Are parasites a limiting factor in your flock/herd?

The parasites that infest sheep can be an enormous drag on sheep production. Year in and year out, they probably cause more death and disease in some producers’ lamb crops than any other single factor, including predators. The days when the answer to parasite management was to drench all the sheep every month are behind us. Parasites have started to evolve resistance to various classes of dewormers. The problem with chemical resistance is so pronounced in some parts of the Southeast US that there are farms where no wormer works anymore, and there’s at least some degree of chemical resistance nearly every place where worms are a problem. The first step in knowing how to manage parasites in your own farm is to know what’s going on in your flock’s guts and in the environment they inhabit. The second step is to know what environmental factors play into parasite reproduction and infectivity. In the final analysis, the answer for how to manage parasites is probably going to be a little bit different in every flock. The standard life cycle of parasites Most internal parasites of sheep follow the same basic life cycle.

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2 thoughts on “Are parasites a limiting factor in your flock/herd?

  1. Thank you for this concise explanation of the worm life cycle. Looking forward to the next segment.

  2. Great article. A few resources available to help sheep and goat farmers with parasite management include: “Sorting Through the Information on Sheep and Goat Parasite Control: A Decision Making Support Tool” located at, recordings of parasite management presentations available under Parasites at and various articles under the Parasite tag at .

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