As spring ramps up, so do parasites in livestock. Parasites, however, don’t have to have to take over your operation.
“Spring is typically the most active time of year for internal parasites,” Andy McCorkill, a University of Missouri livestock specialist said. “They often use the animal’s intestinal tract as a host through the winter months and then start shedding eggs through feces in the spring as the temperatures start to rise. In the heat of the summer, they really slow down as they can’t take the excessive heat very well.”
According to McCorkill, taking a few steps to prevent an infestation will save time, labor and money down the road.
“Like with many ailments in life, an ounce of prevention is worth a pound of cure,” he said. “Taking efforts to reduce contact with internal parasites will help reduce the likelihood of having parasite problems in the first place.”
McCorkill said one best preventative measures is improved management, specifically grazing management. Because most internal parasites tend to be more concentrated on the bottom 3 to 4 inches of the plant, close to the ground; keeping animals from grazing tight will decrease the number of parasite larvae ingested by the herd.
“Additionally, the lifecycle of most economically devastating internal parasites is relatively short, generally less than 30 days,” McCorkill said. “Setting up a rotational grazing system that allows for extended rest periods for pastures can potentially reduce the incidence of larvae consumption and help break the parasite cycle.”
To treat external parasites, McCorkill said there is not a “one-size fits all” answer, but he did offer three common methods of treatment:
1) Feed through additives such as Altosid: “Altosid works well if started early because they break the life cycle of horn flies in particular,” he explained. “Unfortunately, it doesn’t work with all types of flies and other external parasites so it is limited in its usefulness. Furthermore, flies don’t respect boundary fences; if you have cattle against a neighbor who doesn’t feed Altosid, his flies could find their way to your cattle.
2) Fly tags. McCorkill said fly tags are a good choice to control flies and other external parasites that congregate around the head of the animal, but their range of effectiveness doesn’t generally provide control for the whole body, leaving room for udder or underline infestation. “Flies have the ability to adapt resistance to chemical treatments relatively quickly so steps must be taken to reduce the likelihood of developing resistance to a particular chemical compound,” he said.
3) Pour-on, spray, back rubber and dust bags. “They share many of the same active ingredients as the fly tags so they carry the same caution about resistance issues,” McCorkill said. “With adequate coverage, they do provide fly control for the entire body, which is a nice feature. Perhaps the biggest drawback is the duration of efficacy; it is quite variable based on precipitation, but in general is much shorter lived than the fly tags and diligent use of feed through methods.”
McCorkill recommended least two of the methods outlined, but there are times when all three are needed.
“Just remember to rotate active ingreagainst internal parasites, if labeled for such use and if used correctly. The problem we often run into with pour-ons for internal use is getting it applied in a manner that allows the product to soak into the skin,” McCorkill explained. “In order to get it to work, the use of an applicator placed as close to the animal’s skin as possible is imperative. The hair coat sometimes gets in the way. Pour-on products also require some ‘dry’ time to soak in. It isn’t advisable to treat livestock when weather is in the forecast. Products labeled for both internal and external parasites available in a pour-on formula include doramectin, eprinomectin, ivermectin and moxidectin, to name a few.”
He added that he generally advises livestock producers to use the method that is closest to the major parasite threat. If external parasites such as lice, ticks, flies and the like are the major problem, a pour-on application is probably going to work better, whereas if internal parasites are more serious, an injectable product will be more advisable. “Sometimes, it makes sense to use an injectable dewormer and still utilize some sort of more targeted pour-on product to control external parasites. It really depends on the situation,” McCorkill said.

OFN Site ManagerFarm HelpMissouriAs spring ramps up, so do parasites in livestock. Parasites, however, don’t have to have to take over your operation. “Spring is typically the most active time of year for internal parasites,” Andy McCorkill, a University of Missouri livestock specialist said. “They often use the animal’s intestinal tract as...The Ozarks' most read farm newspaper, reaching more than 58,000 readers in Missouri, Arkansas and Oklahoma