How do I manage internal parasites in multispecies grazing?

Answer: Perhaps one of the most notable benefits of multispecies grazing is its effect on parasite management. Cattle will consume parasite larvae such as the Barber Pole Worm, which only infects sheep and goats, and because this worm is incompatible with cattle, the worms will die. The same thing happens when small ruminants consume parasites that are indigenous to cattle. Because of parasite larval incompatibility between species, cattle can be grazed after or with small ruminants to reduce the incidence of larval infection.
Managing sward height is key in controlling internal parasites. As worm larvae emerge, they travel up the leaf blades of grasses to position themselves right in the way of a grazing animal as it eats, but they usually don’t climb higher than four inches. As long as you keep grazing to the top leaves of the sward, and move the animals before they graze too low, you can significantly reduce infection. Try to maintain at least a 6-inch residual after grazing. Also, give the paddocks a nice long recovery period. This is not only good for pasture health and resiliency; it also allows parasites to die off in the pasture before they can be consumed by a grazing animal. Use a 40-day recovery period at the very least in pastures you know to be infected by parasite larvae.
In addition, you can also use a shorter grazing period. Again, this benefits pasture health because plants begin to regrow around three or four days after they have been grazed, and getting the animals off to allow for regrowth is a key management consideration in multi-paddock rotational grazing. But it also works to break the parasite’s life cycle. By moving the animals off a pasture before day four, you’ve effectively moved them before the larvae are able to move up into the sward to be consumed by animals.
If you have a pasture that is infected with larvae and are having a hard time ridding the herd or flock of parasitism, you can take the pasture out of the grazing cycle for a few rotations. Steve Hart of Langston University recommends resting an infected pasture for six weeks in the hot summer, taking the forage off as hay at four weeks, then resting it another two weeks. After this, the parasite’s life cycle should be broken and you should be able to continue grazing as usual (Hart, 2014).
Think about your common areas too, such as a barn lot or shady areas where animals congregate. It is probably best to provide water in the pasture, and not in a central location where animals will be continuously grazing and re-infecting themselves.
Some plants are known to reduce parasitism in livestock. Consider adding some tannin-producing plants such as Sericea lespedeza, sainfoin, or chicory to your pastures. These plants have been known to cause as much as a 50% reduction in fecal parasite egg counts (Hart, 2014). See the ATTRA publications Tools for Managing Internal Parasites in Sheep and Goats: Sericea Lespedeza and Tools for Managing Internal Parasites in Sheep and Goats: Pasture Management for more information.
Animals can deal with a certain amount of parasitism. The key here is maintaining a healthy herd or flock and fostering natural immunity through good nutrition, clean fresh water, and pasture access. However, one of the best methods for controlling parasitism, in addition to observation and targeted treatment, is culling repeat offenders and selecting for resistance when breeding and acquiring new animals.
You’ll never be able to completely eradicate internal parasites in livestock. However, an integrated management system with combined livestock species can certainly make a dent in their populations. There will always be some parasites in a herd or flock, and otherwise-healthy animals can deal with a slight parasite load. Additionally, cattle can usually handle parasites much better than small ruminants. The goal is to manage the parasites that remain in a herd such that treatments can be effective against them. This population of parasites in the herd or flock is called refugia. Essentially, this population remains relatively unexposed to dewormers and reduces the incidence of dewormer resistance.
For more on dealing with small ruminant parasites, including refugia and dewormer resistance, see the ATTRA publications Managing Internal Parasites in Sheep and Goats and Managing Internal Parasites in Sheep and Goats: Success Stories, which includes Paul Casey’s description of how they use multispecies grazing at Heifer Ranch.
Ready for more information on the principles and practices of multispecies grazing? Check out the ATTRA publication Multispecies Grazing: A Primer on Diversity.
Reference: Hart, Steve. 2014. Parasite Control with Multispecies and Rotational Grazing. Langston University.