Grazing the Parasites Away: Management Tools to Lessen Pasture Parasite Loads

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If your animals are on a quarterly deworming schedule, as many are, the end of March means it’s almost time to run those animals back through the chute for round two for the year. Lately, producers are finding that sticking to the “same ol’ same ol’” when it comes to dewormers just isn’t cutting it. Parasites are becoming more and more resistant, and farmers are having to become more and more creative and strategic with their deworming methods to keep the parasite loads in their herd or flock at a manageable level. We tend to scratch our heads about what new combo of dewormer to use, when the best time to deworm is, how to make our dewormers more effective, but maybe our thinking should focus more on “how can I adjust my management practices to decrease the parasite load on the farm in addition to dewormer?”  Keeping parasite loads at bay is not just a matter of deworming, but how you manage your farm, especially in the coming months when the weather is warming and the grass really starts to grow.

So what kind of small adjustments can be made?

Multi-species Grazing

While this method is not as practical for those that have only one species on the farm, or have no desire to add another species on the pasture, multi-species grazing can lessen the parasite load on pastures. Many of the effects that parasites have on our grazing animals are species specific. Cattle parasites cannot survive in sheep and goats, and small ruminant parasites cannot survive in cattle. Horses can also be thrown into the mix, as they do not have the same parasites as the others.

Multi-species grazing can be done in two ways. All animals can all graze in the same area at the same time, and be taken off at the same time to let the pasture rest. In this system, the parasite loads in the animals decrease because there are less larvae consumed by the one species. The parasite load on the pasture is spread out over multiple animals of multiple species. The animals can also graze in a leader-follower system. In this system, one species graze on the pasture first and then they are taken off of the area. After an adequate rest period (depending on factors such as forage type, grazing height, weather conditions, etc.) the next species is put on that same pasture.

Grazing Height

This factor is relatively simple. Most parasites are found on the first 2-4 inches of forage growth. By not allowing your animals to graze below this 2-4-inch mark, it is likely that they will not eat low enough on the plant to ingest the parasite larvae. This results in a lessened parasite load in the animal, and less eggs put back into the pasture from the animal.

Stocking Density

Do not overstock your pastures! When pastures are overstocked, two things can happen. The most obvious issue with overstocking is that there will be less forage available for each animal, which will result in forages being grazed lower. As stated earlier, shorter grazing heights will lead to a heavier parasite load, as parasites are found on the lowest portion of growth. The second issue is a little less obvious. When animals have a heavy parasite load, they shed eggs through their feces. With too many animals defecating in one area, the amount of eggs on the pasture has the potential to skyrocket, and if animals are grazed on this pasture when these eggs hatch, so will the parasite load in these animals.

Pasture Rotation

Rotational grazing has been a hot topic in the forage world lately. Not only does it benefit soil and forage quality, it can also reduce the parasite load in your animals. Allowing pastures to rest gives the parasites time to hatch, complete as much of their life cycle as they can without a host, and then die off. Best practice is keeping livestock off of a pasture for 4-6 weeks before grazing, as the life span of parasites vary between species, and with temperature and conditions. If you want a pasture that it totally ‘clean’ to graze your animals, the pasture needs to rest for roughly 12 months to allow all of the parasite eggs and larvae to die off.

These management tools are a great way to lessen the parasite load on your animals, and to increase the efficacy of your deworming program. Less parasites mean less resistance to dewormers, and a more efficient and effective deworming system.