow horse owners turned to deworming, I was surprised by how many of my seemingly well-informed equestrian colleagues don’t deworm their horses based on fecal egg counts. This discussion occurred at nearly the exact same time my barn was getting its results from our vet (it is spring, after all). I realized that my barn is a perfect example of why fecal egg counts are necessary.

To give you an idea of the scenario, the barn where I board has three pastures with small herds. Pasture A has two mares — a 20-something retiree and a two-year-old filly; Pasture B has three adult geldings; Pasture C has four adult mares. Here are the results of their fecal exams:

Pasture A

  • Senior mare: EPG of 525
  • Two-year-old filly: EPG of 1250

Pasture B

  • Gelding one: EPG of 0
  • Gelding two: EPG of 275
  • Gelding three: EPG od 0

Pasture C

  • Mare one: EPG of 375
  • Mare two: EPG of 750
  • Mare three: EPG of 1200
  • Mare four: EPG of 225

The variation in the results of the horses at my barn is a perfect illustration of how high shedders and low shedders exist in the same fields and why individualized treatment is necessary.

Of course there were some outliers — one horse was new to the barn and had been treated before he was turned out with other horses (so it makes sense that his count was 0) and the filly is still young and has yet to develop parasite resistance that adult horses often develop.

Getting a Fecal Egg Count

Fortunately, having a fecal egg count done is easy. In the case of my barn, when our vet comes to the barn for scheduled spring and fall shots, her technician collects a fecal sample from each horse and takes it to the clinic for examination. For those who don’t have the convenience of a vet who does routine farm calls, the process still is simple: scoop two fresh fecal balls from the center of the manure pile into a Ziploc bag that has been labeled with the date, owner and horse’s name. Squeeze the air out of the bag before sealing, and place the bag in the refrigerator if the egg count will not be done immediately.

Fortunately, having your vet do a fecal examination isn’t expensive — and that’s not something you hear very often in the horse world! Of course prices will vary from practice to practice, but our vet charges approximately $25 per fecal. If that means less administration of dewormer and healthier horses overall, I’m in!

For more information, refer to the AAEP’s Parasite Control Guidelines.

Canva/Nataliia Yankovets/CC