Recommendations
- Use dewormers wisely. Checking manure (fecal egg counts) helps you treat only animals that need it, keeping dewormers working longer and protecting the environment.
- If you use endectocides (combined internal and external dewormers), keep cattle in a dry lot or pen for a short time after treatment to help protect dung beetles on pasture.
- To control flies, apply insecticides directly (ear tags, backrubbers, sprays, or dusts) instead of feed-through products to reduce impact on aquatic species and pollinators.
Balancing environmental and animal health
Successful parasite management balances the health of the herd, the health of the environment, and the costs of treatment and production losses.
Creating a strategy with your veterinarian for responsible and evidence-driven parasite control is the first step in using dewormers intelligently and strategically. Before selecting a dewormer, decide which livestock to keep in the herd, which to cull, which to monitor using fecal egg counts (FEC), and which to deworm.
Dewormers and insecticides can have unwanted effects on the environment: some contaminate water and harm aquatic species, and others impact pollinators or other beneficial insects through livestock waste. The environmental effects of dewormers and insecticides in grazing livestock are not yet fully known.
The following is a review of best practices for reducing the environmental impact of parasite treatments in grazing cattle. These practices can be considered along with animal health and cost considerations when developing a parasite control plan.
Environmental impacts of livestock parasite management
There are three main parasite control methods discussed here: oral dewormers, endectocides, and insecticides. The routes by which they are given and are excreted by the animal determine how the product will impact the environment.
- Oral dewormers act on internal parasites.
- Endectocides control both internal (roundworms) and external (flies, ticks) parasites. They enter the environment through livestock manure.
- These dewormers kill insects that live in and eat manure, such as dung beetles, which naturally help control flies.
- External insecticides, like pyrethroids and organophosphates, enter the environment through livestock urine. This can impact aquatic species. They also last for extended periods on livestock hides and have unintended effects on pollinators.
The products’ impacts on pollinators, aquatic species, and other beneficial insects depend on the dose, how often they are used, the region of the country, and the season.
Dewormer effects on soil health
There are fewer studies investigating the impact of dewormers on soil health than on pesticides and antibiotics. However, dung beetles, various insects, and earthworms improve soil health by bringing nutrients from the manure to the soil. Dewormers may reduce dung beetle and earthworm activity. This slows the decomposition of manure, which reduces the cycling of nutrients into the soil.
Microorganisms are important to soil health because they also help to cycle nutrients. Albendazole has been found to reduce the amount of microorganisms like fungi and archaea in soil. Albendazole, ivermectin and eprinomectin may reduce nitrogen cycling in the soil.
These impacts on soil health depend on the dose, how often they are used, the region you live in, and the season of the year.
Active ingredients
Review the product label for the active ingredient of each dewormer, endectocide or insecticide you use. The active ingredients will be listed in parentheses or near the commercial product name for dewormers, or in the ingredients list by percentage for insecticides.
The following table of recommendations was developed as guidance to producers before turning cattle out on public lands, but applies to any producer who would like to fine-tune their parasite control program with environmental impacts on their pastures in mind.
If the product is a combination product, with multiple ingredients, follow the recommendation for the active ingredient with the longest timeline.
| Active ingredient | Type | Dung beetle toxicity | Impact on aquatic species or pollinators | Best management practice |
|---|---|---|---|---|
| Abamectin | Endectocide (internal and external) | High | Low | Wait 2 months after treating and before turning cattle out on pasture. |
| Fenbendazole, oxfendazole, albendazole | Oral dewormer | Low | Low | Good choice during dung beetle active seasons; no wait before turning cattle out onto pasture. |
| Insect growth regulators (diflubenzuron / ClariFly) | Insecticide (feed-through) | Moderate | Low | No effects on adults, but possible risk to development of dung beetle larvae. |
| Ivermectin, doramectrin, eprinomectin (except LongRange) | Endectocide (internal and external) | Moderate to High | Low | Wait 1 month after treating and before turning cattle out on pasture. |
| LongRange (eprinomectin) | Endectocide (internal and external) | High (extended release prolongs excretion window) | Low | Significant potential for dung beetle toxicity due to long shedding time in environment. Wait longer than 2 months after treating and before turning cattle out on pasture. |
| Moxidectin | Endectocide (internal and external) | Moderate | Low | Wait 2 weeks after treating and before turning cattle out on pasture. |
| Organophosphates, carbamates | Insecticide (topical or ear tags) | Low | Low | Vary greatly in toxicity, residue levels, and excretion, but in general produce little environmental residue. |
| Permethrins, cypermethrins (except Ultra Boss) | Insecticide (topical or ear tags) | Low | Moderate | Wait 2 weeks after treating and before turning cattle out on pasture. |
| Ultra Boss (permethrin) | Insecticide (topical) | Low | High | Significant potential for aquatic species/pollinator toxicity due to long shedding time in environment. Wait 2 months after treating and before turning cattle out on pasture. |
Product class
- White dewormers or benzimidazoles (e.g., fenbendazole/SafeGuard): Oral products with action against internal parasites. They are generally less toxic to dung beetles and soil macrofauna than macrocyclic lactones, making them a preferred alternative for preserving dung insects.
- Macrocyclic lactones (e.g., ivermectin, eprinomectin/Eprinex): Commonly used against internal and external parasites, but residues excreted in manure can cause death or developmental disruption in dung beetle larvae and soil nematodes. Ivermectin (Ivomec) or eprinomectin (Eprinex) are safer for dung beetles than doramectin (Dectomax). Long-acting formulations are excreted into the environment for a longer time.
- Insect growth regulators (e.g., diflubenzuron/ClariFly): Disrupt insect development. While safer for adult beetles and vertebrates, residues in manure can impair larval development of dung-attracted insects.
- Permethrins and cypermethrins (e.g., CyLence): Deter insects such as flies via topical sprays, dips, or ear tags. Rapidly excreted in urine; residues on animals can directly affect aquatic species and pollinators. Products delivered via ear tag are less toxic than topical pour-ons or sprays of the same ingredients.
Reviewed in 2026