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The sweet spot for extended-release deworming

Using an extended-release dewormer can offer several benefits to a cattle operation, but it’s not right in every situation.

Submitted by Boehringer Ingelheim Vetmedica

Using an extended-release dewormer can offer several benefits to a cattle operation—higher average daily gains, improved reproduction and shorter calving intervals to name a few1,2—but it’s not right in every situation.

The right deworming protocol depends on the time of year, operation type, geography and the specific parasite challenges in a herd. To see if an extended-release dewormer is right for your operation, talk with your veterinarian and consider the following.

Current dewormer options

There are two general categories, or classes, of deworming products on the market:

  1. Benzimidazoles (oral dewormers). Oral dewormers interfere with the microtubules of the parasites, which depletes energy supply and causes parasite death. These short-acting products are very effective against adult worms and other internal parasites but have little residual killing power.

  2. Macrocyclic lactones. The active ingredients within these dewormers cause nerve paralysis of internal and external parasites. Macrocyclic lactones provide longer control of parasites compared to benzimidazoles. These dewormers are available in pour-on, injectable and extended-release formulations.

    • Pour-ons and injectables typically have a residual activity anywhere from days to a few weeks.

    • Extended-release dewormers control parasites for up to 150 days.

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“Oral dewormers and pour-ons are great for feedlots, where cattle are not going to pick up worms repetitively,” said David Shirbroun, DVM, Boehringer Ingelheim. “In stocker and cow-calf herds that have long grazing periods, an extended-release dewormer that lasts up to 150 days can make a lot of sense for producers.

“Young animals are the most susceptible to parasites and will likely see the largest return on investment from long-duration parasite control,” continued Dr. Shirbroun. “To achieve the same efficacy as an extended-release dewormer, you would need to give about three treatments of a conventional pour-on dewormer over the course of the grazing season.”

The science behind extended-release dewormers

So, what makes extended-release dewormers last all season long? Here’s how the technology works:  

  1. After the initial subcutaneous injection, the drug concentration reaches a high peak to control parasites right away.

  2. Extended-release technology enables the remaining drug concentration to encapsulate into a gel matrix. This matrix continues to release the dewormer above therapeutic levels in the animal.

  3. The matrix breaks down approximately 70 to 100 days after the initial treatment and releases a second peak. After 150 days, the drug is eliminated from the body.

“There have been concerns that an extended-release dewormer could create parasite resistance faster than a standard dewormer,” noted Dr. Shirbroun. “However, the active ingredient is removed from the body in much the same way as current pour-on and injectable dewormers on the market. It doesn’t go below therapeutic levels during its slow-release phase, which is what can lead to a quicker onset of parasite resistance.”

To manage resistance, Dr. Shirbroun recommends talking to your veterinarian about refugia. Refugia (in which a percentage of the herd is selectively not dewormed) is recognized as one of the most important factors in delaying the onset of parasite resistance. Leaving a portion of the parasite population in “refuge” from dewormers reduces the drug-resistance selection pressure caused by the dewormer. 

Putting extended-release deworming to the test 

Rob Gill, manager of eight, cow-calf operations and an 11,000-head feedlot located throughout Wyoming and surrounding states, decided to put an extended-duration dewormer to the test.

“We treated one group of heifers with just a drench and pour-on, and the other group received an extended-duration dewormer,” he said. “Heifers that received the longer-acting dewormer were about 32 pounds heavier coming off grass in the fall.”   

Gill said that while producers may be hesitant about the initial investment of a longer acting dewormer, there's a significant payoff between the lower stress levels and added weight gain.

“We treat cattle before they go out to pasture, and we don’t have to touch them again until they’re in the feedlot,” he added. “The dewormer is worth our investment because it keeps parasites out of pastures, resulting in better weight gain that carries through to feedlot performance.” 


Three tips for any deworming product and program 

No matter the type of product you choose, David Shirbroun, DVM, Boehringer Ingelheim, recommends adhering to the following practices to get the most out of your dewormers: 

1. Use diagnostics to evaluate parasite populations and product efficacy. A fecal egg count reduction test,or FECRT, is a standardized diagnostic tool that can evaluate the efficacy of your deworming products. Typically, a 90% or greater reduction in the fecal egg count indicates that your dewormer is performing the way it’s supposed to. A coproculture can help find the species of parasites most prevalent within the herd, so you can implement a targeted approach to parasite control. 

2. Read the product label closely to be sure it offers the protection your herd needs. Each class of dewormers has its own strengths and weaknesses, and certain classes are more effective against specific parasites. By performing regular diagnostic testing and paying close attention to product labels, you can determine how effective each dewormer will be at controlling the key parasites in your herd. 

It’s also difficult for the dewormer to do its job if not administered correctly. Read the label to be certain the product is stored correctly, the dose you’re administering is accurate for the weight of the animal you’re treating, and your equipment is properly functioning prior to treating the animals. 

3. Work with your veterinarian. Every producer’s situation is unique; no two herds are the same, and neither are their parasite burdens. That’s why consulting your veterinarian is so important. They can help evaluate your operation’s needs and recommend a deworming protocol and product(s) based on the findings. Your grazing season period, the age and class of your animals and the grazing history of the pasture are all considerations to discuss. 

LONGRANGE IMPORTANT SAFETY INFORMATION: Do not treat within 48 days of slaughter. Not for use in female dairy cattle 20 months of age or older, including dry dairy cows, or in veal calves. Post-injection site damage (e.g., granulomas, necrosis) can occur. These reactions have disappeared without treatment. Not for use in breeding bulls, or in calves less than 3 months of age. Not for use in cattle managed in feedlots or under intensive rotational grazing.



1 Rademacher RD, Behlke EJ, Parr SL, et al. An evaluation of eprinomectin extended-release injectable (LONGRANGE) on the performance of yearling cattle on pasture in western Canada. Bov Pract 2018;52(1):46–52.

2 Andresen CE, Loy DD, Brick TA, Gunn PJ. Case study: Effects of extended-release eprinomectin on cow-calf performance and reproductive success in a fall-calving beef herd. Prof Anim Sci2018;34(2):223–229.

LongRange® is a registered trademark of Boehringer Ingelheim Animal Health USA Inc. ©2022 Boehringer Ingelheim Animal Health USA Inc., Duluth, GA. All Rights Reserved. US-BOV-0046-2022-A

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