Internal parasites can dramatically alter how an animal’s immune system functions, weakening its ability to respond to preventive health protocols like vaccinations. Effective and sustainable parasite management is essential for maintaining animal health and boosting the overall performance of your herd.
However, sustainable deworming is not just about treating parasites – it’s about managing resistance and preserving the efficacy of deworming products for as long as possible.
Sustainable deworming has four pillars to make it truly effective, including diagnostics, combination treatment, refugia and pasture management. These strategies aim to control parasites while maintaining the effectiveness of current deworming products available in the U.S., ensuring healthy cattle and profitable operations for years to come.
1. Diagnostics
Partnering with your veterinarian to perform diagnostics can help you better understand which parasites are impacting your cattle and whether parasite resistance is a potential concern. There are three types of diagnostic testing for deworming programs:
- Fecal egg count (FEC): Collected manure samples are tested to count the number of eggs per gram in each sample. While this test doesn't identify species, it helps categorize parasites for targeted control.
- Coproculture: Eggs from manure samples are hatched in a laboratory. Once parasites reach the first larval stage (L1), they have unique characteristics that distinguish one species from another. This information is important because cattle at different ages and phases of production can be infested with different species of parasites. Coproculture tests help focus parasite control programs and identify the most effective deworming program for your herd.
- Fecal egg count reduction test (FECRT): Manure samples are collected at the time of deworming, and both FEC and coproculture tests are performed. A second set of samples is collected at a specific time period from the same animals post-deworming. The class of dewormer will determine how many days after treatment samples should be collected. FEC and coproculture tests are performed on the second samples, and compared to the results from the first samples. These tests show the reduction in fecal egg count related to a specific species. A greater than 90% reduction in fecal egg count indicates your deworming program is working effectively.
Running diagnostics is extremely valuable to better understand the effectiveness of a deworming program. The biggest barrier for many farmers is the time and labor involved in collecting samples for the diagnostic test. However, the results are often worth the extra effort.
2. Combination treatment
Repeatedly using the same deworming product can open the door for more parasites to survive. Using two or more dewormers from different drug classes with different mechanisms of action, known as combination treatment, can target parasites from different angles and may reduce the amount of parasite survivors.
All commercially available dewormers control parasites. Where they differ is the spectrum of parasites covered, as well as the duration of their control. Commonly used cattle dewormers belong to three classes: macrocyclic lactones, benzimidazoles and imidazothiazoles.
It’s important to remember that there are multiple active ingredients within each class, and those active ingredients have the same mode of action to eliminate parasites.
3. Refugia
Refugia refers to leaving a percentage of the herd untreated, with the goal to keep part of the parasite population susceptible to dewormers.
Refugia isn’t a new concept and is practiced in many other areas of agriculture, including crop production. In terms of internal parasites, refugia allows untreated animals to pass on the parasites with genes susceptible to the dewormers.
Refugia dilutes the dewormer and results in both susceptible and potentially resistant parasites in the environment. When animals pick up the parasites, they will likely have some that are susceptible and some that are potentially resistant, so your deworming program will still have a benefit against those susceptible parasites.
The percentage of your herd to leave untreated varies, based on the efficacy of the deworming program. Diagnostics are important to help understand efficacy and to implement a successful refugia program.
4. Pasture management
Effective pasture management plays a crucial role in minimizing cattle exposure to parasites. It’s important to reduce parasite loads in pastures and limit the number of parasite larvae ingested by cattle.
Avoid overgrazing, as most infective larvae are found in the bottom 2 inches of pasture. Overgrazing increases the likelihood of cattle ingesting larvae because they’re grazing forages closer to the ground. Rotating pastures and managing stocking density help reduce overgrazing and give pastures a rest.
In this situation, noxious plants can also pose less of a threat because palatable forages are still available since the pasture hasn’t been overgrazed.
Pasture management is especially important during times of drought, when the available feedstuffs are already diminished. You want all available feedstuffs to go to the animal and not the parasite. While weather can be unpredictable, some farmers and ranchers will prepare for drought situations by maintaining extra capacity to account for diminished forage availability during drought.
When rotating pastures, avoid grazing the same pastures in the fall of one year and the spring of the next. Infective parasite larvae from eggs deposited in manure in fall may survive the winter on the pasture and be a source of pasture contamination for cattle grazing in the spring.
By working with your veterinarian to incorporate the four pillars of sustainable deworming – diagnostics, combination treatment, refugia and pasture management – you can effectively manage internal parasites, support cattle health and extend the efficacy of deworming products. This approach not only protects the health of the herd but also ensures the long-term success and sustainability of your operation.
References omitted but are available upon request by sending an email to the editor.
