All You Need to Know on Livestock Dewormers

What are livestock dewormers?

Livestock dewormers or wormers, also called anthelmintics, are medications used to treat and control internal parasites (worms) in animals like cattle, sheep, goats, pigs, and horses. These parasites include roundworms, tapeworms, flukes, and lungworms, which can significantly impact an animal's health, growth rate, reproductive performance, and even lead to death in severe cases.

Dewormers are essential tools in livestock management because parasites can reduce feed efficiency and cause diseases that ultimately hurt production.

Dewormers come in different formulations, such as pour-ons, injectables, pastes, drenches, or feed additives. They work by either paralyzing or killing the worms, which are then expelled from the animal's body. Proper use of dewormers not only improves animal health but also supports food safety and economic efficiency for farmers and ranchers.

What is the most effective ingredient in dewormer for cattle?

The effectiveness of a dewormer depends on the type of parasites present and the resistance levels in a particular herd, but ivermectin is one of the most widely used and effective active ingredients in cattle dewormers. Ivermectin belongs to a class of drugs called macrocyclic lactones, which are highly effective against a broad spectrum of internal and external parasites, including stomach worms, lungworms, and lice.

Other commonly used active ingredients include:

Fenbendazole (a benzimidazole) and moxidectin, which is similar to ivermectin but has a longer residual activity.

Levamisole and albendazole are also used in certain cases, particularly when rotating products to prevent parasite resistance.

In regions where resistance is a concern, fecal egg count reduction tests (FECRT) may be used to determine which ingredient is still effective on a specific farm.

What are the three types of livestock dewormers?

Livestock dewormers are generally categorized based on their chemical class, which reflects their mode of action. The three main classes used in cattle are Macrocyclic Lactones (MLs), Benzimidazoles and Imidazothiazoles.

• Macrocyclic Lactones (MLs): Includes ivermectin, doramectin, eprinomectin, and moxidectin. These are effective against both internal parasites (like gastrointestinal worms and lungworms) and some external parasites (like lice and mites). They are available as injectables and pour-ons.
• Benzimidazoles: Includes fenbendazole and albendazole. These are broad-spectrum dewormers typically administered orally (paste, drench, or feed additive). They are effective mainly against gastrointestinal parasites and some tapeworms.
• Imidazothiazoles and Tetrahydropyrimidines: Includes levamisole and morantel tartrate. These work well against nematodes (roundworms) and are often used in rotation to prevent resistance. Levamisole is often used as an injectable or drench.

Rotating between these classes helps reduce the risk of drug-resistant parasites.

How often should you deworm your livestock?

The frequency of deworming depends on several factors, including the type of livestock, age, climate, management system, and parasite load in the environment. For cattle, a general recommendation is to deworm at least twice a year, typically in the spring and fall.

Spring deworming targets parasites picked up over the winter, while fall deworming is important before wintering animals to reduce worm burdens going into colder months.

In intensive systems or high-parasite environments, more frequent deworming (every 3–4 months) might be necessary. However, it's becoming increasingly important to avoid overusing dewormers, as this can lead to anthelmintic resistance.

Fecal egg count tests can help determine parasite loads and whether deworming is necessary. Strategic deworming based on actual need is now the preferred approach.

What age do you worm calves?

Calves are typically dewormed starting at around 2 to 3 months of age, depending on environmental exposure and weaning practices. Young calves can pick up parasites shortly after birth, especially if they are grazing contaminated pastures.

A common practice is to deworm calves at weaning, which is usually around 6 to 8 months of age, as this is a stressful time when their immune systems may be compromised.

If calves are raised on pasture with a known parasite problem, deworming at 2–4 months, and again at weaning, may be warranted. Afterward, timing depends on fecal egg counts, pasture rotation, and overall herd management.

Which is better, a pour-on, paste, or injectable cattle dewormer?

The best dewormer delivery method depends on the target parasites, the environment, and ease of application. Here's a breakdown:

Injectables (like ivermectin or moxidectin) are often the most reliable in terms of internal parasite control, especially for lungworms and gastrointestinal worms. They deliver the drug systemically, ensuring it reaches internal organs.

Pour-ons are convenient and easy to administer, especially for large herds. However, their effectiveness can be reduced by weather (e.g., rain or sun) or if animals have dirty or oily coats. They're commonly used for both internal and external parasites (lice, mites, etc.), but they may not be as consistently effective against all internal worms.

Oral pastes or drenches can be very effective, particularly fenbendazole-based products. They require proper dosing and handling but have excellent efficacy when administered correctly.

Ultimately, injectables tend to be the most effective, especially when targeting internal worms, but a strategic combination or rotation between types is often best to reduce resistance and cover different parasite species.

How to tell if your cows need worming?

