Pasture Management

Pasture Management For Horses And Parasite Control

Proper pasture management for horses is both a vital part of maintaining a healthy horse and an ongoing battle!

Well Managed Pasture - White Horse

Misguided owners think that turning a horse out to grass will provide adequate nourishment. Sadly, all too often the grass is on poor quality land and has been overgrazed.

Horses need quality grazing, seeded with nutritional grass mixtures, well fertilised and kept free of noxious weeds. Soil types and location determine the type of herbage and grasses that will flourish on your land.

Turning your horse out and forgetting him for days on end, is sure to result in a sick and depressed horse.

Leaving a horse alone in a field is unnatural because horses are herd animals needing companionship to thrive. Donkeys, goats and small ponies all make excellent companions for horses.

Good Hygiene Practices Are Essential To Keep Pasture Healthy. 

Parasite infestations are a problem on all horse grazing. 

Keep fields clean and safe with routine measures such as rotation, faeces removal and fence mending.

Simply turning your horse out into a weed and parasite infested, open field is a sure way to own a sick or dead horse. Worm infestations can lead to colic, bloat, ulcers, lung and even heart problems.

Fungal spores and bacteria thrive in mud harbouring nasties such as mud fever. Rainwater dripping from trees can cause rain scald.

Horses need shelter, water, mud-free areas and clean feed buckets.

Avoid Continuous Infestation With Proper Pasture Management

The horse worm life cycle starts with the ingestion of larvae or eggs from the grass. They mature through several stages into adult egg-laying worms in the horse. The eggs are passed out of the horse in the faeces onto the pasture. The eggs then hatch into fresh larvae.

This revolving cycle means new infestations continuously occur.

It is almost impossible to completely clear pasture of all types of worm. Drastically reduce infestation by adopting the following sensible control measures.

Mucking Out Is An Essential Part Of Pasture Management For Horses

The removal of all horse manure is an essential chore. it should be done at least twice weekly. Remove the faeces completely from the composted pasture.

Horse manure left in a heap in the corner of the field provides a breeding nursery for worms.

Care should be taken to add layers of agricultural lime between the layers of horse faeces to hasten decomposition and destroy the worm larvae. Otherwise, you will be providing a perfect breeding ground for worm and fly larvae, especially pesky stable flies.

Stable flies are the intermediate hosts to small stomach worms Habronema spp.

The point of infection is when worm larvae, emerging from the flies, touch the horse’s lips when feeding. The infective larvae are swallowed, taking up residence in the stomach mucosa where they cause lesions and ulceration.

Horseflies are often the cause of persistent summer sores and blisters around the muzzle, due to the bacteria they carry.


Harrowing is only useful during the dry spells with hot temperatures, in mid-summer (July & August over 25 degrees Celsius).

This will expose the worm larvae to the hot sun, temperatures over 25 degrees Celsius are fatal to worm larvae.

Warm, wet spells in Spring and Autumn favour worm eggs hatching. Worm larvae survive low temperatures in winter by hibernating until Spring when they become infective.

Harrowing at any other time of year is a futile waste of time, as you will be spreading the infective larvae across the land.

Past History & Companion Animals

Your pasture may have been contaminated by other animals.

Try to find out the history of your field or paddock. Trichostrongylus axei infect ruminants such as cattle, sheep and goats as well as horses.

These worms cause chronic catarrhal gastritis of the stomach, diminishing the horse’s ability to digest and absorb feed.

Repeated infestations can cause painful lesions leading to stomach ulceration. Horses become afraid to eat anticipating the discomfort, with foals being particularly susceptible to stomach worms.

Donkeys are host to lungworms Dictyocaulus arnfield. Up to 70% of donkeys carry lungworms often showing no clinical signs of infestation. Lungworms can overwinter in pasture unaffected by low temperatures.

Grazing horses ingest infective larvae that migrate to the lungs via the lymphatic system, and the pulmonary arterial blood supply. Larvae travel from the alveoli to the bronchi and bronchioles where they mature. The eggs are coughed up then swallowed and expelled in the faeces. Lungworms appear every summer once contaminated.

Many horses who are hypersensitive to dust from hay and straw have suffered lung damage as foals due to lungworm. Foals are particularly susceptible to this pest with long-lasting lung damage.

Treat all companion animals, not just horses, for worms. New animals bring increase risks of further infestations and therefore wormed before being introduced to the pasture.

Rotational Grazing & Pasture Contamination

A high density of horses per acre increases the worm count and puts real pressure on effective pasture management. Overgrazing forces horses to graze on rough patches of grass that they usually leave for dunging. Inevitably, this leads to re-infestation and high worm counts.

Rotational grazing will help to control the build-up of parasites. The amount of acreage per horse/pony is dependent on the amount of supplementary feed provided, and the availability of winter grazing. 

A pony would need one and a half to four acres, an average adult horse three and a half to five acres, split into three or four separate paddocks. Many horses, particularly those in livery stables, have considerably less than three acres. As a result, fields become contaminated with high levels of parasite infestation.

Pasture management for horses and associated parasitic infestation can be naturally controlled through a combination o good pasture management for horses and a sensible regime of natural horse wormer application.

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