Managed Grazing to Reduce Parasites in Lambs on Pasture

My name is Melanie Barkley, and I'm a livestock educator with Penn State Extension.

The sheep industry in Pennsylvania currently ranks 6th in the country for the total number of sheep operations in a state, and 15th for the total number of sheep and lambs in a state.

One of the major challenges to sheep producers in Pennsylvania, and across the United States, is internal parasites. These parasites have a negative impact on lamb growth and ewe milk production, and can lead to death of the animals if not controlled or treated.

In addition to these challenges, internal parasites have developed a resistance to the anthelmintics, or deworming products, used to treat sheep and goats. Therefore, sheep producers must find alternative methods to prevent internal parasites in their animals. These methods include rotational grazing practices and genetic selection for individuals with parasite resistance.

My name is Dr. Tara Felix, and I'm an extension specialist here at Penn State University. We're here at one of our sheep farms on campus, and we're doing a trial on managed grazing practices with growing lambs.

The largest challenge that we deal with, with pasture-reared lambs, is parasite infestation.

And in a survey of Pennsylvania producers, approximately 2 lambs are lost per year for Pennsylvania producers to parasite infestation. In addition, those producers stated that 12 lambs per year show reduced growth on their operations because of parasite infestation.

My name is Jasmine Harris, I'm a master's student for Dr. Felix at Penn State University, and I am the lead graduate student on this project. The parasite we're looking at is Haemonchus contortus, also known as the barber pole worm. It's very detrimental to goats and sheep, and with the growing resistance to the treatments called anthelmintics, it becomes important to find some type of way to reduce the parasitism in these lambs without having to use those anthelmintics that they're already immune to.

My name is Dave Hartman, and I'm a member of the Penn State Extension livestock team. One of the things from an agronomic standpoint, and even from an animal nutrition standpoint, most of us would agree that some sort, or some phase, of a rotational grazing system is a good practice to employ when grazing livestock. So in a good rotational system, we should be able to keep livestock on a fairly even plane of nutrition. Farmers are innovative, so there's lots of different ways pastures can get dragged in. I've seen pictures in magazines of, you know, things that people have rigged up.

It doesn't have to cost much money.

In addition, by moving those lambs throughout the pasture, and applying other agronomic practices like mowing the pasture and dragging the pasture, we provide opportunity to break up those fecal pats where the concentration of parasite eggs might be greatest, and spread those out and desiccate those eggs, such that by the time the lambs come back to that next grazing rotation, they won't have as high incidence, or as high a prevalence, of those fecal eggs on the pasture, thereby, again, reducing the incidence of those lambs to consume those fecal eggs and become infected with the parasite. By far and away, the easiest test that we have on farm is the FAMACHA Score. So, the FAMACHA Score is where we look at the eye, and determine the anemia status of that animal based on the coloring around the eyelid.

If a farmer or producer decides that after the FAMACHA check, if they have poor scores and they decide to take a blood sample, send it off to the lab, and the lab is where it goes into a tiny, skinny tube, which will go into the centrifuge to separate the actual layers of the blood. From that, you take the comparison of the red cell to the whole column, and that'll give you about a percentage of what their packed cell volume would be. So based on that percentage, if they only have 20% of their whole column of blood as red blood cells, at this point in the project, we would deworm. If a producer has a number that's less than 15%, it would definitely be vital to deworm, because that's a heavy sign of anemia.

So, one of the ways to determine the parasitism in the lambs is to do a fecal egg count. After collecting a sample of the feces directly from the animal. The McMaster technique uses a McMaster slide, which has a chamber, and using that chamber, you give a rough calculation as to how many eggs per gram there are in the animal, which can give you a rough estimate of the actual adult population that could be infecting the animal.

One of the things we know is that raindrops can actually splat those larvae farther up the blade of grass, and cause them to move farther away from that 3 inches, where we think they typically reside, to as much as 8 inches. In addition, an incredibly dry summer can essentially put those eggs into a stagnant state, and then when rain comes back and there's enough moisture, it comes back, it'll pull those parasites, have an influx of those parasites coming out again, and causing more issues.

As always, Penn State Extension recommends you consult with your veterinarian for best management practices on your farm.

We are on about day 60 of the current trial. We treated animals on day 1, and have not had to provide anthelmintics to animals since. Now we're operating on a 1-to-3 day rotation, which is pretty intense. Most operations won't rotate every 1-to-3 days, but that rotation is just helping us be able to avoid the use of those anthelmintics.