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<blockquote data-quote="simme" data-source="post: 1731525" data-attributes="member: 40418"><p>That is correct. The D in EPD stands for difference. Used to compare predicted differences between animals. If the BW EPD is +2, actual birth weight of a calf might be 40 pounds or 140 pounds - depending on environment. If the BW EPD is 0, then statistically the calf might be 38 pounds to 138 pounds. Extreme numbers picked for illustration. Actuals are determined by a lot more than genetics - environment, management, health. EPD's attempt to predict the genetic contribution based on observed (measured) data from lots of calves. Based on my example birth weights, you could say that it is worthless. You can have a 40 pound calf. You can have a 140 pound calf. But those are rare. If there were no EPD's and you had a bull that sired very large calves and pulled half of them at the same time that you had another bull that sired smaller calves that were not assisted at birth, you would probably decide to not use the first bull again - based on your observations. EPD's attempt to provide that decision making data in a number - based on what has been seen/measured.</p><p></p><p>Every EPD has a predicted accuracy - based on the quantity of data/measurement points that were available to predict the number. If the accuracy is low, don't trust the number as much. If the fuel gauge on your truck had a 20% accuracy, how would you use the data in deciding when to fill the tank? Yearling bulls usually have EPD accuracies around 20%.</p></blockquote><p></p>
[QUOTE="simme, post: 1731525, member: 40418"] That is correct. The D in EPD stands for difference. Used to compare predicted differences between animals. If the BW EPD is +2, actual birth weight of a calf might be 40 pounds or 140 pounds - depending on environment. If the BW EPD is 0, then statistically the calf might be 38 pounds to 138 pounds. Extreme numbers picked for illustration. Actuals are determined by a lot more than genetics - environment, management, health. EPD's attempt to predict the genetic contribution based on observed (measured) data from lots of calves. Based on my example birth weights, you could say that it is worthless. You can have a 40 pound calf. You can have a 140 pound calf. But those are rare. If there were no EPD's and you had a bull that sired very large calves and pulled half of them at the same time that you had another bull that sired smaller calves that were not assisted at birth, you would probably decide to not use the first bull again - based on your observations. EPD's attempt to provide that decision making data in a number - based on what has been seen/measured. Every EPD has a predicted accuracy - based on the quantity of data/measurement points that were available to predict the number. If the accuracy is low, don't trust the number as much. If the fuel gauge on your truck had a 20% accuracy, how would you use the data in deciding when to fill the tank? Yearling bulls usually have EPD accuracies around 20%. [/QUOTE]
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