Fecal egg counts (FEC) is a great tool but you need to use it right. One single egg count on an individual animal is not very useful but when you have samples on all the animals in a group that are managed the same way on the same pasture it becomes an excellent tool to distinguish the good from the bad.
FEC are measured in number of eggs per gram of fecal sample. The most common method mixes 2g of fecal matter with 28 grams of flotation solution, add a small amount of this solution to a special slide with a grid and look at that under the microscope to count the number of eggs seen. This number is then multiplied by 50 to come up with a number of eggs per gram (epg). The difference between a FEC of 50 epg and 100 epg is basically only one egg and therefore not really much of a difference.
To get the most out of your FEC results the average FEC for the group of sheep that you are looking at should be at least 500 epg and your results are even better if you can get to 1000 epg average.
The black ram lamb in the second picture has a FEC of 0 epg and the brown and white ewe lamb has 6100 epg, She does have a FAMACHA score of 3 but other than that you would not guess that she had worms.
We collected fecal samples on 125 lambs and here are the results:
The average for the group was 925 epg
We had 3 lambs with 0 epg at the low end and a lamb with 6100 epg at the high end
85 lambs (51 ewe lambs and 34 ram lambs) had FEC below the average for the group (what you want) while 48 lambs had above average FEC (what you don't want)
What are we going to do with these results?
1. The 48 lambs with above average FEC (male and female) are going to pursue a career as delicious lamb
We are going to do another FEC on all the lambs in 4 weeks for even better accuracy and then,
2. We are going to see how the three rams that we used to sire these lambs compare to each other as far as passing parasite resistance on to their offspring. We will use this to decide who we are using for breeding in the fall.
3. We are going to use FEC results of their lambs as part of our decision making process on which of our ewes to keep or cull
4. We are going to select our replacement ewe lambs out of the 51 ewe lambs with below average FEC results
5. We are going to select the ram lambs we have for sale out of the 34 ram lambs with below average FEC results
So, how did the rams do so far?
WHK 1352 (Midnight)
79% of his lambs had FEC below 925
72 lambs
695 epg average for just his offspring
Lowest 0 epg
Highest 6100 epg
OHK 51 (Mister)
51% of his lambs had FEC below 925
29 lambs
1470 epg average for just his offspring
Lowest 50 epg
Highest 6050 epg
GBR 1609 (Ram-Ram)
67 % of his lambs had FEC below 925
21 lambs
980 epg average for just his offspring
Lowest 50 epg
Highest 4800 epg