Monday, July 8, 2013

Rising fecal egg counts

As expected, fecal egg counts are rising. For the samples collected on June 27, fecal egg counts ranged from 0 to 6,900 epg and averaged 1,120 +1,132 epg. The median egg count was 890 epg. There was also considerably more variability in egg counts, as evidenced by the larger standard deviation.

However, only 15 percent of the goats (n=11) had fecal egg counts above 2,000 epg, the usual cut-off point for Bronze-qualifying bucks. The barber pole worm (Haemonchus contortus) is a very prolific egg layer. 2,000 epg is considered to be of clinical significance, though clinical parasitism can occur with lower egg counts and vice versa.

In the history of the test, fecal egg counts and FAMACHA scores have usually been positively correlated, but not very strongly. For this reason, a fecal egg count is not a good diagnostic test for an individual goat, unless there is other supporting data (e.g. FAMACHA score or packed cell volume).

Over 57 percent of the goats (n=42) had fecal egg counts below 1,000 epg. Over 31 had egg counts below 500 epg. One goat (#323, Burke) had a negative fecal egg count (epg=0), compared to 55 negative fecal tests on June 13. All of the bucks consigned by Kendell and Dana Barnes (KY) had low egg counts (< 500 epg) on June 27.

The 80:20 (or 70:30) rule states that only 20 percent of the herd is responsible for depositing 80 percent of the worm eggs onto pasture. By identifying and eliminating the heavy egg shedders, it is possible to reduce the level of pasture contamination. Selecting a buck with consistently low egg counts is one of the best ways to reduce the level of pasture contamination, as more of his offspring will be resistant (shed fewer eggs), compared to the offspring of a susceptible buck.

Download June 27 FEC report