I saw this on the Maine site and thought it was a good explanation as to why, if you're only reporting the "good" calves in your herd, you're shooting yourself in the foot.
"A huge mistake that is made by breeders when they only report their "good ones." EPDs are derived from animal’s adjusted performance record difference from contemporary group average. Estimation of the contemporary group average from the data reported is critical. For example, if I only report the "good ones" in the same group, by definition of average, half will have adjusted records above the average of the animal’s reported and half will be below “average.” Keep in mind this is the “average” of the “good ones.” Relative to the whole contemporary group, the average of the “good ones” is higher. If I take the same set of “good ones” and include the rest of the contemporary group (all calves) then the adjusted records of all of the “good ones” will be above the contemporary group average, in ratio terms, above 100. Breeders are doing a disservice to their good calves, their dams and sires, and the broader genetic evaluation system when not reporting a full contemporary group."
http://www.maine-anjou.org/hq.html
"A huge mistake that is made by breeders when they only report their "good ones." EPDs are derived from animal’s adjusted performance record difference from contemporary group average. Estimation of the contemporary group average from the data reported is critical. For example, if I only report the "good ones" in the same group, by definition of average, half will have adjusted records above the average of the animal’s reported and half will be below “average.” Keep in mind this is the “average” of the “good ones.” Relative to the whole contemporary group, the average of the “good ones” is higher. If I take the same set of “good ones” and include the rest of the contemporary group (all calves) then the adjusted records of all of the “good ones” will be above the contemporary group average, in ratio terms, above 100. Breeders are doing a disservice to their good calves, their dams and sires, and the broader genetic evaluation system when not reporting a full contemporary group."
http://www.maine-anjou.org/hq.html
