Deworming Sheep: A Complete Guide

Deworming sheep – no matter how new you are to raising this kind of livestock, it’s important that you understand the ins and outs of this process. Deworming sheep isn’t complicated, but since sheep are so vulnerable to internal parasites, it’s important to know all the steps involved in preventing them.

What Parasites Are Common in Sheep?

What Parasites Are Common In Sheep

Although any kind of livestock can suffer from internal parasites, sheep and goats are some of the most susceptible to serious illness and death. They can quickly lose weight and suffer other symptoms like lethargy and diarrhea if they have heavy fecal egg counts.

Because of this, it’s important to be aware of the most common internal parasites of sheep as well as the best methods to prevent and remove them.

Gastrointestinal worms include things such as roundworms, stomach worms, and nematodes. Among these, the most dangerous parasite is the barber pole worm. This species is a blood-sucking organism that feeds upon the lining of the sheep’s “true” stomach and causes serious anemia.

This is the internal parasite responsible for a condition known as bottle jaw, in which a swelling of fluid appears beneath the jaw. It is incredibly difficult to control.

Other types of internal parasites of sheep include tapeworms, lungworms, liver flukes, and meningeal worms, though all of these are far less common than gastrointestinal worms.

What Are the Symptoms of Worms in Sheep?

It is almost impossible to completely eliminate internal parasites in sheep. Most sheep, when tested, will have at least a small fecal egg count of parasites. This is largely because sheep have tiny fecal pellets that disintegrate easily and therefore release worm larvae with ease.

Not only that, but sheep graze close to the soil surface – and consequently, to the feces. They acquire immunity to parasites slowly, with heavy stocking rates and poor pasture rest periods contributing to heavy parasite loads in the soil.

The symptoms of heavy parasite infestation vary in sheep depending on the types of intestinal parasites and how high the parasite loads are. However, you might notice symptoms such as these (ranked from the most common to the least):

  • Anemia (often accompanied by bottle jaw and pale mucous membranes)
  • Diarrhea
  • Fever
  • Coughing
  • Nasal discharge
  • Rapid breathing
  • Failure to thrive
  • Paralysis (rare)

What is the Best Dewormer for Sheep?

what is the best dewormer for sheep

There are several dewormers on the market that are approved for sheep.

It’s important that you rotate through these and not rely heavily on one product in isolation. That’s because overuse of a specific category of drug can lead to parasite resistance that will make the problem extremely difficult to treat.

  • For lambs, Ivomec (ivermectin) and Cydectin (moxidectin) are recommended treatments.
  • If you have lactating animals, only give Rumatel – this is the only one that is approved for lactating animals.
  • Valbazen (albendazole) should not be used during the first trimester of pregnancy for an ewe.
  • Other dewormer options include SafeGuard/Panacur (fenbendazole) and Prohibit (levamisole).

There is no single best dewormer for sheep. You’ll need to look at which types of parasites are causing problems for your sheep and decide on a dewormer product that will work accordingly.

Here’s more information that you can use to help break things down a bit further for you.

Deworming Sheep Naturally

While chemical dewormers tend to be the most effective (and reliable) at getting rid of heavy parasite loads in sheep, there are steps you can take in a parasite control program, too.

For instance, you can administer sheep garlic and garlic juice. Parasites tend to not be fond of the strong garlic smell and will generally steer clear.

Giving your sheep supplements such as apple cider vinegar, molasses, and B12 can help make the garlic more palatable while also reversing some of the effects of anemia caused by parasite infestations, too.

Diatomaceous earth and various herbal products have also been recommended to treat parasites in sheep, though the results have been mixed in most scientific studies.

How Do You Give Sheep Wormers?

Most people choose to administer dewormers with drench guns or syringes. This is cheaper than the alternative, which is using a disposable tube of paste. A drench gun is also more economical and faster if you’re administering medicine to a large flock of sheep.

Here is a quick video that shows you how to administer dewormer medication to sheep with an oral drench:

The dosage varies depending on the size of your animal and the kind of drug that is being used, so be sure to consult the label on the product you purchase for accurate information.

When Should You Worm Sheep?

Work out a deworming schedule that fits into your farm’s annual flock maintenance chores. Some people choose to worm their sheep on the same date they trim hooves or shear.

