Considerations for control of heln1inths in stocker cattle

Many factors influence the spectrum and magni tude of helminth populations in stocker cattle. Calves are placed into stocker operations during all seasons, from all regions of the country, and with a broad range of prior parasite exposure and parasiticide treatment. This makes it unlikely that a generalized or generic parasite control program will be effective for all animals at receiv ing. Follow-up treatment recommendations are equally problematic, contingent upon the success of the treat ment protocol utilized when cattle arrived at the stocker operation, residual activity of the anthelmintic(s) used at arrival, parasite challenge during the stocker phase, general animal health, and producer expectations. At the farm or ranch level, the more troublesome and conflicted considerations regarding parasite control are often ignored, and treatments are based on what appears to have worked in the past or the current cost of treatment options. This paper is not intended to make detailed recommendations about worm control, but is instead a discussion of factors at play in stocker cattle, including the species of the parasites, biology of the parasites, parasiticides, and the interaction and effect of these factors on the health and productivity of stocker cattle.