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December 2012
The periparturient egg rise


Susan Schoenian
University of Maryland Extension

The periparturient egg rise is a well-documented phenomenon in small ruminants: a temporary loss of naturally-acquired immunity to gastro-internal parasites that begins approximately two weeks before parturition and continues for up to eight weeks after. During this period, the ewe or doe has a reduced ability to deal with worms.


The intensity and distribution of the periparturient egg rise varies by breed, individual, and season. While the exact mechanism is not fully understood, the periparturient egg rise is believed to be the result of various nutritional and hormonal factors.


When lambing and kidding occur in the spring, the eggs deposited during the periparturient egg rise are largely responsible for the infections that lambs and kids acquire during summer grazing. For this reason, the periparturient egg rise is also called the “spring rise.”

In an indoor lambing and kidding environment, the effect of the periparturient egg rise is minimal because the eggs are not being deposited onto pasture and females are not continuously ingesting new larvae.

Several strategies can be implemented to minimize the effects of the periparturient egg rise. The traditional approachhas been to deworm ewes and does prior to lambing/kidding (within 1 month) or shortly thereafter (within two weeks). A pre-breeding treatment to eliminate hypobiotic (arrested) larvae is another commonly used strategy.

When implementing these strategies, it is important to use an anthelmintic that is effective against hypobiotic larvae. While most of the commonly-used anthelmintics are considered to be effective against hypobiotic larvae [1], the macrocylic lactones (Ivomec® and Cydectin®) are considered to be the most effective. Morantel (Rumatel®) is not effective against hypobiotic larvae.

Strategic nutritional supplementation, especially protein, is another way to counteract the effect of the periparturient egg rise. Feeds rich in by-pass protein are especially advantageous. Nutritional supplementation makes sense, since the loss of resistance is occurring at the same time the female’s nutrient requirements are increasing.

Current NRC requirements may encompass an influence of low levels of parasitism (all recommendations are for confined animals), but there are no clear recommendations available for the effects of subclinical levels of parasitism on metabolizable protein requirements of sheep and goats [2].

2009. Sustainable worm control strategies for sheep. 3rd edition. SCOPS.
2007. Nutrient Requirements of Small Ruminants. National Academies Press.

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