CALF_News_April_May_2021

34 CALF News • April | May 2021 • www.calfnews.net PARASITE RESISTANCE TO CATTLE DEWORMERS enables the production-robbing pests to punish production by disrupting breeding, lowering cow and calf immune systems and reducing weaning weights and overall gain. But by following the “four pillars of sustainable deworm- ing,” producers can better manage and control parasites before they damage herd performance. D.L. Step, DVM, professional services veterinarian for Boehringer Ingelheim, says the four pillars are: diagnostics , treatments , refugia and management . Step was among veterinarians and beef cattle specialists who took part in a recent animal health management seminar presented virtually by Boehringer Ingelheim. “These pillars should be followed to maximize productivity of average daily gain and to produce a profitable weight gain,” Step pointed out. Cattle dewormers, or anthelmintics, have long been essen- tials in parasite control programs. But resistance to deworm- ers – due primarily to depending too heavily on one type of anthelmintic – has caused veterinarians, other animal health experts and producers to rethink parasite control. Dewormers come in two classes. One is macrocyclic lac- tones, or endectocides. Endectocides (either injectables or pour-ons) include ivermectin, doramectin, eprinomectin and moxidectin, with trade names Ivomec®, Eprinex®, Dectomax®, Cydectin® and LongRange®. They provide internal and external parasite control, and control typically lasts longer. The second class is benzimidazoles, or white wormers. White wormers (drenches) include oxfendazole, fenbendazole or albendazole, with trade names Valbazen®, Synanthic®, Safe- Promote Better Parasite Management Four Pillars of Sustainable Deworking Guard® or Penacur®. An oral dose has a rapid effect. It only controls internal parasites and its efficacy is typically no longer than two days, Step indicated. Step said about 78 percent of deworming doses are in the endectocides class, with 40 percent of those from a generic ivermectin pour-on. The remaining 22 percent of deworming doses are from white wormers. By using the following four pillars of sustainable deworming, producers can determine which dewormer combination may work best for a particular production environment: Diagnostics – This pillar involves monitoring dewormer efficacy with ongoing surveillance and routine diagnostic testing. The fecal egg count reduction test (FECRT) is used to compare parasite egg counts in feces before an anthelmin- tic treatment and 10 to 14 days afterward. If there is weak response to treatment from either an endectocide or white wormer, then the efficacy of product brands within the same class of drugs are also likely weak. Treatments – To increase efficacy, consider a combina- tion treatment using multiple dewormer drug classes with different modes of action. In research to measure dewormer efficacy to combat gastrointestinal nematodes in livestock, Step said both endectocides and white dewormers provided 85 percent, 90 percent and 99 percent efficacy when used alone in three separate tests. But when used in combination, the 85 per- cent efficacy jumped to over 97 percent, the 90 percent efficacy increased to 99 percent and the 99 percent efficacy rose to 99.99 percent. Continued on page 37  By Larry Stalcup Contributing Editor ABOVE: Better parasite control management by using more than one type of wormer can improve breeding rates and calf immune systems, which should lead to better weaning weights and more profit potential.