Managing Your Parasites to Death

With only 5 percent of parasites living in cattle, that means 95 percent of the parasites on any given farm are calling the pasture home.1 With this kind of parasite load distribution, it’s vitally important that a producer implement a sound strategic deworming program to help ensure that he is not only cleaning up his cattle, but is also cleaning up his pasture. Left unchecked, these parasites will affect the performance of a herd, as well as eat into an operation’s bottom line.1

“We’ve known for years that parasite control is critical to a cattle producer’s profitability and is the most economically important practice in beef production,”2 says Joe Dedrickson, DVM, director, Merial Veterinary Professional Services. “In fact, parasitologists estimate that parasites cost U.S. producers more than $200 million each year.3 In addition to decreased production, diminished reproductive performance and lower weight gains, producers must also be concerned about extra days to market, compromised immune responses and poor body conditions that result from absent or inadequate parasite control programs.”1,4,5

Part of developing an effective protocol is determining the optimal time to deworm. Treating a herd in conjunction with seasonal grazing patterns and using a dewormer that is effective against adults and L4 larval stages will help reduce egg shedding and pasture contamination.5 Keeping the pasture top of mind is also critical to the success of a deworming program. Producers need to focus on deworming their cattle, as well as their pastures to decrease contamination and reinfection among the herd.6

“Because areas in the northern United States typically experience colder winters with more snow and freezing temperatures, there is often the misconception that parasites are killed off1,7 and spring deworming is unnecessary, but that couldn’t be further from the truth,” says Dr. Dedrickson. “In the northern half of the country, the first deworming should ideally take place in the late spring or early summer to help protect cattle from infective larvae on pastures and help reduce pasture parasite loads.8 Larvae that have reached the infective stage are fairly resistant to cold, will survive the winter and be available for ingestion when cattle are put on pasture for grazing.”1,7

It’s also important to implement a deworming program before animals appear parasitized. If you can see the physical signs of parasite build-up, it often means the parasites have already done damage to the animal.1

“Timing is critical to the success of any deworming program,” says Dr. Dedrickson. “Considerations should include when grazing season begins, age and category of the animals, type of operation and the grazing history of the pastures.5 Because every producer’s situation is unique, we recommend you consult with your veterinarian when developing a deworming strategy.”

Producers also need to be aware of how long their parasite control products really work. Dr. Dedrickson notes that it is a common misperception that these products protect cattle against parasites for the entire season. “On average, most endectocides provide broad-spectrum control for 14 to 28 days, depending on the product and the parasite.1,9 Thus, one spring deworming will simply not address the parasites in your herd or in your pasture and opens up your operation to continual parasite reinfection.1,5

“Veterinarians are a valuable source of information and will help ensure you are effectively managing your parasite burden. More important, though, consulting with your veterinarian will help you maximize your parasite control investment, resulting in improved herd health and performance, as well as profitability.”1,4,5

For more information about strategic deworming, contact your Merial sales representative.

1 Arseneau J. Parasite Control. Beef Health Management Course. University of Minnesota Extension Service. Lesson 4.

2 Lawrence JD, Ibarburu MA. Economic Analysis of Pharmaceutical Technologies in Modern Beef Production. Iowa State University. 2007. Available at: Accessed January 15, 2012.

3 Kvasnicka B, Torell R, Bruce B. Internal Parasites of Cattle. Western Beef Resource Committee. Cattle Producer’s Library. CL690. 2010. Available at: Accessed January 15, 2012.

4 Pence M. Deworming Cattle for Profit. University of Georgia College of Veterinary Medicine. Available at: Accessed February 9, 2012.

5 Miller J. Strategic Deworming. Louisiana State University. Department of Epidemiology. Available at: Accessed January 15, 2012.

6 Stromberg B, Averbeck G. What’s New for Parasite Control in Cattle. University of Minnesota. College of Veterinary Medicine. Available at: Accessed March 6, 2012.

7 Craig T. Impact of Internal Parasites on Beef Cattle. Journal of Animal Science. 1988; 66:1565-1569.

8 Courtney CH. Internal Parasites of Dairy Cattle. 30th Florida Dairy Production Conference Proceedings 1993:32-35.

9 Whittier D, Currin J. Current Strategies in Parasite Control in Virginia Beef Cattle. Virginia Cooperative Extension. 2009. Available at: Accessed March 8, 2012.

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