Parasitologists saw dewormer resistance in cattle coming before most producers did. But, overuse of benzimadazoles, macrocyclic lactones and levamisoles in all their forms has increased reports of nematode resistance. However, Ray Kaplan, a professor of parasitology with the College of Veterinary Medicine at the University of Georgia, says what sheep raisers have learned about resistance applies to cattle. Combining two classes of anthelmentics and administering them together is proven to reduce surviving internal parasites.
Source: DTN, September 10, 2018. Link.
Combining anthelmintics is not as simple as mixing two products together and applying them. Kaplan stresses different groups of dewormers are not chemically compatible and they can’t be missed together in the same syringe. To achieve a combination treatment, producers need to administer products separately, one immediately after the other – and at the full, recommended dose. If withdrawal times are a concern, use the longest one.
INSIGHTS: Note that sources in the article support the notion that anthelmintic use will continue. Proper dosing, sound on-farm management, including fecal egg counts and a tenacious deworming program will help ensure ongoing efficacy.