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Effective Equine Pasture Management and Parasite Control

Maintaining horse health through comprehensive pasture management and vigilant parasite control is crucial. Different types of worms pose varied threats to equine health, necessitating specific management and treatment approaches. This article expands on effective pasture management strategies, discusses in detail the different types of equine worms and their impacts, and underscores the importance of using fecal egg counts (FECs) in designing an effective deworming program.

Understanding Equine Parasites

Equine parasites can cause a range of health issues, from mild irritation to severe life-threatening conditions. Here’s a rundown of the most common types of worms found in horses and the problems they can cause:

  1. Strongyles (Bloodworms or Redworms):
    • Large Strongyles: Cause severe damage by migrating through blood vessels, leading to thrombi and emboli, which can result in colic, weight loss, and anemia.
    • Small Strongyles: Their larvae encyst in the intestinal wall and can cause inflammation, diarrhea, weight loss, and protein loss upon emergence.
  2. Ascarids (Roundworms):
    • These are a concern especially in foals and young horses, causing respiratory issues, intestinal blockages, poor growth, and rough coat due to their migration through the lungs and large size.
  3. Tapeworms:
    • Can lead to ileal impaction and spasmodic colic due to their attachment at the junction of the small intestine and cecum.
  4. Bots:
    • Larvae attach to the stomach lining, causing irritation, ulcers, and potentially, stomach wall perforation.
  5. Pinworms:
    • Cause intense anal itching, leading to tail rubbing and potential skin infections.
  6. Threadworms:
    • Mainly affect foals, causing diarrhea and weakness, and are transmitted through the mare’s milk.

The Importance of Fecal Egg Counts

Fecal egg counts (FECs) are a critical tool in the management of equine parasites. They provide a quantitative measure of the worm burden within a horse and help identify which individuals are high shedders, thus requiring more aggressive or frequent deworming treatments. This targeted approach not only makes deworming more effective but also reduces the risk of developing resistance to dewormers.

Benefits of Fecal Egg Counts:
  • Targeted Treatment: FECs help in identifying horses that need treatment, avoiding unnecessary deworming of horses with low or no parasite burden.
  • Resistance Management: By minimizing the use of dewormers, FECs help prevent the development of drug-resistant parasite populations.
  • Cost Efficiency: Reduces the cost of parasite control by limiting the use of dewormers to only those horses that need them.
  • Health Monitoring: Regular FECs can track the effectiveness of the current parasite control program and highlight any need for adjustments.

It is important to remember that when we are doing the Fecal Egg Count we want to test before we deworm to see what kind of dewormers that we need to use. However, it is equally important that we make sure to do another Fecal Egg Count after we have dewormed to make sure that our dewormer was effective.

Implementing Strategic Deworming

The choice of dewormer and the timing of its application depend on the types of parasites present and the degree of infestation, as indicated by FEC results.

  • Ivermectin and Moxidectin: Effective against most types of worms except for tapeworms. Moxidectin is particularly effective against encysted small strongyles.
  • Pyrantel Pamoate: Effective against large strongyles, roundworms, and used in higher doses for tapeworms.
  • Fenbendazole: Used particularly for treating encysted small strongyles, though resistance should be monitored.
  • Praziquantel: Specifically targets tapeworms, usually combined with other dewormers for broad-spectrum control.

Pasture Management and Regular Monitoring

Alongside deworming, good pasture management reduces worm burden. This includes rotational grazing, avoiding overstocking, regular removal of manure, and maintaining clean watering and feeding areas.

Rotational Grazing

One of the most effective methods for maintaining healthy pastures and reducing parasite load is rotational grazing. By dividing the pasture into smaller areas and rotating horses through these sections, you allow forage plants to recover from grazing pressure, which improves their health and nutritional quality. Additionally, rotational grazing interrupts the life cycles of many parasites, as the eggs and larvae are left behind in the grazed sections and are exposed to the elements, which can decrease their viability.

Steps for Implementing Rotational Grazing:
  1. Divide Pastures: Use fencing to divide larger pastures into smaller paddocks.
  2. Control Grazing Time: Move horses to a new paddock when the grass is grazed down to about 3-4 inches. This prevents overgrazing, which can stress the grass and reduce root depth.
  3. Rest Periods: Allow each paddock to rest for at least 3 weeks before reintroducing horses. This break helps in the regrowth of grasses and the die-off of parasites.

Managing Manure

Parasite management closely ties with manure management because parasites often spread through fecal matter. Regular removal of manure from pastures greatly reduces the parasite burden.

Manure Management Tips:
  • Regular Collection: Remove manure from pastures at least twice a week, more frequently in smaller or more heavily used paddocks.
  • Composting: Compost manure to kill parasite eggs and larvae. Proper composting reaches temperatures that are high enough to destroy most parasites.
  • Avoid Spreading Fresh Manure: Never spread fresh manure on fields that will be grazed by horses, as this can redistribute parasite eggs and larvae.


Understanding the types of worms that can affect horses, their specific health impacts, and the importance of fecal egg counts is crucial for effective parasite control. By integrating strategic deworming with comprehensive pasture management and regular use of FECs, horse owners can ensure their horses remain healthy, reducing the impact of parasites on their overall well-being. Regular consultations with veterinarians allow for tailored approaches based on FEC results and specific pasture conditions, ensuring that control measures are both effective and sustainable.


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