Horse Worming and Managing Pasture

Managing PastureIn the wild, horses roam freely over thousands of acres with continuous access to cleaner pasture. Worms and horses evolved together in this environment, developing a relatively ‘healthy’ balance. Domesticated horses tend to be kept more intensively on restricted grazing, which exposes them to worm re-infection at a much greater level and upsets the balance of the horse/worm dynamic. Our job as horse owners is to re-establish this balance by controlling the amount of worms our horses are exposed to by managing pasture.

Reducing the number of worms on the pasture will help to keep the re-infection challenge to a minimum. This in turn reduces our reliance on wormers, hopefully slowing the development of resistance to them.

Tips for good pasture management

  • Remove droppings, ideally at least twice a week
  • Rest the pasture for at least three months a year to reduce the worm challenge. Sunlight and hard frost should help reduce the larval numbers so, if you can, choose the time of year carefully.
  • Combine harrowing with resting. Harrowing dirty pasture can just spread the worm eggs and larvae over the field, but if combined with pasture resting it can be of benefit.
  • Cross grazing the pasture with cattle or sheep will help reduce the worm challenge to the horses. They will ‘hoover-up’ the worms without being affected as the worms are host-specific.
  • Don’t over-stock paddocks as the quality of grazing will suffer.
  • Reduce paddock size so that you can alternately rest and graze your fields.


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