For decades, horse owners were taught to rotate different deworming chemicals every 8 weeks. Today, the American Association of Equine Practitioners (AAEP) strictly warns against this practice. Rotational deworming has caused widespread parasite resistance, making some chemicals completely useless.
The Problem with Rotational Deworming
By deworming every horse on a rigid schedule, we kill off the weak parasites and leave the resistant 'super-worms' to reproduce. Modern veterinary science advocates for Strategic, Targeted Deworming, focusing on individual horse susceptibility.
The 80/20 Rule of Equine Parasites
In any pasture, approximately 20% of the horses carry 80% of the parasite load. These horses are 'high shedders'. The remaining 80% of horses are naturally resistant and need minimal chemical treatment.
How to Implement Strategic Deworming
1. Perform a Fecal Egg Count (FEC): Have your vet analyze a fresh manure sample twice a year (spring and fall). 2. Classify Your Horse: * Low Shedder (0 - 200 eggs per gram): Needs deworming only twice a year (typically Spring and Fall) targeting tapeworms and strongyles. * Medium Shedder (200 - 500 eggs per gram): Needs 2 to 3 targeted treatments per year. * High Shedder (500+ eggs per gram): Requires 4 treatments per year and pasture management reviews. 3. Pasture Management: Pick up manure from paddocks twice weekly and do not overstock pastures. This naturally breaks the parasite life cycle without chemicals.