Cow/calf producers may have thought they were out of the
woods on this one, but research in the U.S. and a bit in Canada is showing that
the single pour-on/ivomec-type treatment may no longer being effective in controlling
Just like grain and oilseed growers who are running into
problems with herbicide resistant weeds, the beef industry is now facing the
cold hard fact, that repeat use of a single long-effective product is producing
parasites in the gut of beef cattle that are immune to the treatment.
I won’t go into all the reasons why here – more on that
later – but the U.S. is finding widespread resistance in cattle there, and
unless you believe bugs suddenly change their behavior once they hit the 49th
Parallel, it is suspected the same is happening here in Canada.
Basically too much of one good thing, has allowed certain
parasites with resistance to go forth and multiply. Solutions include change in
management – looking at timing of treatments, looking at pasture management to
minimize the parasite load on pastures – and also about using a combination of
products with different modes of action to control these parasites.
As they are finding in dealing with herbicide resistant
weeds, using two products with different modes of action at the same time,
appears to be much more effective in controlling weeds than simply using single
products on different years….it is a similar finding in parasite control. Two
products at once are more effective than rotating products.
I was just at a conference organized by the University of
Calgary Veterinary Medicine school, and the issue of parasite resistance was
one of the topics. There didn’t seem to be a lot of information on the
economics of parasite control, but I am sure that will come.
Overall the points speakers were making: 1. Be aware that
parasite resistance is out there; 2. Look at management practices to help
reduce the parasite load on pastures; 3. The biggest bang for the buck in dealing with parasite resistance is at the cow/calf, backgrounding level, and not at the finishing feedlot. 4. Consult with your veterinarian on
product options to provide the best level of control.
These guys bought me lunch, so I am bound by law to write
more about this later.
Lee Hart is editor of Cattleman’s Corner based in
Calgary. Contact him at 403-592-1964 or by email at [email protected]
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