The Periparturient Egg Rise
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16The Periparturient Egg Rise: A phenomenon in small ruminants whereby the ewe/doe experiences a temporary reduction in immunity to gastro-intestinal parasites and it is associated with a rise in fecal egg counts. The periparturient egg rise occurs approximately two weeks before lambing/kidding, and can persist until up to eight weeks after parturition. During the end of gestation, and shortly after parturition, ewes and does have decreased resistance to parasites due to decreased immunity. The exact causes of the phenomenon are not fully understood; however, there is evidence to support the decreased immunity is due to the results of hormonal, nutritional, and photoperiod effects. Additionally, the increased stress on the dam from lambing/kidding and lactation further decreases her immunity. Because of the timing, the periparturient egg rise coincides with an increase in the number of susceptible animals. Furthermore, the animal age and stage of development, breed type, and season have a significant impact on the susceptibility to parasites. Young, growing animals that continuously graze permanent pastures are the most susceptible to parasite infections. Spring born animals are largely impacted by the eggs deposited on pastures when they graze summer pastures. Mature, dry animals are the least susceptible to parasite infections.
There are several strategies that can be implemented on farm to minimize the effects of the periparturient egg rise.
- Deworm only the animals that require treatment or would benefit the most for anthelmintic treatment. Incorporating the Five Point Check© for targeted selected treatment of animals is highly recommended. The Five Pont Check© incorporates utilizing FAMACHA© scoring to identify ewe/does that need deworming. Typically, ewes/does with FAMACHA© scores of 4 or 5 are dewormed.
- Increased protein in late gestation has been advantageous in minimizing the effects of the parasite burden. Feeds high in by-pass protein are especially helpful.
- Indoor lambing/kidding operations typically experience minimal effects because the eggs are deposited into bedding instead of on the pasture. This way, the animals are not continuously ingesting new larvae.
- With chemical dewormers, utilize a dewormer that is effective against hypobiotic (arrested) larvae. Research supports the macrocylic lactones (Ivomec® and Cydectin®) are the most effective against hypobiotic larvae. Again, use only targeted selected treatment of animals – deworming all animals is discouraged to prevent parasites becoming resistant.
- Select animals for breeding with increased resistance to parasite. Certain breeds have increased resistance to parasite infections. Parasite resistance is only a moderately heritable trait.
- Avoid overgrazing pastures. When overgrazed, sheep graze closely to the ground; therefore increasing the likelihood they will ingest larvae. Maintain pasture heights of at least 5 inches.
- Implement leader follower grazing. Susceptible animals graze before less susceptible animals (lambs before dry ewes)
- If possible, practice rotational grazing to improve pasture forage health and reduce parasite load.
The above strategies are not a comprehensive parasite control plan; however, the strategies can be easily incorporated into your operation to help reduce the impact experienced during the periparturient egg rise.