You can also separate ewes into breeding groups with different rams. This point of separation is another opportunity to administer a dewormer.

Lambs tend to be more susceptible to internal parasites so it’s a good idea to set up an aggressive deworming regimen to deal with them, too. Start deworming lambs when they are eight weeks old and do so monthly or bi-monthly until they are a year old.

It’s also a good idea to worm ewes about two to four weeks prior to lambing to prevent them from passing parasites on to the lambs. Adult lambs other than those that are lambing should be dewormed two to four times per year (or more frequently, if you suspect a heavy infestation).

If you are raising sheep for meat or milk, be sure to pay attention to the withdrawal periods as listed on the medications.


FAMACHA scoring is another system you can use to determine whether your sheep need to be dewormed. Although the recommendations above can be helpful when it comes to setting up your own timeline, treating your sheep for internal parasites when they don’t actually need it is a good way to create drug-resistant worms.

Therefore, it’s a good idea to treat only when absolutely necessary.

The FAMACHA system involves looking at the eyelid color of a sheep to determine its level of anemia. It includes corresponding shades that will help you evaluate whether treatment should take place immediately, within the near future, or not at all.

Other Tips for Deworming Sheep

deworming sheep naturally

Using a chemical dewormer isn’t your only option when it comes to managing the internal parasites of sheep.

The most important thing you can do, in fact, is to practice good pasture management. Don’t let your sheep feed directly from the ground. Use a feeder to administer a mineral supplement and grain. Keep the water clean and free of feces, too.

When you bring new sheep onto the farm, isolate them for at least 30 days and aggressively deworm them.

Use clean pastures when grazing sheep, ideally those that haven’t been grazed by sheep for at least the last six to twelve months. Allowing sheep to graze after cattle or other animals is generally okay, since most parasites are species-specific.

Remember that most worm larvae (up to 80%, in fact) reside in the first two inches of grass. Sheep that are allowed to graze taller forages will have fewer parasite problems.

Last but not least, consider the genetics of your sheep when you’re deciding on a breeding plan for the fall. Animals who exhibit good resistance to internal parasites are likely to pass this trait onto their offspring.

Be thoughtful about your plan to address internal parasites and deworming on your farm. With a bit of planning, you’ll be able to keep most problems at bay. For more deworming tips, check out this guide to deworming cattle.

Frequently Asked Questions

1. What does the term “anthelmintic” mean?

This is a formal term for “dewormer”. Anti-parasitic drugs are called anthelmintics, and they are available in a wide variety of forms, including pour-on, injectable, paste, drench and bolus. There are also anthelmintics that can be mixed into feed.

2. What is the best way to give an anthelmintic drug to a sheep or a lamb?

Oral products are always preferable for these animals. Look for boluses and drenches because oral formulations are most effective in sheep and lambs. Also, they have less of a tendency to promote drug resistance. This is why these methods of delivery are the only ones that are FDA approved for lambs and sheep in the United States.

3. What is targeted selective treatment (TST)?

TST is a practice of deworming that focuses on animals known to be parasitized rather than on doing blanket deworming of entire herds on a schedule. When using this method, the shepherd takes a very pro-active approach that integrates a holistic mix of parasite control methods, including genetic selection, controlled/zero grazing, mixed species grazing, pasture rotation and rest, as well as use of alternative forage.

4. Is it alright to mix one type of dewormer with another?

It is never advisable to mix drugs because they are unlikely to be chemically compatible. It is alright to do combination treatments of anthelmintics. To do this, you would give a full dose of one type of dewormer on one occasion and then give a full dose of a different type on a subsequent occasion. Doing this helps eradicate more types of parasites, and it helps avoid drug resistance.

5. What is copper oxide wire particle (COWP) deworming?

This type of deworming treatment alternative that can be used in place of synthetic anthelmintics. This product should not be confused with copper sulfate, which can cause sheep to suffer from copper toxicity. COWP can be purchased as a bovine copper supplement in large doses (12.5-25 grams). For use with sheep, the product must be repackaged into .5-1 gram boluses for lambs and 1-2 gram boluses for ewes. Consult your vet before using this type of dewormer.

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