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It may be time to break your herd’s deworming traditions

Evolve your deworming strategies to improve their benefits


“We shouldn’t deworm just for the simple sake of tradition,” said John Davidson, DVM, senior associate director, beef cattle professional services, Boehringer Ingelheim. “We deworm to positively impact the health, performance and efficiencies of the cattle under our care.”

When left untreated, parasites in cattle can negatively impact the immune system, reduce weaning weights, lower conception rates, alter carcass composition and decrease milk production.1,2,3,4,5

By carefully considering your herd’s production goals and implementing strategic deworming protocols, you can minimize burdens caused by parasites. The following management practices can help you develop a deworming program that contributes to enhanced herd performance:

Identify economically important parasites

“Before deworming, the most important thing to know is the population of parasites you’re dealing with,” stressed Dr. Davidson. “By identifying the types of parasites most prevalent in your herd, you can select a product that provides the most cost-effective protection.”   

Coproculture and standardized fecal egg-count reduction tests will tell you not only which parasites your herd is dealing with, but also about the effectiveness of your current deworming program. Your local veterinarian and an accredited diagnostic laboratory can help you incorporate these tests into your parasite control protocols.

Choose the most effective product for your herd

“All of the commercially available dewormers kill parasites. Where they differ is the spectrum of parasites covered as well as the duration of their ability to kill parasites,” said Dr. Davidson. “It is important to appreciate that no product is able to kill every stage of every parasite species that our cattle are exposed to, and the length of killing power among products varies.”

Most dewormers can be divided into two classes, depending on their chemical structure:

  • Benzimidazoles are white wormers that are administered orally. These short-acting products are generally very effective against adult worms and other intestinal parasites but have little residual killing power.   

  • Macrocyclic lactones have a longer duration of activity against a much broader range of parasite stages than benzimidazoles. These dewormers are available in both pour-on and injectable formulations.

Dr. Davidson advises producers to compare product labels, and to choose a dewormer that best protects against the parasites most prevalent in their herd, while paying particular attention to duration of activity, especially against economically important species such as the brown stomach worm (Ostertagia spp).

It’s also important to take into account when you’ll be deworming and how long each product provides adequate parasite protection. What’s convenient for you may not be most effective for the herd.

If cattle are going into a contaminated pasture or are going to be grazing for a long period of time, a long-lasting injectable dewormer is recommended, because each mouthful of grass the cattle consume could expose them to parasites.

However, if it’s late fall and there has already been a hard freeze, producers can get by with a shorter-acting dewormer, as immediate re-exposure is far less likely.

Break tradition with concurrent therapy  

“Deworming is a numbers game,” said Dr. Davidson. “When we’re talking about parasite populations, the efficacy and length of parasite control are important parts of the equation.  We’re not talking about hundreds or even thousands of parasites. Less efficacious products leave large numbers of parasites behind which continue to negatively impact cattle performance.”   

Concurrent therapy, or combination therapy, is the practice of using two or more dewormers of different classes. This multi-pronged approach allows producers to kill a greater percentage of the parasites present in their cattle herd.

If you’re looking to boost cattle performance and productivity, concurrent therapy may be an option for your herd. However, this practice is definitely not something to try without a conversation with your veterinarian. Only your veterinarian can determine if you need a plan for treating cattle with full doses of two or more products of differing classes.

Work closely with a local veterinarian

Developing deworming protocols should start with a call to your veterinarian. He or she can help you establish a program that takes into account your goals and your operation’s ability to help create sustainable and effective deworming protocols.


1 Wiggin CJ and Gibbs HC. Studies of the immunomodulatory effects of low-level infection with Ostertagia ostertagi in calves. Am J Vet Res 1989;50(10):1764–1770.

2 Wohlgemuth K and Melancon JJ. Relationship between weaning weights of North Dakota beef calves and treatment of their dams with ivermectin. Agri-Pract 1988;9:23–26.

3 McPherson WB, Slacek B, Familton A, et al. The impact of eprinomectin treatment on dairy cattle reproductive performance, in Proceedings. 44th Annu Meet Amer Assn Vet Parasitol 1999; abs. 28, p. 41.

4 Mills B. Beware of internal thieves. Ang J 2001;140–143. Available at:

5 Sanchez J, Dohoo I, Carrier J, DesCoteaux L. A meta-analysis of the milk-production response after anthelmintic treatment in naturally infected adult dairy cows. Prev Vet Med 2004;63(3–4):237–256.

©2020 Boehringer Ingelheim Animal Health USA Inc., Duluth, GA. All Rights Reserved. US-BOV-0053-202

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