Pour it On: Topical Cattle Parasite Control


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Topical parasite control products remain a popular and effective choice for cattle producers.

Parasite control might be one of the only processing steps most producers agree on. The equation is simple: fewer parasites result in more gain and better condition. Today, producers have a wide array of delivery options for delivering products to their cattle. Yet, pour-ons remain a popular option – and for a good reason.

Lice control

Pour-on dewormers have an advantage in lice control, said Eric Moore, DVM, director of Technical Services – North America for Norbrook Laboratories Ltd.

Two types of lice infest cattle: biting lice and sucking lice. Biting lice feed on dead skin cells, hair, and oil secretions. Sucking lice feed on blood. With injectable dewormers, the active ingredient may only be delivered to sucking lice.

“With injectables, only the lice that feed on blood are controlled,” Moore said. “That means there are whole groups of lice you don’t get, which can leave a hole in your protection.”

Lice aren’t just a nuisance to cattle. Increased rubbing and scratching activity can result in damage to fences and structures. Plus, the cattle are devoting energy to scratching when they should be eating and gaining, he said.

Administration basics

Injectable parasite control products have a more assured delivery. However, pour-on products can be just as effective – as long as the product’s dose and delivery are correct.

“With an injectable, you know you’re getting the dose in the system,” Moore said. “With a pour-on, it can be variable by hair coat.”

To get the best result, producers should apply the right dose of the product. An accurate weight is key to avoiding under-dosing, he advises. (See sidebar for more application tips.)

Pour-on dewormers can complement a complete processing program by eliminating an injection site and reducing labor.

“Pour-ons are convenient,” Moore said. “It’s something people really need if they have limited labor or limited facilities. Just get a good dewormer into them, and you have less risk of being injured or anything like that. It’s great for people working cattle in an old alleyway or for cattle too big to get into the chute. Even with other options – like flakes or blocks – you’re not getting external parasite control.”

Feeding cattle representative of Topical Cattle Parasite Control.

Timing it right

In the fall, cattle can experience increased lice pressure. Dewormers can sometimes fail to control lice without proper timing and application, Moore said.

Lice populations often increase during the winter months due to the animal’s hair coat providing additional insulation from cold temperatures. For that reason, warmer temperatures in the spring usually result in reduced numbers of lice.

Treating too early in the fall may provide an opening for lice numbers to rebound as temperatures fall, South Dakota State University Extension advises.1

Putting pour-ons in the rotation

Moore said that producers who rely on pour-on dewormers as part of a rotational deworming strategy should understand the active ingredients in each product.

“Be cautious when you go by label indications,” he said. “Producers may think they are using two different products, but they both might be in the macrocyclic lactone class.”

Pour-on dewormers can be worked into a year-round parasite control plan, and deworming should always be considered before grouping cattle together, Moore advised.

“When I have actual feed costs, get the cattle cleaned up before you put them in places together,” he said. “Deworming actually improves feed efficiency by 9% or 10%. That makes investing in a good dewormer a good value. The other school of thought is to deworm cattle before they go out on grass to make sure you’re not seeding pastures with parasites.”

The ease of use of pour-on dewormers can also lead to frequent use, which isn’t always a good thing, Moore said.

“Any time you use a product a lot, you select for parasites that are resistant to the active ingredient. No product is 100% effective. So, you end up selecting for the ends of the bell-shaped curve that aren’t susceptible to the product. That’s always something to think about,” Moore said. “Pour-ons have a valuable place in the industry. They are convenient to use, but they need to be applied correctly and dosed correctly.”

1 Rusche W. Winter Lice Control. SDSU Extension. June 10, 2020. Accessed Feb. 18, 2021. Available at: extension.sdstate.edu/winter-lice-control.

2 Boxler D. Cattle Lice. UNL Beef. January 2017. Accessed Feb. 18, 2021. Available at: beef.unl.edu/cattle-lice.

5 Steps for optimal pour-on administration:

  • Calculate accurate dosing based on weight
  • Treat every animal
  • Clean dirt and debris from the coat before application
  • Apply along the top line in a narrow strip extending from the withers to the tail head
  • Follow label directions for re-treatment windows