Kill more parasites, avoid resistance with combination treatment

As scientists continue to look for new parasiticides, the cat­tle industry must seek ways to preserve the efficacy of current and future deworming products on the market.

One solution is using two dewormers from different drug classes. This practice is known as combination treatment and has been proven to reduce fecal egg counts in cattle herds by nearly 99%. When high efficacy like this is achieved, there are also few­er resistant parasite survivors to cause trouble down the road.

How does combination treatment work? All commercially available dewormers kill parasites. Where they differ is the spec­trum of parasites covered as well as their duration.

There are two classes of cattle dewormers, depending on their chemical structure. Successful combination treatment uses two dewormers from different classes with different modes of action:

1. Macrocyclic lactones (endectocides) come in both injectable and pour-on forms. The active ingredients cause nerve paraly­sis of both internal and external parasites. This class provides longer-duration control compared to benzimidazoles.

2. Benzimidazoles (white dewormers) are administered orally and act as purge dewormers to internal parasites. They inter­fere with microtubules of the parasites, depleting their energy supply and eventually causing their death. Benzimidazoles are usually in and out of the system within a couple of days.

It’s important to remember that there are multiple active ingre­dients within each class, all of which use the same mode of action to eliminate parasites.

If you’re looking to boost cattle performance and productivity, combination treatment can be a great option. By administering a parasiticide from both classes at the same time, you maxi­mize efficacy and control more parasites—reducing the risk of developing resistance in your herd. However, this practice is not something to try without a conversation with your veterinarian.

In addition to combination treatment, there are other ways cattle producers can maximize dewormer effectiveness:

Product selection — While active ingredients may be the same, there can be differences in how dewormers are made, the quality measures taken and even other ingredients included. As a result, some generic products perform quite differently. Be sure to choose products backed by extensive research.

Product application — It’s difficult to know for sure if the deworming product is doing its job if not administered correctly. Be certain the product is stored correctly, the dose you’re admin­istering is accurate for the weight of the animal and that your equipment is properly functioning. A frequent practice is to dose dewormers according to the average weight of the herd. While convenient, this can overdose or under-dose a number of cattle and diminish the drug’s effectiveness. Investing in a cattle scale will help with accurate dosing and reduce product waste.

Diagnostic testing — Performing routine diagnostic tests such as fecal egg counts and coprocultures can help you assess the effectiveness of your deworming program and determine which species of parasite(s) is infecting the cattle. Your herd veterinarian can advise you on the proper method and assist you with con­ducting these tests for the most accurate results.

Refugia — This practice, which means a percentage of the herd is intentionally not dewormed, is recognized as the single most important factor in delaying parasite resistance. Leaving a portion of the parasite population in “refuge” from dewormers reduces drug-resistance selection pressure.

Pasture management — Limit overgrazing, maintain appro­priate forage height and rotate pastures if possible.

Cattle management — Producers can increase overall herd immunity through routine vaccinations and enhanced nutrition. In addition, implementing biosecurity measures can help prevent the introduction of resistant parasites.

Veterinarian involvement — Correct dosing, choosing the right animals to deworm and monitoring parasites will benefit your cattle herd and the future of the industry. No two herds or opera­tions are the same, and neither are their parasite burdens. Your vet­erinarian can help evaluate your operation’s needs and recommend deworming programs and products based on the findings. Your operation type, pasture history and grazing season, along with age and category of your animals, will all be considerations.

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