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November 2014
The "silver bullet" of worm control in small ruminants



By Paul Casey
Heifer Project International
Perryville, Arkansas

. . . or at least what I think is the closest thing. It is not administered orally, intramuscularly or subcutaneously. It is not reconstituted or refrigerated. In fact, the sheep don’t even need to put in the corral. Interested? Then read on. But beware; it may be nothing more than the ramblings of a sheep grazier.

I manage a 60 ewe sheep flock at Heifer Project International’s Ranch in Perryville, Arkansas. About 10 years ago, we started looking at alternative methods of controlling gastrointestinal parasites in sheep. We tried garlic juice, papaya seeds, pumpkin seeds, an herbal dewormer, grazing chicory, grazing sunn hemp, and intensive rotational grazing. In the end, rotational grazing was the only practice we kept.

Using 120V and/or battery powered chargers, poly posts, poly wire, and temporary waterers, sheep were moved to fresh forage every 2-4 days, each April through November.

We implemented stringent culling and rotational grazing at the same time and within a few years parasite problems in the ewes were nearly non-existent. Some years, we did not have to deworm a single ewe. With the exception of the chicory and sun hemp trials, nearly all grazing was on permanent pasture. Cool season forages were predominantly fescue, ryegrass, clover, and vetch. Summer forages were dallisgrass, bahiagrass, foxtail millet and crabgrass.


While we had minimal problems with the ewes, obtaining consistently good lamb weight gains, especially after weaning (at 4-6 months old) was very difficult. Had we not pushed the lambs so hard by only deworming at FAMACHA© 4 and 5, they may have performed better. We had only one effective

dewormer left, and my goal was to use it as little as possible. Grazing more summer annuals and speeding up the rotation may have helped improve the weight gains.

While I know that our strict ewe culling and ewe lamb selection helped reduce our worm problems, I believe the grazing is what made it successful. By controlling what the sheep eat, when they eat it, and how long they are on a given section of pasture, the manager controls forage intake, forage quality, plant regrowth, and relative ingestion of parasite larvae. Grazing management is the most powerful tool we have for maintaining animal health and performance. While many people use FAMACHA© scores as an indicator of parasite load, I use it as an indicator of my management (pasture and breeding).

Keeping sheep behind an electric fence is not likely as hard as you have heard it is. A good strong charger, poly posts, poly wire and persistence, on your part, is all that is needed. I have rarely used more than 3 strands of poly wire and frequently used 2 strands. If sheep have enough quality forage to eat and the fence is kept consistently hot, rotationally grazing sheep is easy.

Was this what you expected for a silver bullet? I hope so. We need to look at anthelmintics, not as a tool in our tool box, but as a band aid to fix a management problem.

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