Feed Lot

JUN 2018

Feedlots and cow/calf operations in the beef industry who feed 500 or more has annually on grains and concentrates; maintain 500 or more beef cows; backgrounder, stocker/grower, preconditioner; veterinarian, nutritionist, consultant

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FEED•LOT June 2018 9 By targeting certain animals in the herd not all parasites will be killed, so resistant parasites are diluted with susceptible ones, di- luting the resistant gene pool. The concept is called refugia. Another option to consider is using a combination of products, Ensley said. Pairing a white de- worming drench with an injectable or pour on can drive up efficacy. "If only 1% of parasites survive a combination deworming strategy, it is much easier to dilute that 1% of resistant organisms. You knock down the percentage of resistant parasites that way," he explained. Accurate dosing is another important consideration. Under dosing increases the chance of parasites not succumbing to the deworming product, thus strength- ening their resistance. Knowing the challenge the sheep industry faces with parasite resis- tance, Ensley said it's time to look at deworming from a different perspective. "We need to think about the parasites themselves. Are we treating cattle in a way that is building resistance?" he asked. "Or are we using a plan that extends the life of the products we have. "What used to be the best plan might not be so great, any more." FL Although cattlemen might not want to get a lecture from a sheep herder, there is one topic that ranchers better take note of from the sheep industry – parasite resis- tance. The issue is well document- ed. And with no new parasiticides for cattle in the pipeline, Doug Ensley, DVM, technical marketing manager for cattle, Boehringer Ingelheim, said it's time for cattle- men to change our way of thinking when it comes to deworming. Years ago, it was standard prac- tice to deworm all livestock every spring, and often again in the fall. But Ensley said instead of deworm- ing by the calendar, deworm ac- cording to the needs of your herd. "For the last 35 -plus years, we've been deworming with many of the same general products. So we need to develop a plan to use those products in a way that will give us the benefits of deworming in the future," he said. By deworming all animals, we are exposing all parasites to the parasiticide, and if the parasites live, they will reproduce other parasites that are also resistant, thus strengthening the number of resistant organisms. "I recommend working with your vet to develop a program, and then monitor the program to see how well it is working," Ensley said. Often cattlemen don't consult their veterinarian on a deworming strategy, but a vet has some tools in his toolbox that can benefit a deworming program and limit par- asite resistance. Ensley suggested thinking about a different approach to deworming. One such strategy is not deworming the entire herd. Instead consider what animals are at greatest risk of parasites, like young animals and young breeding stock. "Those are the most susceptible to parasites, so maybe focus on those animals as you move forward. Older animals have had exposure to parasites and most likely have some resistance." Monitoring fecal egg counts can also help identify those animals with a parasite problem. "Typically 20% of the animals have 80% of the parasites. Those are the ones to target with a parasite control pro- gram," he recommended. PEST AND PARASITE CONTROL Take a lesson from sheep when it comes to resistant parasites. BY JILL J. DUNKEL Are Ewe Listening?

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