Drench resistance in cattle & how to avoid

There are two words no cattle producer wants to hear: drench resistance.

This is a growing challenge across Australia, as some producers notice their usual treatments are becoming less effective against internal and external parasites like worms, flukes, and cattle tick. Each week, we receive calls asking the all-important question: ‘How can I prevent pour-on drench resistance in my cattle?’

There are a few parts to this, and we’re here to help guide you through them. Keep reading for our expert tips for avoiding cattle drench resistance.

What causes drench resistance?

Drench resistance is caused by random genetic mutations in worms that are rare but transmissible from parent to offspring. When drenches are used to wipe out worms, the resistant ones survive and reproduce, passing on their tolerance. This creates a population of worms that no longer responds to that particular drench or active, which is when producers will start to experience pest control issues.

In Australia, resistance to the macrocyclic lactone (ML) group of drenches – which includes ivermectin, abamectin, doramectin, endomectin, and moxidectin – is becoming more prevalent. These drenches were game-changers when first introduced in the 1980s, offering long-lasting, broad-spectrum control, however overuse and under-rotation have allowed parasites to adapt over time.

Worm resistance vs drench resistance

It’s easy to confuse worm resistance and drench resistance. Here’s the difference:

Worm and parasite resistance is the animal’s ability to resist worm burdens. Think of this as your cattle’s immune system naturally doing its job – or, if worm resistance is low, not doing its job.

Drench resistance is when the parasites themselves become immune to the chemical treatment being applied. It develops over time as drenches are overused or underdosing to save costs occurs.

How often should you drench cattle?

There’s no right answer to how frequently you should drench your cattle for optimal pest control – rather, drenching frequency will depend on these factors:

The age and class of cattle (weaners vs yearlings vs breeders)
Location in Australia
Seasonal conditions (especially rainfall and temperature)
The parasite lifecycle and burden at the time

As an example, calves and young cattle are typically more susceptible to parasites and may require more frequent treatment.

In addition to these factors, the NSW Department of Primary Industries recommends tailoring your drenching program to consider local worm egg count data, paddock history, and your management systems.

The team at Specialist Sales can help you to interpret these variables and find a drenching plan that will suit your circumstances.

How long does a drench last?

The longevity of your cattle drench will depend on the chosen active ingredient, the formulation (pour-on, injectable, oral), and the environmental conditions in your area.

A high-quality macrocyclic lactone-based pour-on may offer several weeks of protection, while others may wear off more quickly under heavy rain or intense parasite pressure.

Long-acting injections offer a minimum of 51 days for cattle tick, but provide protection for certain worms up to 120 days. Many tick inhibitors offer up to 12 weeks of protection against cattle tick.

To ensure you’re administering cattle drench treatments at the appropriate intervals to keep your herd safe, monitor animal health closely and conduct periodic faecal egg counts. This will help you determine when re-treatment is needed.

How to avoid drench resistance in cattle

Avoiding resistance isn’t about drenching more – it’s about drenching smarter. Implement these tips from the experts at Specialist Sales to improve the efficacy of your drench:

Rotate ingredients: Avoiding repeated use of the same chemical group (e.g., MLs) – not just the exact product – is critical to sidestepping resistance.

Quarantine new cattle: By keeping new cattle separate from the rest of your herd, you’ll lower the chance of resistant worms from entering your property.

Use effective doses: Always follow the instructions found on your chosen product’s label to ensure you’re not over- or underdosing, as this will accelerate resistance.

Time your drenching strategically: Aim to align treatments with high-risk periods, such as post-weaning.

Combine actives: Combination drenches, especially oral triple-active drenches, will target worm-resistant populations more effectively than single-active drenches.

Monitor effectiveness: Pay close attention to the results of your drenching and conduct the necessary tests (e.g., faecal egg counts) to manage efficacy.

Choosing the right drench for Australian conditions

There’s no shortage of drenches available on the Australian market, but to achieve effective control, it’s important to know which types and active ingredients will suit your needs best.

1. Pour-on drenches

Pour-ons are convenient, rainfast, and widely used amongst Australian beef and dairy producers. They’re a good choice for treating both internal and external parasites, including lice, ticks, and buffalo fly.

Commonly used actives and products include:

Cydectin, Cattleguard, Neovemox (moxidectin): Known for its broad-spectrum control and long-lasting activity, moxidectin controls roundworms, lungworms, cattle ticks, buffalo flies, and lice. It’s dung beetle-friendly and rainfast, with nil milk and meat WHPs.
CattlePro, Ivomec, Imax CD, Ausmectin (ivermectin): Ivermectin-based products offer reliable coverage against internal and external parasites. The CattlePro range offers an ivermectin base in an affordable formulation, and has received excellent customer feedback and consistent results nationwide.
Cydectin Platinum (combination moxidectin-levamisole): Unlike ML drenches, this pour-on provides a combination of actives, including moxidectin and levamisole, with external parasite control and excellent efficacy against gastrointestinal worms. With a 7-day meat WHP, it’s ideal for resistance management in rotation.
Acatak Duo, TickPro Duo (combination fluazuron-ivermectin products): Products formulated with fluazuron, a long-term tick inhibitor, and ivermectin, which offers knockdown control against gastrointestinal worms and external parasites, are much less prone to resistance than ML drenches.
Avomec Plus (abamectin): A great option to add to your drench rotation, abamectin offers broad-spectrum coverage against external and internal parasites in cattle. Abamectin-based drenches are rainfast and have proven efficacy in the Australian market. Avomec Plus also contains triclabendazole to increase coverage.
Dectomax, Neovedor, Bovipour (doramectin): Doramectin is a highly active, ready-to-use, broad-spectrum drench that treats internal and external parasites.

2. Injectable drenches

Injectables can be a useful formula when cattle are under stress, or in wet weather when pour-ons may not hold. They often rely on the same active ingredients as their pour-on counterparts.

3. Oral drenches

Oral drenches are especially valuable in rotation strategies and often contain alternative or multiple active ingredients.

Fenbender, Panacur 100 (fenbendazole): Fenbendazole-based drenches are useful in combination rotations to protect against internal parasites.
Trifecta Triple Active Drench (combination levamisole-oxfendazole-abamectin): This powerful combination of actives puts up a strong fight against resistance.
Worma Oral Drench (oxfendazole): An economical option, Worma Drench is ideal for use across dairy and beef cattle to protect against roundworms and tapeworms.
WSD Levamisole Oral Drench (levamisole): WSD Levamisole Oral Drench effectively controls levamisole-sensitive gastrointestinal roundworms and lungworms, including those that are resistant to benzimidazoles.
Strategik Mini-Dose Worming Drench for Cattle (albendazole): This broad-spectrum anthelmintic oral white drench for cattle controls susceptible internal parasites like adult liver fluke, tapeworm, and lungworm in cattle.

Whether you’re managing a large-scale beef property or a small dairy herd, drenching is a critical component of ensuring cattle health. It must be done as part of a strategic parasite control program to ensure effectiveness, not just as a seasonal task.

Shop the full spectrum of cattle drenches now.

Need support making the best decisions for your herd, region, and budget? Get in touch with the Specialist Sales team today to receive expert advice.