Tuesday, September 3, 2013

Fecal Egg Count Data is Complicated

For the fecal samples collected on August 21, fecal egg counts ranged from 0 to 13625 epg and averaged 897 + 1913 epg, compared to 1096 + 1239 on August 8. The median was 320 epg, compared to 625 epg two weeks ago. Only six goats had egg counts above 2000 epg.

Since 2008, these have been the performance standards that have been used to determine which bucks meet Gold, Silver, or Bronze standards for parasite resistance (fecal egg counts):

As of August 21, seven bucks are meeting the Gold standard for parasite resistance:  #'s 304 and 388 (Adams, IL); #328 (Dennison, KY); #334 (Majancsik, KY); #'s339 and 343 (Murphy, NJ);and  #359 (Richhart, IN).  Four are meeting the Silver standard and 12 are meeting the Bronze standard.  So far, fifty-one (69%)  bucks have disqualifying fecal egg count data.

Two factors complicate the interpretation of this year's fecal data:  scours and deworming. It is difficult, if not impossible to obtain a fecal sample from a goat that has liquid feces. At the same time, a goat with scours is more likely to have a high egg count, as scours can be a symptom of Trichostrongylus and Teladorsagia.

Without a fecal sample, it is impossible for a goat to have a disqualifying egg count (> 2000 epg). Goats with fewer egg counts (observations) have less chance of having disqualifying egg counts.

The increased number of dewormings is also problematic. An effective deworming will reduce fecal egg count by 95 percent or more. Even a less effective treatment will cause the subsequent fecal egg count to go down. For this reason, the fecal egg count that follows a deworming is not factored into the calculation of a buck's average fecal egg count. Deworming generally does not have an effect on reinfection.

The more often a goat is dewormed, the less likely it is to have a disqualifying fecal egg count. For this reason, goats with FAMACHA© scores of 3 probably have an advantage over goats with FAMACHA© scores of 1 or 2, as 3's were usually dewormed with levamisole or moxidectin.

Consider goat #310. This buck was never dewormed. However, it has two "disqualifying" fecal egg counts (> 2000 epg) and a "disqualifying" average fecal egg count of 1408 epg. Had it been dewormed once or twice, like many goats with FAMACHA© scores of 3, it may not have had any disqualifying fecal egg count data.

It goes without saying that selection of this year's sale bucks will be more complicated than in previous years. Please contact Susan at (301) 432-2767 x343 or sschoen@umd.edu, if you have any questions about the fecal data. One more fecal egg count will need to be factored into the test results.

Download August 21 FEC Report -- updated 09.11.13