Feature Manage Parasites Strategically in Saskatchewan Herds Parasites don’t rank very high on the decision-making list in livestock management, but they can still lower production and decrease return by their insidious impact on herd health. Beef Business spoke to Dr. Doug Colwell, principle research scientist at Agriculture and Agri-Food Canada based out of Lethbridge, Alberta, to identify the types of parasites common to Saskatchewan cattle, options for treatment and how to manage parasites in a herd. Parasite Types The main parasites found internally and externally in cattle in Saskatchewan include the nematode parasites, the most common internal parasite. Also known as roundworms, they can be found in various parts of cattle intestines. They are quite prevalent in Saskatchewan and research by Dr. Fabienne Uehlinger found at least six species of roundworms in beef cattle in the province. For example, one very pathogenic species of roundworm, Ostertagia ostertagi, is known as the brown stomach worm or medium stomach worm. It can be found in the large intestine in cattle and can cause serious health effects. Roundworms can lead to production inefficiencies such as weight loss, poor feeding, diarrhea in calves and reduced milk output and reproductive problems in cows. While many cattle in Saskatchewan are exposed to the roundworm parasite, few become infected because there are insufficient worm eggs or third stage larvae on pastures to overcome a healthy cow’s natural immune response. The coccidia is a single cell parasite common in cattle. Some species are more common in early spring and later in the summer. The Eimeria zuernia species has caused considerable problems in Alberta. It tends to be brought on mostly by stress, such as during branding of calves. Calves are better able to fend off the parasite in a low stress situation. Most of the coccidia are not pathogenic and cattle seem to be able to control the parasite infection through their own immune response.
NOVEMBER 2019
Lice is an external parasite found in Saskatchewan cattle that is found in two types – chewing lice and sucking lice. There is only one species of chewing louse and there is generally one species of sucking louse. “We tend not to have all the species on any one group of cattle,” Colwell stated. The next most prominent parasite is the horn fly. It is found externally on cattle and is visible to producers. The tapeworm is an internal parasite which does not cause too much damage. “In half of the cattle we see, we will find eggs of the tapeworm,” Colwell said. The liver fluke parasite is occasionally found in cattle in Saskatchewan. “For the most part, we’ve been able to find it in the Cypress Hills area, but it is not common in the plains area because it is just too dry there to develop very well,” Colwell explained. There are two species, and one causes a significant amount of damage. The liver
fluke has three different hosts: the snail, the ant and the grazing animals. Seasonality Parasites are impacted by seasonal differences. The prevalence of parasites is determined largely by temperature and humidity. For example, brown worms are primarily found inside the cattle in the summer. There are also free-living stages of this worm that can overwinter on pasture. It is estimated that about 5% of them survive the freezing and warming that occurs in the winter. In the past, it was assumed that brown worms did not survive the winter and cattle would pick up the parasite in the pasture in the summer from an intestinal infection. However, now it is known that brown worms overwinter on the pasture, meaning that cattle can acquire the parasite as soon as they are on grass in spring. continued on page 16
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