When should I worm my horse?

scottie grazing, when to worm your horse
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Horses nearly always have a worm burden, meaning they nearly always have some parasitic worms in their digestive system. Controlling the worm burden is very important as a major worm burden can impact the health of your horse. It could be something which seems something minor, such as losing a bit of weight and condition. But they can also have serious health risks such as colic. Some conditions have a mortality rate of 50% and will the horse may recover, there can be permanent damage. Therefore it is important to have your horse on a worming programme.

What worms affect horses?

  • Redworm (small, large and encysted.)
  • Tapeworm
  • Pinworm
  • Roundworm

Proactive and Reactive Worming Programmes.

Worming used to be very proactive, advice being to worm every 6-12 weeks regardless. We then moved away from this to using certain wormers at certain times of year. However, using lots of wormers allows the worms to build up immunity over time.

So now the advice is moving to a more reactive method. There are now a few different testing methods available, such as worm egg counts, saliva and blood tests. Horses should be tested throughout the year, usually more regularly during the main grazing season. Horses with high results or regularly test slightly above average should be wormed. This means that most horses are wormed less often and therefore worms are less likely to build up immunity.

When to worm?

There is no one size fits all method for worming horses. All horses have different needs with young and old horses needing more regular worming. But this is a rough guide for the average horse.

March/April: Tapeworm

There are now blood and saliva tests available for tapeworm as this is not picked up in the worm egg count test. So you can test at this time for tapeworm and then only worm if the results suggest you need to. But many vets would still advise worming for tapeworm.

Use Pyrantel or Praziquantel.

April-September: Redworms, pinworms, roundworms

This will likely be when your horses are grazing the most. If you have just wormed for tapeworm you may not need to do anything for another 6-12 weeks. But you should either worm throughout this period or perform worm egg counts and worm those with higher burdens.

We usually worm for Tapeworm March/April which also works on most of these worms too. So we will do an egg count June/July time and go from there.

September/October: Tapeworm

This is another time to check for tapeworm. If you didn’t worm earlier this year for tapeworm you probably should now. But again, you could test and go from there.

Use Pyrantel or Praziquantel

December: Small encysted redworm

There is now a blood test available to test for this. But this is still relatively new so might not being readily available yet. So you should worm for small encysted redworm in December or after the first frost of winter.

This is one of the few wormers you really shouldn’t miss and small encysted redworm is probably the most dangerous to our horses.

Use Moxidectin or Ivermectin.

Do I need to do this all myself?

If, like me, you find this all a bit of a minefield, there are plenty of options out there to keep you on track.

Most yards, especially livery yards, will have a yard programme so all the horses are doing the same thing. This means you shouldn’t have to worry too much about what you should be doing and when as usually the yard owner will organise this for the entire yard. But it never hurts to be aware of what should be happening!

If you have your horses by yourself or have to be responsible for your own worming programmes, there are still plenty of options out there to support you. Many vets will offer a worming programme where they will remind you when to worm and will provide the correct wormers and tests. Alternatively, many testing companies offer worm packages. These will usually include tests at certain times of year and suggestions of what wormers to use.

Other considerations

While worming your horse at the right times with the right wormers is very important for their health. There are other things what should also be considered when it comes to worming horses.

Your horses weight

How much wormer you give your horse is determined by their weight. Before giving your horse a wormer you should check their current weight. Ideally we would all have access to a weighbridge which is by far the most accurate way to get our horses weight. But at the bare minimum you should use a weight tape to get a rough idea.

Manage your fields

Poo picking regularly and if possible, rotating your fields will help keep the number of worms in your grazing down. Ideally fields should be cleared of droppings at least once a week. But at the very least your horse should have plenty of areas in the field clear of poo. Sharing your grazing with other animals such as sheep can also keep the worm numbers down.

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