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January 2015
Silver bullet seconded:
can the right grazing strategy control parasites



By Dave Scott
Livestock Specialist
Butte, Montana

Can the right grazing strategy control parasites? I must add an enthusiastic “second” to Paul Casey’s November 2014 Timely Topics. We have a 200-ewe operation in southwest Montana that is pasture-based. Now, you may be thinking that Montana and the dry ol’ West can never have as many parasite problems as the Southeast and Northeast. However, under the right conditions, we certainly can -- and do.

The conditions are: irrigated pasture and lots of sheep. If you think about it, when your pastures are sprinkle-irrigated with 0.70” of moisture twice a week, the micro-environment way down there in that jungle of stems and leaves, manure, and soil is quite similar to a Louisiana paddock in June. Just add the sheep and goats, and presto, you have Haemonchus!

Within five years of that startup, we were deworming our ewes and lambs three to four times a summer and once in the fall. We did not know anything about FAMACHA© back then, so the shotgun blast was the order of the day. When the white wormers lost their effectiveness, Ivomec® was the only dewormer that we had left. Uh oh!

Here’s what we did. We divided up our 30 acres of pasture into 36 paddocks with temporary fencing (electric nets), increasing our pasture rest from 22 days to 35 days. Next, we moved the sheep to a new paddock every day. Lastly, we made every effort to exit a paddock leaving six to eight inches of grass behind. Then we ratcheted our deworming down, down, until, after three years, we were not deworming any lambs or ewes at all.


It worked. In 2013, we ran 180 ewes and 280 lambs on the 30 acres from May 1 until August 31. We dewormed no lambs and no ewes. We did not FAMACHA® that year, but the lambs looked good and 74 out of 82 ewe lambs conceived that fall. Not too bad. By 2014, we had learned  how to FAMACHA®

and we found 16 out of 330 lambs with a score of 4 or 5. The rest were scored 1, 2, or 3 and were not dewormed. 


For a more complete description of our grazing strategy and how it has helped us, check out the ATTRA video, Intensive Grazing: One Farm’s Setup, available at:

I must agree with Paul. There also may be a “stocking density tipping point” where the parasites overwhelm even the best strategy.  Just the same, while “silver bullets” are not often found on street corners, or in this case, farm pastures, smart grazing has the hue. Try it!

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