Since cows, bulls and young stock are affected differently by internal parasites, corresponding treatment programs should also differ. Table 3 gives a recommended guideline for deworming beef cattle.
Mature cows should be treated at least one time per year. The best time to treat the mature cow is near freshening. The mature cow’s susceptibility to parasite detriment increases during this time due to stress of production and a suppressed immune system. In situations where parasite levels may be high, such as overstocked pastures, treating twice a year may be necessary. In other situations, parasite levels may be low enough that mature cows do not need any treatment. These conditions can only be determined by treatment followed by critical observation. Bulls, unlike cows, tend to be more susceptible to parasites and should be treated twice a year, spring and fall. Since mature cows and bulls have some degree of acquired immunity to internal parasites, the older benzimidazole-type products should do a sufficient job of controlling parasites in these animals.
Treatment of calves should begin when they reach three to four months of age and again at weaning if they are kept as replacements or stockers. The avermectin/milbemycin-type products will provide the best means of controlling parasites in these animals. Treating calves every three to four months may be necessary to optimize parasite control until the calves become yearlings. Yearlings can be treated on a seasonal basis, spring and fall, until they are mature cows (a mature cow is generally recognized as an animal pregnant with her second calf). If calves are backgrounded in a drylot, one initial treatment should be sufficient.
Visit a local veterinarian about setting up a herd health program that includes a strategic deworming program.
Source: Shane Gadberry, Extension Livestock Specialist Jodie Pennington Extension Dairy Specialist Jeremy Powell, DVM Extension Veterinarian