Effective Worming For your horse

Good pasture management and animal husbandry combined with regular worm counts and tests can help most horse owners to significantly reduce the number of worming doses they give their horses.

This reduced exposure helps to slow resistance developing to the chemicals as well as being better for our horses and the environment. Great when worming can be a stressful experience for both horse and human!


But if you do need to treat there are some important considerations to take into account to ensure worming is effective.

KNOW YOUR Horse's Weight

One of the golden rules of worming is to give enough chemical for the weight of the animal. Not doing so gives insufficient amounts of the active ingredient to kill the worms effectively while still exposing them to the drug and is one of the fastest ways to increase resistance.

Use a weigh bridge where possible or a weight tape to calculate this as accurately as possible. Research shows weight estimates by eye can vary as much as 30%.

Wormers are very safe drugs and so to overcome the challenges of estimating weight and giving sufficient dose, veterinary advice is to add 10% to a weight tape estimate when calculating wormer quantity.

Know your drugs

Not only is it important to know what the active ingredient is and why you’re choosing a particular wormer but it’s also useful to understand the way the drug is presented. The same active ingredient is often available in several different formats depending on the brand.

Most horse wormers come as a paste or gel to be syringed into the horse’s mouth, but some are also available in tablet or liquid form that can be added to the feed. Generally wormer syringes come in sizes to treat up to either a 600kg or 700kg horse while wormers in tablet form contain enough to treat a horse up to 800kg in weight.

Giving a syringe wormer

Calculate the correct dose and adjust the dial accordingly, being aware that you might need more than one pack for a large horse. Hold the horse’s nose still with one hand and with the other slip the syringe into the corner of the mouth, pushing the plunger in and directing the paste to the back of the tongue. You might want to do some training first to ensure your horse is comfortable to be handled in this way.

Despite the best preparation sometimes not all of the wormer hits the intended spot! A survey cited by the pharmaceutical company Virbac reported 70% of horse owners admit some difficulty in worming their horse with only 30% claiming to be successful every time. Try to estimate any spit out and compensate accordingly, remembering that the actual wormer in most syringes only amounts to a heaped teaspoon full, so any spilt drops could be significant.

Be careful to clean up any spillages afterwards. All wormers are essentially poisons, most are dangerous to aquatic life and all will have a negative effect on dung beetles and other microorganisms they come in contact with. Wherever possible bring the horse onto a surfaced area to administer the wormer so that it can be easily cleaned if necessary. Dispose of packaging carefully, preferably in a bin with a lid. Be especially careful using ivermectin which is toxic to dogs, particularly Collies, Old English Sheep Dogs and their related breeds and crosses.

Wormers  in Feed

Tablet and liquid wormers can be measured out into the feed. Just as we need to be aware of spit out in pastes we also need to ensure the horse eats the full dose of wormer. Fussy feeders might benefit from additional apples or carrots, a sprinkling of appetitive herbs like mint or a splash of molasses if they can tolerate the sugars or cider vinegar to help them eat up.

Give a Probiotic

Treating your horse for worms is important but worming drugs can cause imbalances in the gut bacteria which in turn can create their own problems. Using a probiotic at the same time can help you protect your horse when giving this medication and restore the balance by promoting the growth of good bacteria.


Contact Westgate Labs’ friendly SQPs for free independent veterinary approved worming advice to help you decide what is best for your horse.