Signs that your cattle may need deworming include:

• Poor body condition or weight loss despite adequate nutrition
• Rough or dull coat
• Diarrhea or soft manure
• Bottle jaw (swelling under the jaw, often from severe worm burdens)
• Coughing (could indicate lungworms)
• Reduced feed efficiency and slow growth
• Low weaning weights or poor reproductive performance

However, subclinical infestations (without obvious signs) can still impact productivity.

The most reliable method to determine if your cows need worming is through fecal egg count testing. This test involves collecting manure samples and having them examined under a microscope to count parasite eggs, helping guide deworming decisions and monitor resistance levels.

Can I deworm a pregnant cow?

Yes, you can deworm pregnant cows, but you must choose the product carefully. Many dewormers are labeled as safe for use during pregnancy, especially macrocyclic lactones like ivermectin and moxidectin, when used according to label directions. Fenbendazole is also considered safe during pregnancy and is commonly used.

However, some dewormers, like albendazole, are not recommended during early pregnancy because they may cause birth defects or interfere with embryo development. Always check the label and consult a veterinarian before deworming pregnant animals.

Strategic deworming before calving can help reduce the parasite burden in the cow and minimize transmission to the calf. It's typically done in the last trimester, ensuring the cow is in optimal condition for calving and lactation.

What are the best cattle dewormers or wormers?

Jeffers offers a wide range of options for cattle wormers for you to choose from. Here are our top product recommendations you can start with:

1. Noromectin Injectable Cattle & Swine Wormer (1% Ivermectin)

   Noromectin (ivermectin) Injection is an injectable parasiticide used for the treatment and control of internal and external parasites in cattle and swine. This broad-spectrum solution effectively targets parasites like gastrointestinal roundworms, lungworms, grubs, sucking lice, and mange mites, ensuring optimal health and productivity. Its convenience, safety, and low-volume dose make it a trusted choice for parasite control.

2. Injectable Ivermectin Cattle & Swine Dewormer

   Generic Ivermectin Dewormer (1% Ivermectin Injectable) Cattle and Swine Wormer for the treatment and control of gastrointestinal roundworms, lungworms, grubs, and ectoparasites, horn flies, sucking and biting lice and sarcoptic mange mites in cattle.

3. Valbazen Broad-Spectrum Oral Dewormer

   Valbazen Broad Spectrum Dewormer is an oral suspension for use in cattle, sheep, and goats for the removal and control of adult liver flukes, tapeworms, stomach worms, intestinal worms, and lungworms in cattle and sheep, and for adult liver flukes in nonlactating goats.

    

4. Safe-Guard 10% Suspension Cattle and Goat Dewormer

   Safe-Guard 10% Suspension Dewormer is a broad-spectrum fenbendazole-based dewormer for use in beef and dairy cattle, as well as goats. It helps remove and control key internal parasites, including lungworms, stomach worms, and intestinal worms.

5. Safe-Guard Multi-Species Medicated Dewormer Pellets

   Safe-Guard Multi-Species Dewormer is a versatile, broad-spectrum pelleted dewormer formulated with 0.5% fenbendazole to help control and eliminate a wide range of internal parasites in multiple species. With 2.27 grams of fenbendazole per pound, it's effective in beef and dairy cattle, horses, swine, goats, growing turkeys, and even zoo and wildlife animals. Ideal for integrated or mixed-animal operations, this easy-to-feed formula offers reliable parasite protection with no milk withdrawal for dairy animals and no slaughter withdrawal for swine.

6. Dectomax Injectable Wormer

   Contains 1% injectable solution for cattle and swine. An SQ or IM injectable wormer indicated for the treatment and control of internal and external parasites in cattle and swine, including 36 stages of adult parasites. Prevents infections for 28 days against the small intestinal worm and the lung worm and protects for 21 days against the brown stomach worm.

7. Ivomec Plus Injectable Cattle Wormer

   Only Ivomec Plus wormer kills more types of parasites in a single dose, including internal AND external parasites AND liver flukes. Administer 1 mL per 110 lb body weight SQ only.

    

8. Eprinex (eprinomectin) Pour-On Cattle Wormer

   Apply along back at 5 mL per 100 lb body weight. Measuring cap makes dosing quick, easy, and accurate.

9. Bimectin Pour-on Cattle Dewormer

   Contains 5 mg Ivermectin per mL. For Cattle (Not for use for female dairy cattle of breeding age). Bimectin Pour-on is used to aid in control of gastrointestinal roundworms, lungworms, grubs, horn flies, sarcoptic mange mites, sucking and biting lice.

10. Synanthic Bovine Dewormer Suspension, 22.5%

    Contains oxfendazole. Not cleared for female dairy cattle of breeding age. Give orally at the rate of 1 mL per 110 lbs of body weight. Aids in control of lungworms, brown stomach worms, barpole worms, bankrupt worms, threadneck intestinal worms, coopers worms, hook worms, tapeworms, and nodular worms.