Click & Collect - from over 50 stores
Free Delivery - on orders over £250(T&C's Apply)
Trade Accounts - pay monthly credit terms

How to weigh a horse before worming and why it’s important

In our latest edition of horse worming advice, we look at how to weigh a horse and why it is so important. A report concluded by the British Riding Club has discovered that 44% of horse owners don't weigh their horses prior to worming. So why must we do it? without an accurate weight it is difficult to determine the dosage and can therefore result in either overdosing or underdosing. Either scenario is undesired and can be avoided very easily.


Wormers are administered orally, either by a syringe directly to the mouth or through the addition to food. The exact instructions can be found on the packaging and should be read carefully prior to administration.

If your horse appears off colour or you are concerned that you have overdosed, contact your local Vet immediately, ensure that you have kept the wormer packaging to provide exact information of the ingredients and usage advice.

Foals, horses with pre-existing health conditions and elderly horses are at greater risk of the effects of overdosing. Be aware that miniature breeds will have seperate dosage requirements and to follow instructions for that particular breed as they are also at risk. In rare situations, a horse can suffer an allergic reaction to a particular wormer.


Contrary to popular belief, underdosing can be more serious than overdosing. The active ingredient in wormers is designed to kill parasites and needs to be at the correct concentration before entering the body. If the dosage is too low, some of the parasite can survive.

So what are the consequences of a few worms surviving?

Surviving worms will now developed a resistance to the wormer, you are now helping to breed a population of worms that are resistant to the wormer, which in time will make future worming very difficult as treatments will not be as effective.

Weighing your horse and getting the correct dosage

To attain an accurate weight, it is advised that you use a weighbridge to measure your horse's weight. If you don't own a weighbridge, there are public weighbridges available which can accommodate your trailor or lorry. Determine your horse's weight by weighing the lorry or trailer with the horse and then without, subtracting the weight of the vehicle.

If a weighbridge is not available, the next most accurate method is to use weight tape, this allows you to calculate the horse's weight via formula. For less than £10 it is the most cost effective method.


For more information regarding worming products available at Wynnstay, speak to your local Equine Specialist.

Use our store locator to find your local store, click here.


© 2021 Wynnstay Group Plc