July 2021 - Equine Deworming Q&A
Written by courtesy of Valley Vet Supply
Friday, 02 July 2021 02:15
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Veterinarians offer answers to deworming FAQs

courtesy of Valley Vet Supply

Equine deworming is a critical part of overall equine wellness. It’s also a rather technical part of your horse’s wellness program. Find answers to equine deworming FAQs, from veterinarians and Valley Vet Supply co-founders, Drs. Arnold Nagely and Ray Shultz.


Q: What risks do parasites present to horses?
Parasites rob horses of nutrition, energy and overall wellness. When left untreated, parasites can cause critical damage to a horse’s vital organs, impair their growth, hinder their performance and even cause colic.

Q: When is the best time to deworm my horse?
American Association of Equine Practitioners (AAEP) parasite control guidelines recommend that adult horses be dewormed in the spring, at the beginning of grazing season, and in late fall/early winter, toward the end of grazing season.

Q: How often should adult horses be dewormed?
Work with your veterinarian to perform a fecal egg count (FEC) test, which will help guide you on the frequency of deworming treatments needed. The AAEP recommends one FEC per year for adult horses.  As a general best practice, though, horses should be treated once or twice yearly, during spring and fall, but there can be specific cases and stabling environments requiring more frequent deworming treatments.

Q: According to a horse’s FEC results, what constitutes as a low or high parasite shedder?
Low shedder: 0 to 100 eggs per gram (EPG)
Moderate shedder: 200 to 500 EPG
High shedder: 600 to 3,000 EPG

Q: Which parasites should horses be treated against?
There are more than 150 species of internal parasites that can infect horses. The following are the most common, with the first three posing the greatest risk to your horse’s health.
  • Small strongyles (cyathostomins)
  • Roundworms (ascarids)
  • Tapeworms
  • Large strongyles (bloodworms or redworms)
  • Pinworms
  • Bots
  • Threadworms
Q: Can certain factors contribute to increased parasite levels at a barn?
A number of elements can contribute to higher levels of parasite shedding, such as:
  • Boarding and training barns, which house greater numbers of horses that may contribute to increased parasite burden
  • Movement of horses on and off the farm for training or competitions, presenting greater contact with other horses
  • Foals, weanlings and geriatric horses, which are often higher shedders of eggs
  • High stocking densities (more than two horses per acre) and nonrotated pastures, which are proven to increase parasite levels
Q:  Should a horse’s approximate weight be determined before dosing dewormers?
Yes, it is important to dose to your horse’s individual weight when deworming. Either reference an accurate weight captured from a digital scale at your horse’s veterinary appointment, or keep a handy weight tape in your tack box to help accurately dose your horse’s dewormer. Remember these four simple steps to using a weight tape.
  1. Make sure your horse is standing square.
  2. Place the weight tape around your horse’s heart girth.
  3. For the closest weight approximation, see the number where the tape meets.
  4. Set your dewormer to the correct weight to administer an accurate dose.
Q: What are best practices to incorporate for parasite control, in addition to deworming?
To better manage parasites, it is recommended that horses consume grain and hay from a feeder or hay rack that is elevated off the ground. Removing manure daily, as well as composting manure and clipping pastures, also can help control parasite populations. To help eliminate larvae, pasture rotation also is a best practice. If possible, horse owners can remove horses from the pasture and rotate in another species, such as cattle, to help eliminate parasite burden from the field.

You can find equine dewormers, as well as additional horse health information, at www.ValleyVet.com.