Missouri Ag Connection - The Skinny on Parasite Management for Horses

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The Skinny on Parasite Management for Horses
Missouri Ag Connection - 04/06/2020

As the grazing season begins, horse owners need to consider their parasite management strategies for their horses. Parasite management is more than just choosing which dewormer to buy from the feed store.

Parasites are found in the manure balls of horses after the horse has shed them from their intestines. Horses can then ingest those parasites by grazing on grass that has parasites on it or eating hay or grain off the ground in a manure dense area. In dry, hot, sunny conditions the parasites will use their energy reserves more quickly and ultimately die more quickly. Conversely, if weather is mild, wet, and the manure is shaded, parasites can live 6 months or more. Mild, wet summers like the summer of 2019 in Missouri provide optimal conditions for parasites to persist in pastures and re-infect grazing horses.

Having your veterinarian conduct fecal egg counts is the best way to use a prescribed approach to deworming horses. This practice will determine which type of parasites individual horses have and which horses tend to shed high numbers of the parasites back onto the pastures. These high shedding horses may need to be dewormed more frequently in order to control the spread of parasites onto pastures. A Fecal egg count should be conducted at least once a year. The type of parasites a horse is shedding will determine which type of deworming product that horse will need, if any.

Using oral dewormers should be done after the last hard frost in the spring and again after the first hard frost in the fall. The deworming in the spring will prevent horses from shedding internal parasites onto the fresh growing pasture while the deworming in the fall should kill any parasites the horse has picked up during the grazing season.

Managing manure distribution in pastures is another important step to reducing the parasite load in horses. Managing manure to reduce parasites can be accomplished by adequately stocking pastures, harrowing or dragging manure across pastures, composting manure, and rotating pastures. Overstocked pastures lead to manure build up and increased parasite load in the pasture and in the horses grazing it. Adequately stocking pastures, roughly 3 acres per horse in southern Missouri, is an important step to minimize manure build up. Removing manure from pastures may not be a very feasible option but harrowing manure during sunny, hot days to spread it out and break up the manure balls so that it can dry and heat up more quickly can help to reduce the parasite load. Also, composting manure from stalls or pens can be an effective way to kill parasites due to the increased heat built up inside the compost pile. Another very effective way to reduce parasite load in horses is by implementing a rotational grazing system. Ultimately, the most successful parasite control plan would include all of these practices to mitigate the accumulation of parasites in horse pastures.

For more information or assistance in developing a comprehensive parasite control plan, contact your veterinarian or Field Specialist in Livestock Elizabeth Picking with University of Missouri Extension at 417-256-2391 or at pickinge@missouri.edu.

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