For decades, the standard response to summer parasites was simple: run the herd through the chute and apply a single dewormer to every animal. But according to veterinary experts, that ‘blanket’ approach is now a contributing driver of a growing crisis: anthelmintic resistance.
As internal parasites evolve to survive common treatments, producers must shift from generic schedules to data-driven, veterinarian-guided protocols to protect their herd’s health and their operation’s profitability.
Dr. Julia Herman, National Cattlemen’s Beef Association (NCBA) beef cattle specialist veterinarian, says parasite management does vary by region with differences in climate, environmental conditions, host susceptibility and farm/ranch management practices.
“Rotating pastures strategically can optimize nutrition and pasture use, but parasite management is variable depending on stocking density, age of cattle, time of year recent rainfall – lots of factors are hard to predict,” she explains. “What does not vary by region is anthelmintic resistance, where internal and external parasites have developed resistance to the animal health products and dewormers readily available for parasite control.”
What is Anthelmintic Resistance in Cattle?
Anthelmintic resistance has been recognized in small ruminants for many years, but the beef industry is not immune. She explains resistance in intestinal worms of cattle has been documented for more than 20 years.
John Gilliam, Oklahoma State University associate professor and clinical veterinarian, stresses the beef cattle industry needs to recognize that anthelmintic resistance is present and is becoming more of a concern. Anthelmintic resistance has been documented in multiple parts of the U.S., not just the Southeast region.
Common Mistakes in Parasite Management
Promotion of resistance comes from misuse of the products available. Herman says there are a few common ways that misuse could occur:
- When groups of animals are dosed to the average weight of the group, the heavier animals are likely underdosed, meaning worms are not completely killed and resistant worms have a higher chance of surviving.
- Certain products, like pour-on dewormers, may increase resistance more than other products due to underdosing or inappropriate application. This includes not applying along the back from head to tail. “Squirting cattle with dewormer as they run by is a great way to waste product, waste money and increase anthelmintic resistance,” Herman says.
- Using anthelmintic products for parasites not on the label, such as using a dewormer for flies. “The Environmental Protection Agency has specific labels and regulations for each topical anthelmintic,” Herman explains. “Be sure to read the label of each product, use it for its intended parasite, and follow withdrawal times.”
Preventing resistance in the animal health realm can apply to both antimicrobial and antiparasitic products. Because of anthelmintic resistance, treatment protocols have become more complex than giving a single product and necessitate veterinary consultation.
“As discussed in the Beef Checkoff-funded Beef Quality Assurance (BQA) Program, proper dosing to body weight of the animal plays a role in effectiveness of the medication,” she explains. “While much focus is placed on withdrawal times for antibiotics, do not forget that many topical and injectable parasite treatments have withdrawal periods to adhere to.”
Beyond anthelmintics, which can be very effective when used properly, alternative methods to managing internal parasites can be effective adjunct strategies.
Herman also stresses the fact of not blanket-treating the entire herd.
“Unless there is a diagnosed problem, blanket treatment is not recommended,” she says. “Working with a veterinarian or extension specialist is crucial to understanding the herd’s parasite risk. A new school of thought that favors treating a small percentage of the herd or only unthrifty animals rather than treating every animal in the herd. Preserving susceptible worms through refugia programs is a technique that many herds are implementing.”
How to Perform a FECRT
To effectively treat or control parasites in the herd, it is important to know exactly which ones are a problem. This can be challenging at times, so it is critical to have a resource team ready to assist.
“Working with your local veterinarian and extension agent will help tailor a strategy to the specific operation, using multiple modalities to protect your herd,” Herman says. “Coordinating with neighboring ranches on parasite control would also improve overall success of the program.”
Every producer has a parasite control program but may not be assessing the efficacy of their program. Gilliam reminds producers there is no way to know if your herd has resistance without looking for it.
This is where the Fecal Egg Count Reduction Tests (FECRT) can play a key role. These tests can be run as a screening test with the help of your veterinarian and are designed to measure the efficacy of the anthelmintic treatment.
The FECRT requires a sampling of a group of animals at the time of treatment followed by a second sampling 10 to 14 days after treatment. This test can be used for any oral, injectable or pour-on anthelmintic products.
“Labor and cost will need to be evaluated for each operation since cattle will need to be handled at least twice for sample collection and potential treatment,” Herman says. “Testing around 20 randomly selected animals within the herd has been shown to be a representative sample for detecting resistance at the herd level. If a herd has less than 20 animals, all of them would need to be tested.”
Another way to monitor, Gilliam adds, is completing routine surveillance of fecal samples, which can be a strategy to count the number of parasite eggs to see if deworming is needed for an individual animal.
Different diagnostic laboratories, technical services companies and veterinary clinics will use different tests for determining fecal egg counts, so it is important to plan ahead and have that conversation before collecting samples.
Some laboratories will accept composite sampling, which means combining multiple samples into one sample in a standardized manner, which can save on costs.
“Parasite control programs, whether completing surveillance or treatment, can be complicated to develop so working with your herd veterinarian is vital,” Herman summarizes.
Parasite prevention programs are an essential part to the herd health plan and should be re-evaluated on an annual basis. The significance of considering the cattle’s entire environment — from optimizing nutrition, having a solid herd health program, using low-stress handling to provide the foundation for a strong immune system and healthy cattle — cannot be emphasized enough.
She reminds producers reviewing the BQA principles will help cattle producers focus on these preventive practices that will improve animal health, optimize productivity and reduce management costs.
Your Next Reads:
