In the recent months I have been asked fairly regularly for my recommendations for deworming. For most horses where their stall or paddock is picked daily, deworming every 3 – 4 months, rotating between medication types works well. These horses are exposed to less intestinal parasites compared to pastured horses, and tend to build up lower levels.
Rotating between Fenbendazole (Panacur, Safe guard), Pyrantel (Strongid), and an Ivermectin + Praziquantal (Equimax, Tapecare Plus, Zymectrin gold) helps reduce the risk of parasite resistance to any one particular medication. For pastured horse, deworming every 2-3 months is more appropriate as they tend to accumulate larger quantities and are exposed to a larger number of intestinal parasities.
Generally I recommend the Ivermectin + Praziquantal in January and July. You can then use either a Fenbendazole or Pyrantel in April and November. Every other year I recommend the use of a Panacur Power Pac to kill encysted (in the wall of the intestinal system) small strongyles, which the other medications do not kill. These take time to accumulate, so unless you have a horse showing other signs (under weight, diarrhea, poor coat, ect.), every other year is appropriate.
If you have any questions, please feel free to call or e-mail.
Clint McKnight, DVM