The Fecal Egg Count
By Eleanor Blazer

      Ever had a colonoscopy? 

       It is a test doctors advise we have regularly after age 50 to detect polyps and cancer within the colon.  Preparation for the test is not pleasant.

      There is a test horses should have twice a year - the FEC.  It's not unpleasant, for the horse. 

      Horses are lucky - all they have to do is donate one or two lumps of manure for the fecal egg count (FEC) test.   They don't have to fast, drink laxatives, run to the bathroom every few minutes and then have someone stick a probe up their bottom.  They do need their owners to collect the specimen and take it to the vet for the test.

      At the lab, a technician mixes the manure with solution.  The worm eggs float to the top.  A gram of the specimen is examined under a strong microscope and the eggs per gram are counted. 

     Most labs just count small strongyles.  Large stronglyles, in all stages, are easily controlled.  If the small strongyle population is controlled then so goes the large.  If a horse has a high population of small strongyles, he generally also has ascarids.

     Using the FEC to detect tapeworms is not reliable.  Tapeworms infrequently shed segments which may contain eggs (needed for detection).  In comparison, other intestinal worms shed eggs almost continuously.

      The lab will report the small strongyle egg count as eggs per gram.  The FEC scale is: less than 150 eggs per gram - low; 151-399 eggs per gram - medium; 400 plus - high.

      Horses with a FEC of 200 or more are candidates for colic, unthriftiness and anemia.  These horses are also contaminating the pasture and keeping the parasite growth cycle active.

       Conducting a second fecal egg count 14 days after a dewormer has been administered will tell you if the product worked.  A low fecal egg count reduction (FECR) can indicate parasite resistance to the active ingredients in the product.  A low count may also indicate the product was old or not enough administered.  The horse should be dewormed with a product that uses a different chemical class as the active ingredient.  Then another FEC conducted within 10 - 14 days.

      Horses with a steady fecal egg count of less than 150 eggs per gram may only need to be dewormed twice a year.  Deworming horses that do not need to be aggressively dewormed is expensive and can create resistance to dewormer ingredients.

      Many vet clinics will do a fecal test to detect worms, but not count the eggs per gram.  In order for the test to be beneficial you must request a count.

      Equine Studies Institute recently purchased a project horse from auction.  His initial FEC result was 650 eggs per gram.  Watch "Red's" progress at  His follow up test can be seen on the blog.

      Drop off a sample of your horse's manure at the vet clinic - it's easy.  A lot easier than a colonoscopy!

        Proper nutrition and management practices can prevent many problems associated with caring for horses.  You can learn how to provide your horse with a better life-style by taking the online course "How to Feed for Maximum Performance" taught by Eleanor Richards Blazer.

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