Internal Parasites ~ What to Use and When       Dewormers for cattle Generic name Brand names Route* Comments thiabendazole TBZ B, D, F, P Parasite resistance is a problem. levamisole Tramisol Ripercol Levasol Totalon B, D, I, S   ivermectin Ivomec I Very effective against roundworm larval and encysted stages and external parasites. morantel Rumatel Nematel B, F   fenbendazole Pancur   Effective against tapeworms.   Safe-Guard D, P, Salt Some effect on ecysted roundwork larvae. albendazole Valbazen D Effective against roundworms, liver fluke, and tapeworms. * Route administration:  B-bollet, D-drench, F-feed, I-injectable,    P-paste, S-skin, Salt-salt block.   1. Subclinical infections (less than 30 eggs per gram of feces). a. In several trials conducted in Montana, Oregon, and Utah, deworming cows with a broad spectrum product that kills inhibited larvae as well as immature and adult parasites has been shown to be cost-effective.  Cows dewormed in the late fall carry more weight through winter, wean heavier calves, and in some cases breed back faster than non-treated controls within the same herds. b. Individual producers in consultation with their veterinarians need to decide whether deworming cows with subclinical infections will be profitable for their operations. 2. Moderate infections a. Cows: Deworm in fall to provide maximum benefit. b. Calves: Deworm at weaning if you are keeping them or are getting paid by the buyer to do so. c. Stockers: Deworm at weaning (or aquisition) and thereafter as required or indicated by finding parasite eggs in fecal samples. 3. Heavy infections a. Cows: Deworm in fall same as above, then again in the spring.  The third deworming should be given 3 to 4 weeks later.  Third treatment may be delayed depending on product used and/or negative egg count after 4 weeks. b. Calves and Stockers: Deworm in the same pattern as cows as well as at weaning or acquisition. Note: For improved results, move cattle to a clean pasture (free of parasites) immediately after deworming.   Clell Bagley, D.V.M., Extension Veterinarian Mark C. Healey, D.V.M., Ph.D., Parisitologist ~ Utah State University Donald Hansen, D.V.M., M.P.V.M., Extension Veterinarian ~ Oregon State University