Worming your Horse

August is the horses’ birthday so it is time for all horse owners to give their horses a birthday present and worm them before the start of spring.

There is a lot of misinformation and confusion about how and when to worm your horse correctly and effectively. Questions about which products are best, how often to use them, and whether the need to rotate products is important are amongst the most frequently asked. Your Veterinarian is the best person to answer these questions and give you the best advice for your horse and its particular situation

There are also a number of management approaches that will help and these include collection of droppings, keeping stocking rates lower, paddock rotation, supplementary feeding and putting foals onto cleaner paddocks. Factors such as seasons, rainfall, paddocks available and number and type of horses will all affect the best way to approach management practices.

In combination with good management practices, horse owners should use an effective and appropriate worming product and regime. For wormers to effectively treat internal parasite burdens, every horse must be dosed with the appropriate amount of wormer according to their bodyweight. If horses are under dosed with wormer, the internal parasites are exposed to a sub-lethal amount of the drug. This may leave a population of worms that are able to tolerate the wormer causing resistant worms.

Studies have shown that horse owners and handlers tend to under, rather than overestimate their horse’s bodyweight. Most people underestimate weight by approximately 20%. This means that many horses may be unintentionally under-dosed with wormer simply because a more accurate weight estimation method has not been used. The weight can be calculated by using a weight estimation formula which you veterinarian is happy to talk to you about.


It is also very important to ensure that the horse wormer you are using is effective against all worms including tapeworm. Equine tapeworm can cause or influence a number of colic related conditions in the horse. The damaging effects of tapeworms vary from colic and diarrhoea, to ulcers in the gut and occasionally even death. Tapeworms can cause a “plug” in the gut and the badly damaged bowel can simply tear apart from the extreme pressure.


Worming is a complex issue and depends on many different issues so it is important to ensure that the worming regime suits you situation. It you are not sure the friendly staff at Gunnedah Veterinary Hospital are always more than happy to discuss your concerns with you.