Jared Decker, PhD University of Missouri One point must be clear from the very beginning: EPDs work. When we select parents based on EPDs the genetic merit
for that trait increases in our herd. When we select the parents using EPDs the
performance of the next generation improves. EPDs
Defined EPD stands for Expected Progeny Difference. These three words are loaded
with meaning, thus the need to define them here. The most loaded word is
Expected. Here we use Expected the way a statistician would use the word.
Expected means we are making a prediction of a future value. But, in this
context, Expected also means we are describing the average of a group. What is
the group for which we are predicting the average? We are predicting the
average performance of the Progeny or calves out of an animal. An animal’s own
performance and its EPD can be quite different, because that is not the purpose
of an EPD. The EPD is predicting the average performance of that animal’s calf
crop. Finally, EPDs are u…
You are asking yourself, who is Reverend Bayes and what does he have to do with cattle? The answer to this question will answer a major misconception in cattle genetics.
Reverend Bayes was an 18th century Presbyterian minister. He was also trained in logic. Due to Bayes’ work on probabilities, an approach to statistics called Bayesian statistics is named after him. In Bayesian statistics, we start with a prior belief (prior probability). As more information and data are gathered, we update this prior belief. We call this new update a posterior belief. We continue this process as we collect additional data. Further, a key tenant of Bayesian statistics is evaluating the methods (i.e. models) used in our analysis. Statisticians and scientists did not frequently use this system of statistics in the early 20th century. But, with increased computing power, Bayesian statistics has become very popular in the 21st century.
Cattle genetic prediction is very much Bayesian. We start with a prior…
We see things through the lens of our expectations.
What if the t is a threat? What if you didn't even see it? What if the t is an opportunity? It is a lot easier to see threats and opportunities at your neighbor's operation.
Too often, we wait till we are out of time and money to make changes.
We hear the phrase, "If you always do what you have always done you will always get what you've always got." But, in the cattle business…