Changing Pastures? Beware of Last Season’s Parasite Infestation

It’s a common misconception among producers that a rotational grazing strategy helps provide protection from parasite infections. But nothing could be further from the truth according to Joe Dedrickson, DVM, Ph.D, large animal veterinary services, Merial. In fact, the use of pasture rotation as a means of parasite control may actually increase the risk.1
“Using pasture rotation as a sole means of parasite control is not effective,” Dr. Dedrickson says. “Many producers believe that if they vacate pastures for several weeks, they are providing enough time for the deposited eggs to become dormant. In reality, a three- to four-week rotation schedule allows time for the previously deposited eggs to become infective larvae – usually about the same time cattle are allowed back into the pasture.”
According to research conducted by the University of Minnesota, infective larvae can maintain viability even during the cold winter months.2 In the study, the larvae were found on pastures in the spring, even though they had not been grazed on since the prior summer.2
The fact that infective larvae remain in pastures long after they have been deposited should help producers understand the risks of using rotation as a parasite-control strategy.
“In addition to the data that shows the long viability of larvae, there is evidence to suggest rotation of pastures may even contribute to an increase in contamination,” Dedrickson says.
With the ineffectiveness of pasture rotation as a parasite-control strategy and the potential losses associated with parasite infestations, it is important for producers to adopt programs that work.
“An effective parasite-control program should include a protocol that breaks the actual life cycle of parasites and incorporates the use of a product that is long-lasting,” Dedrickson says.
“Conventional dewormers on the market today aren’t able to effectively interrupt the parasite life cycle. They only last between a day and up to 42 days with limited spectrum of control,” he says. “LONGRANGE® (eprinomectin), on the other hand, was specifically developed to be long-lasting, providing up to 100 to 150 days of parasite control.”
Dedrickson says the longevity of the product is what helps reduce the burden on the pasture. “Because it takes about 100 days of continuous parasite control to break the parasite life cycle, the use of LONGRANGE can help reduce parasite burdens on the pasture,”3,4 he says. “Ultimately, the use of a strategic deworming program that breaks the parasite life cycle can lead to beef cattle that have improved feed efficiency, have improved reproductive efficiency, produce higher carcass quality and have a stronger immune system to fight off disease.”
For more information and to find out how LONGRANGE can fit into your deworming program, visit
IMPORTANT SAFETY INFORMATION:  Do not treat within 48 days of slaughter. Not for use in female dairy cattle 20 months of age or older, including dry dairy cows, or in veal calves. Post-injection site damage (e.g., granulomas, necrosis) can occur. These reactions have disappeared without treatment.
About Merial
Merial is a world-leading, innovation-driven animal health company, providing a comprehensive range of products to enhance the health, well-being and performance of a wide range of animals. Merial employs approximately 6,000 people and operates in more than 150 countries worldwide. Its 2012 sales were $2.8 billion.
®LONGRANGE is a registered trademark of Merial. ©2014 Merial Limited, Duluth, GA. All rights reserved. RUMIELR1413 (01/14)
1Williams JC, Loyacano AF. Internal Parasites of Cattle in Louisiana and Other Southern States. Louisiana State University Agriculture Center Research & Extension. August 2001.
2Stromberg BE, Schlotthauer JC, Haggard DL, Vatthauer RJ, Hanke H,
and G.H. Myers. 1993. Epizootiology of helminth parasitism in a beef cow/
calf herd in Minnesota. Am J Vet. Res. 52: 1712-1716.
3Morley FH, Donald AD. Farm management and systems of helminth control. Vet Parasitol. 1980;6:105-134.
4Brunsdon RV. Principles of helminth control. Vet Parasitol. 1980;6:185-215.