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Photo of proper drenching technique

Proper drenching procedure is essential for dewormer efficiency. Make sure the animal’s chin is level and that the nozzle dispenses behind the tongue. Alternatively, use an injectable for internal parasites.

Worms, worms and more worms…
Controlling parasites in sheep and goats
By G.F. Kennedy, DVM, Pipestone Veterinary Services
Should you run lambs on pasture?
I have received a number of inquires regarding parasite (worm) control. I recently posted a series of short articles on Facebook to address this topic. These posts have been popular, so we've combined them below to send to a wider sheep audience.
The short answer to the question is: No, I do not recommend running lambs on pasture.
Let’s review the situation: We have a ewe and a lamb; the ewe has some resistance to parasitism depending on the individual animal and the breed. The lamb has virtually none. The ewe in the beginning supplied an adequate amount of milk to sustain life and growth. It’s later now and the milk flow is diminished and the lamb needs extra nutrients lush wet grass doesn’t provide. Now add the fact that lambs have virtually no parasite resistance and we have the perfect opportunity for severe parasitism to develop.
Ewes and lambs which have been closely monitored through lambing have had a successful life until turned on pasture. Now the lamb is on its own to fend with worms and coccidiosis while it attempts to survive on inadequate nutrition.
By the time you factor in the dead, lambs weaned in the fall weigh no more than they did as a group when initially turned out. When placed on feed, lambs will have a 7:1 conversion verses a 3:1 conversion if they never saw grass. And they generally are marketed at a time when prices are seasonally lower.
What’s the solution? If you have extra grass, run more ewes.
Dewormers explained—
When it comes to wormers there are a lot of choices. Ivermectin drench and injectable, Cydectin drench, Valbazen, Safe-guard, Dectomax, levamisole and a feed product, Goat Dewormer Concentrate containing Morantel Tartrate. They are all effective in the right situation. Basically, it boils down to:
  1. White wormers such as Valbazen and Safe-guard.
  2. Ivermectins such as Cydectin, Ivomec, Dectomax and levamisole, which is marketed as Prohibit or LevaMed.
  3. The outlier is the goat dewormer.
So which should you choose?
I see no reason to use a white dewormer unless you are in a fluke area and then I would choose Valbazen. When using white wormers the dosage can be increased without a problem.
As for the ivermectins, I prefer Dectomax. An added benefit is that it’s effective against heel mites. Dosage is 1cc per 110#. Overdosing ivermectin products isn’t necessary, but even so it’s not usually a problem. I once had a brittany spaniel named Tramp who had demodectic mange and immunodeficiency. He received ivermectin every day of his life for the last five years and died when he was 13 years old of other causes.
Additional Resources:
I ignore tape worms—the only worms seen without the aid of a microscope. Tapeworms are nonpathogenic. You can get rid of them, but they will return until the animal develops an immunity. There is no economic significance to treating for them.
Goat Dewormer Concentrate is an interesting alternative to drenching or injection and is very effective. My concern is how do you feed it accurately to each animal?
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Combination dewormers—Should they be used?
In the most recent Wool & Wattles Newsletter (published by the American Association of Small Ruminant Practitioners), there is an editorial on the use of combination wormers by Ray Kaplan, parasitology professor University of Georgia.
I haven’t been supportive of combination worming in the past, but after reading the article I may be wrong. It is common practice in other countries. In control of internal parasites, management should always come first. I will try to summarize the high points from the article.
  1. In other countries wormers are marketed in combination. Not in this country.
  2. You can’t just mix two wormers together because they may not be compatible.
  3. Withdrawal time is based on longest of the wormers used.
  4. You can give them simultaneously; you could drench with two or you can drench with one and inject the second one.
  5. You wouldn’t use two white wormers simultaneously, but two different types such as Dectomax and levamisole.
  6. Theory is that if one wormer kills 90% and the second wormer kills 90% of the 10%, then you have 99% efficiency.
  7. If you have wormers with 50% efficiency even combination of three won’t get it done.
  8. If the efficacy of your dewormer is greater than 80% you may not notice a difference when applied singly vs. combination. However, the impact on the further development of resistance could be quite large.
  9. Combination wormers are less likely to cause resistance than by rotating wormers.
I have never supported the use of combination worming but I suspect this article has changed my thinking.
G.F. Kennedy, DVM
G.F. Kennedy, DVM started at Pipestone Veterinary Services in 1960 after graduating from Iowa State University’s College of Veterinary Medicine. He is a nationally recognized sheep health and production expert. Dr. Kennedy’s personal interests have always included raising purebred sheep, from Suffolks and Rambouillets to his current flock of Dorpers and Katadins.
* The views and opinions of the authors who have submitted articles to belong to them alone and do not necessarily reflect the views or opinions of, its staff or owners.
A note from Stan Potratz (Premier’s founder)
For decades I tried to raise lambs on grass here in southeast Iowa. Which meant we fought both worms and coyotes…with all the tools at our disposal at the time. Sometimes we won and sometimes we lost. That our grass quality declined rapidly in the summer heat was a factor.
Now we do as Dr. Kennedy suggests. We don’t have a grass-fed lamb market, so this works well for us.
  • Lambs don’t go on pasture unless it’s not “seen” a sheep for a year.
  • Most are fed inside on cheap Midwest grain/soy hulls, etc.
  • No worm issues.
  • No coyote issues.
  • Lambs do well.
That said, many producers have the opposite situation.
  • High priced grain.
  • Low cost grass.
  • Less summer heat so higher quality grass.
  • Premium market for grass-fed lamb.
And therefore the dewormer advice above to keep worm challenges low is critical. It also helps if you graze cattle (dilutes worm challenge).
Management tools to fight parasites
Phillips Auto Drench Gun
Phillips Auto Drench Gun — $141
Most reliable unit from Australia. Cylinder is more durable and ergonomic than others. 0–20 ml.
Auto Syringe & Drencher
Auto Syringe & Drencher — $32
Easy way to vaccinate or drench many animals without having to refill after each animal. 5 ml.
Dectomax® Injectable
Dectomax® Injectable —from $59
An injectable solution that will treat or control 7 types of parasites.
Cydectin® Sheep Drench — from $77
For use in healthy sheep to control 13 types of adult and larval stages of internal parasites.
Ivomec® Drench for Sheep — from $91
For treatment and control of adult and fourth-stage larvae for sheep only.
Prohibit® — $23.50
Broad-spectrum anthelmintic. Effective against the following nematode infections in cattle and sheep: Stomach worms, intestinal worms and lungworms.
Veterinary services, procedures, biologicals and drugs mentioned represent the personal opinions and clinical observations of the author. The author is not intending the response to be interpreted as recommendations without the consent of the producer’s own participating veterinarian. Premier 1 Supplies, LLC and Pipestone Veterinary Services, PLLC strongly urge that producers establish a patient-client-veterinarian relationship.
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