• Cassie Faull, DVM

Prevent Parasites With Pasture Management


A major threat to the health of sheep and goats is the barber pole worm, a gastrointestinal parasite. This parasite steals nutrients from its host and can cause significant anemia (blood loss), reduced animal production and, in severe cases, death. In addition to appropriate deworming strategies, proper pasture management can effectively control parasite exposure and reinfection.


The lifecycle of the barber pole worm provides the foundation on which pasture management strategies are built. The adult barber pole worm lives its life inside of the host, producing thousands of eggs daily that are shed in the fecal pellets of the goat or sheep as it gazes the pasture. Within 3-4 days, the eggs hatch and develop into the infective larval stage which migrate several inches up the blades of grass to be eaten by the next hungry grazer.

To help reduce your exposure to parasites, here are a few methods of pasture management and strategies to put in place when pasture rotation isn’t an option:

Make Your Pasture Work for You

Several methods of pasture management can be utilized to prevent exposure to the parasites and completion of their life cycle, including:

  • Rotational Grazing: Progressively moving livestock to new pasture greatly decreases the exposure of the to parasites.

  • Blade Length: The majority of parasite larva are located within the bottom three inches of the plant, therefore animals should be moved to a new grazing area before they graze to the three-inch height of the plant length.

  • Timing: The amount of time animals remain in one pasture as well as the time resting a contaminated pasture is important. Parasite eggs can hatch and reach an infective larval stage in 3-4 days, therefore exposure to infective larva can be decreased if the livestock are moved within 1-3 days. The parasite load will be especially dense in areas of where the sheep and goats congregate, usually near shade or a water source. Frequently rotating to new pasture will discourage this behavior and decrease exposure to areas of concentrated parasite larva.

  • Returning: Returning to a previously grazed pasture is another delicate but important part of rotational grazing. During ideal weather conditions, forage is typically ready to re-graze in 3-4 weeks, however this is about the same time that the larval population may reach their peak. A longer period of rest is recommended to prevent re-infection. In order to give the area an extended break from grazing without losing forage quality, the pasture may be harvested as hay.

Strategies When Pasture Rotation Isn’t Possible

Rotational grazing is an effective tool, but cannot be accomplished with all herds due to lack of land, fencing and time. Other pasture management strategies contributing to parasite control include:

  • Forage Browsing: Allowing animals to browse in a wooded area encourages them to eat forage higher off the ground, thus preventing exposure to parasites. Plants containing higher levels of tannins — sericea lespedeza (Chinese bushclover), pine bark, birdsfoot trefoil and black locust trees — can inhibit parasitic larval development and reduce fecal egg counts of barber pole worms.

  • Beauty Before Age: Young animals have very little immunity to internal parasites due to lack of exposure. They typically do not develop a robust immunity until around 4-9 months of age making them especially susceptible to parasitism. Allowing a young group to graze an area ahead of a group of mature animals will decrease the exposure of parasites to the younger, more susceptible group.

  • Leader-Follower System: In general, sheep and goats do not share the same gastrointestinal parasites as cattle and horses. The infective larval stage of the barber pole worm cannot complete its life cycle after it is ingested by cattle or horses. Therefore grazing sheep and goats on the taller grass first, then allowing cattle and/or horses to follow and graze the remaining few inches of grass can help manage internal parasites by “cleaning up” the pasture before the sheep and goats return to re-graze.

Barber pole worms have developed a profound resistance to most of the deworming medications available, and in order to preserve the effective dewormers that we currently have, other methods of parasite control must be considered. With some planning, pasture management can be a helpful tool in controlling your herd’s exposure to parasites.


© Old Dominion Veterinary Services.

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