Deworming the Difficult Horse


    Many of us have gone up against the horse that’s nearly impossible to deworm, and it isn’t fun. You stealthily approach with the tube of dewormer hidden behind your back, reassuringly stroke your horse’s neck and say some soothing words to him. But as soon as you flash that white tube, his lightning-fast reflexes do you one better and he lifts his head out of reach or throws the afterburners into reverse. A battle of wills ensues, and nobody wins.

    Isn’t there an easier way? The answer is yes—with training. Woodrow Friend, DVM, of Rood and Riddle Equine Hospital in Lexington, Ky., has personally owned one of these difficult horses, and has assisted many clients with them. Here are some of his tips for making deworming easier.

    “Start out by sticking treats in the corner of your horse’s mouth as a distraction technique,” says Friend. This will get him munching happily and focusing on you as a treat-giver so you can slide the dewormer tube into his mouth while he’s preoccupied.

    “If that doesn’t work, the horse needs to gradually learn to get more ‘friendly’ with his head when the syringe comes out,” continues Friend. “Try filling an empty deworming syringe with corn syrup so he associates it with being a treat. Once he’s friendly with the syringe from the corn syrup treat, switch to dewormer.” You’ll need to periodically switch back to corn syrup so your horse doesn’t become resentful again.

    Easier Deworming
    One product specifically designed to facilitate deworming a difficult horse is the Easy Wormer made by Miracle Corp. This bit applicator and headstall allows you to insert the deworming paste into his mouth through the hollow side opening (see slideshow). This may be a good alternative if the other methods aren’t working.

    Some dewormers also feature ergonomically designed applicators that are easier to grip and administer.

    General Deworming Tips
    Assuming your horse now calmly accepts dewormer, some general tips apply. To make sure your horse is being properly dosed, find out his approximate weight by using a weight tape. This should give you a number within 100 pounds or so, which is sufficient enough for setting the dose on the deworming tube. According to most syringes, horses weighing over 1,250 pounds will need part of a second tube to get the appropriate dose.

    If you have a problem with your horse spitting out his dewormer after you administer it, try thoroughly flushing his mouth out with a hose first. Dewormer can easily adhere to bits of hay and grass that remain in the back of his mouth, even long after a meal. Most deworming products adhere very well to the tongue and mouth as long as there isn’t loose food to help expel the paste.

    Working on your horse’s behavior and involving your vet are the two best ways to ensure your horse is dewormed effectively. Keeping him parasite-free will help prevent health problems, such as colic, that can result from a heavy worm burden.

    Work With Your Vet
    Recent advances in deworming research emphasize how big of a problem parasite resistance to deworming drugs has become. Since there are only a finite number of deworming chemicals available, it’s critical that horse owners do everything possible to avoid making resistance worse.

    The new research recommends a strategic deworming approach tailored to each individual horse. To determine the most appropriate deworming schedule, ask your vet about fecal egg counts (FECs) and fecal egg count reduction tests (FECRTs). These help to identify which horses on the farm need deworming, which products to use, and how often to use them.

    Further Reading
    Horse Deworming Tutorial Video
    New Thinking on Deworming
    Deworming the Reluctant Horse

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    Holly Caccamise, Editor
    Holly Caccamise has been with Horse Illustrated and Young Rider magazines since 2007, and in 2019, she became Editor in Chief of both titles. Caccamise has a master's degree in...


    1. Good advice in teaching a horse to accept the syringe. However, most horses I know would most definitely have aversion to being hosed in the mouth! It seems that would be very hard to desensitize.

    2. I agree that the hose in the mouth is sort of taking it too far. That would definitly make my horse even more scared of the syringe. with my old horse i would put dewormer on a cookies and get her used to the taste that way.

    3. I don’t care for this article. I use desensitization techniques from Clinton Anderson. The first step is to not sneak up on your horse with the syringe. That is the worse thing you can do. Walk right up to your horse with the dewormer right in front of you. You should first be able to wave the syringe all around your horse’s head with her cooperating and standing still relaxed. Next, you should be able to touch the horse with the syringe. DO NOT put it in their mouth. Then, once the horse accepts it touching them, put it in the corner of their mouth, but DO NOT release any of the medicine. This will let the horse know that something in their mouth does not mean a bad taste! Then, you can give the horse the dewormer. This process may take a few days but I promise it works. I used to fight with my mare for hours, but now it only takes a minute or two. She doesn’t like deworming, but she accepts it.


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