Traditionally, when cattle were in the chute, every animal got a dose of dewormer. That approach may have worked in the past, but today, it’s leading to bigger challenges with parasite resistance. More and more producers are finding that treating the whole herd isn’t always the best answer — and that’s where refugia comes in.
Refugia Is About Doing More With Less
The concept of refugia is grounded in leaving a population of parasites unexposed to the dewormer treatment, which helps slow down the development of resistance. In practice, this is done by leaving select cattle untreated. While it seems counterintuitive, research has shown operations using refugia experience less resistance to the dewormers they use.
“A study in Georgia looked at 12 cow-calf operations and saw resistance in 11 out of the 12 operations,” explains Dr. Jody Wade, DVM, Boehringer Ingelheim. “The only farm that didn’t experience resistance was a farm that was incorporating refugia into their deworming program.”
For Oklahoma cow-calf producer Buck Rich, the strategy works, and it saves time and money in the process. “We hear more stories about parasite resistance and know if we’re not proactive about managing it, we’re going to compound our problem,” he said. “We’ve held back some cows from treatment and haven’t seen a drop in performance. If the cows don’t need it, we’re not going to waste the time or product.”
Running 2,000 pairs on his operation, Leaning Oak Ranch in Okemah, Okla., Rich works closely with his veterinarian, Dr. Tyler Thomas, a mixed animal practitioner and owner of Prague Veterinary Clinic in Prague, Okla., to build and maintain his deworming protocol.
“There’s been times when I would call Dr. Thomas and say, ‘Hey, this cow doesn’t look good,’” Rich remarks. “His response is often ‘Let’s wait to deworm.’ That can be hard to do, because you think you’re doing good by treating, but sometimes you’re not.”
While Thomas strongly supports refugia, he points out how easily the practice is misunderstood.
“Refugia can be perceived as doing nothing, but in reality, there’s a lot of strategy behind it,” he shared. “By leaving select animals untreated, we can maintain a population of susceptible parasites, dilute the resistant ones, and prolong the efficacy of our products.”
Where Refugia Works Best in the Herd
High-performing animals are often less burdened by parasitic loads and are less likely to require treatment, while underperforming cattle are those that need evaluation and potential treatment. By combining visual observation with strategic diagnostic testing, producers can better identify which animals should be treated and which can be safely left out, allowing refugia to work as intended.
“When we start to see inferior animals falling through the cracks, that is not the time to deworm the entire herd,” stresses Thomas. “If 20% of your cows are looking rough, spot-treat those cows. I would also record that information, and take that into account whenever you’re keeping breeding stock.”
For operations in the South, deworming for liver flukes in particular is not only common but is also one of the only ways to control the unique parasite. There are only a few products on the market that effectively kill liver flukes, making it a priority to protect products from resistance.
“We see the most damage from liver flukes in our cow herd, which is our main concern,” Rich says. “We’ve seen the benefits of killing flukes off every fall and plan to use our go-to flukicide — Ivomec Plus (ivermectin and clorsulon) — again this year.”
Practices like refugia are key to ensuring dewormers, including flukicides, remain effective for years to come.
Refugia Doesn’t Work Alone
Refugia works best when more than one deworming product is used within a protocol, which is also known as combination treatment.
“Using the same product over and over again can open the door for more parasites to survive,” Wade notes. “By administering dewormers from different classes, you target parasites in different ways, reducing the risk of developing parasite resistance in your herd.”
Dewormers fall into three main classes, each with a different chemical structure, mode of action and parasite coverage (Figure 1): macrocyclic lactones (endectocides), benzimidazoles (white dewormers) and imidazothiazoles. Each class controls a distinct spectrum of parasites, and for a different amount of time.
Along with refugia and combination treatment, routine diagnostics and pasture management are the other two strategies crucial to building an effective, sustainable deworming protocol. Together, these four strategies reinforce each other, maximizing parasite control and herd health.
To further explore refugia and the deworming strategies prioritized by Rich and Thomas, visit DewormingLegends.com.
