By Nora Grenager, VMD, DACVIM
Timing of Manure Collection
It is important to take a sample when the efficacy of any previous dewormer is out of the system. Dewormer drugs have different durations of efficacy. So, if the last dewormer used was:
ivermectin: wait 12 weeks
moxidectin: wait 16 weeks
pyrantel salts: wait 8 weeks
fenbendazole or oxibendazole: wait 8 weeks
If this is the first time a FEC has been performed on the horse, discuss with your veterinarian about whether to do a FEC Reduction Test to evaluate if your horse has any parasite resistance to each type of dewormer. The FECRT involves: a FEC at day 0 (an appropriate amount of time after the last dewormer*), administering a dewormer per package recommendations, then a second FEC at day 10-14. This would need to be done for each type of dewormer, if necessary.
The first FEC is best done in the spring or fall, not in the heat of summer when there are typically fewer parasites.
How to Get the Best Manure Sample
Fresh manure is important, as eggs deteriorate with time and temperature. Ideally, collect the sample immediately after your horse has passed it. If you are not sure, but a pile looks fresh, collect sample from the middle of the pile where it is still moist.
Collect a large handful of manure in a ziplock bag then push as much air out of the bag as possible before sealing it.
Bring the sample to the clinic as soon as possible, certainly within 24 hours.
Keep the sample refrigerated until you drop it off at the clinic. Room temperature is fine if you are bringing the sample right away. Do not put it in direct sunlight or store it in a hot car.
Drop manure off during regular business hour Monday through Friday; earlier in the day is better so the sample is sure to be run the same day.