Heritage Shorthorns and EPDs

HSS continues to receive questions about the American Shorthorn Association (ASA) EPD (Expected Progeny Differences) values for Heritage Shorthorns.

Many HS (Heritage Shorthorns) breeders have looked at different websites and observed that the EPDs listed do not seem to match the known information about particular Heritage Shorthorn bulls. A couple of examples are warranted:

The ASA birth weight EPD for Mandalong Super Elephant (mature weight over 2700#) indicates he will decrease birth weight in his offspring when in actuality most of his offspring weigh well over 100# at birth.

The EPD for milk listed for Meadowbrook Chieftain 9th shows him to be in the bottom 1%, when in reality his dam had milk records over 16,000 #/year in the 1960’s, which was a phenomenal record at that time. Chieftain 9th daughters are consistently excellent dual purpose milk cows.

The are several reasons why the EPDs for HS are inaccurate.

No data was ever collected on the offspring of these old Heritage Shorthorn bulls so every EPD is a computer generated “guestimate” with no basis in hard data. HSS advises members to look at the “ACC” numbers of EPDs. ACC refers to the expected accuracy of a value, so ACC 0.20 means only a 20% chance that the EPD is “accurate”. Most Heritage Shorthorns have extremely low ACC values, meaning even ASA admits that, in many cases, their EPDs may only have a 1-9% chance that it’s an accurate number. Another important factor is simply the heritability of genetic traits which is often very low—10-20%. When the ACC number is combined with the heritability of a genetic trait there may only be a 1-2% chance that the EPDs is truly factual which explains why phenotypical observations rarely equal the EPD expectations.

Another problem is that ASA Shorthorn EPDs are regularly “tweaked” to fit changing computer models with no explanation as to the whys and wherefores. Public information regarding the individuals making these decisions does not seem to be available. This promulgates a mistrust in EPDs that ASA has had to address because of concerns about accuracy and bias even in the Modern Shorthorns owned by ASA’s members. Many believe that the EPDs of Heritage Shorthorns have been purposely discriminated against in comparison to Modern Shorthorns.

In conclusion, HSS cautions all breeders and purchasers of Heritage Shorthorns to be very skeptical of EPDs, and to make their own decisions about EPD reliability for particular Shorthorns.