Deworming cattle can be an important management practice for cattle producers. The most appropriate deworming strategy will vary by type of operation (i.e., cow-calf, stocker, feedlot), geographic location, animal age and other factors. The following discussion will focus on considerations for cow-calf operations.
Geographic location and the associated differences in the amount of rainfall, timing of rainfall, grazing considerations, temperature and other factors have a huge impact on transmission and survival of internal parasites. These differences impact when treatments should be administered.
Transmission of parasites throughout the year varies based on location. For example, transmission in North or South Dakota might occur from May to November compared with transmission throughout the entire year for states like Texas and Oklahoma.
Transmission of internal parasites is greatly influenced by rainfall. Deworming twice a year is often appropriate for high-rainfall areas. In contrast, it may not be beneficial to treat for internal parasites at all in some low-rainfall areas.
Even within the same geographical area, timing of treatment may vary depending on the residual activity of the product being used. Ostertagia ostertagi is generally considered the most clinically important internal parasite. In much of Texas, the target window for strategic treatment of ostertagia is June or early July. If the product being used has zero residual activity against ostertagia, then treatment should occur during this target window. Products with longer residual activity could be applied earlier to better coincide with other management practices or before it gets quite as hot.
Active ingredients and how effective they are against certain species are also important in developing a successful deworming strategy. The most-used active ingredients can be classified as macrocyclic lactones or benzimidazole (aka “white dewormers”). Macrocyclic lactones include moxidectin, eprinomectin, doramectin and ivermectin. Benzimidazoles include albendazole, fenbendazole and oxfendazole. Internal parasites from the cooperia genus can be a concern in younger cattle, but these parasites are not generally important after cattle reach a year old. It is also important to know that the benzimidazoles are generally much more effective on cooperia than macrocyclic lactones.
Product efficacy and not just cost should also be considered. Unfortunately, reduced efficacy has been observed with some of the generic ivermectin products in both research and field conditions.
Working with appropriate experts in your area can help ensure a successful, cost-effective deworming strategy is developed and administered at the right time of year for your operation.
