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How Does Additional Information Impact Accuracy?. Dan W. Moser Department of Animal Sciences and Industry Kansas State University, Manhattan http://www.asi.ksu.edu. Additional Information. Start with a pedigree, possibly a phenotype Add: Phenotype for a correlated indicator trait

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how does additional information impact accuracy

How DoesAdditional InformationImpact Accuracy?

Dan W. Moser

Department of Animal Sciences and Industry

Kansas State University, Manhattan

http://www.asi.ksu.edu

additional information
Additional Information
  • Start with a pedigree, possibly a phenotype
  • Add:
    • Phenotype for a correlated indicator trait
    • Progeny test data
    • DNA test results
  • How much is accuracy of selection increased by adding each piece of additional information?
what drives genetic change1
What Drives Genetic Change?
  • Accuracy of Selection
  • Generation Interval
  • Genetic Variation
  • Intensity of Selection
rate of genetic change
Rate of Genetic Change
  • Additional information
    • Should increase accuracy
    • May increase generation interval
    • May reduce intensity of selection
      • If only certain animals have additional info
it often comes down to
It Often Comes Down To:
  • Is the value of the additional information worth the time and cost required to get it?
  • Is the additional information available on enough animals to maintain selection intensity?
correlated traits
Correlated Traits
  • Birth Weight as a predictor of Calving Ease
    • Because Calving Ease is a binary trait (yes/no), having a correlated continuous indicator trait can add considerable accuracy to selection
unmeasured ert
Unmeasured ERT
  • ERT = Economically relevant trait
  • When ERT is unmeasured, the genetic relationship between the ERT and the indicator trait must be strong
  • Otherwise accuracy of selection for the ERT using only the indicator is low
accuracy of correlated selection
Accuracy of Correlated Selection

Acc (ERT selection) = Acc (Indicator EPD)

x rG btw ERT and Indicator

Where Acc is true accuracy,

not BIF accuracy

example ultrasound
Example: Ultrasound
  • Use live-animal ultrasound measurement as an indicator of carcass merit
  • Assume genetic correlation btw yearling bull ultrasound and steer carcass is 0.70
  • If a bull has an ultrasound EPD with accuracy of 0.90, what is the accuracy of selection for carcass?
example ultrasound1
Example: Ultrasound

If the 0.90 accuracy is “true” accuracy, then the “true” accuracy of selection is:

0.90 x 0.70 = 0.63

But “BIF” accuracy would be quite different:

bottom line
Bottom Line
  • BIF accuracy understates the true accuracy of selection
  • Selection on indicator traits only is significantly less accurate unless the genetic correlation is very high
progeny test
Progeny Test
  • How much additional accuracy is added by a progeny test, assuming the animal is phenotyped?
    • Depends on the heritability of the trait
    • Depends on the number of progeny
    • Depends (a little) on how much pedigree information is available on the animal
progeny test example
Progeny Test Example
  • BIF accuracy values, calculated from Selection Index
  • Individual record on animal
  • 10 or 200 Paternal half-sibs
  • 0, 5, 50 or 500 progeny
  • Heritability of 0.05, 0.25 or 0.45
progeny test example2
Progeny Test Example
  • Progeny data add accuracy, regardless of heritability
  • Pedigree adds relatively little accuracy especially when significant numbers of progeny are evaluated
adding molecular information
Adding Molecular Information
  • Van Eenennaam (2010) showed that if molecular breeding values (MBV) explained all of the genetic variation for a trait, the increase in genetic gain from MAS would be substantial
  • No products currently on the market have been shown to explain a majority of the variation for a quantitative trait
adding molecular information1
Adding Molecular Information
  • MacNeil et al. (2010) compared the use of ultrasound measurements and MBV for prediction of carcass marbling BV in Angus cattle
  • Genetic correlation between ultrasound IMF and carcass marbling was 0.56, and 0.38 between MBV and carcass marbling
adding molecular information2
Adding Molecular Information
  • Despite the lower genetic correlation, the authors expected greater genetic gain from selection on MBV than on ultrasound, because MBV are fully heritable
  • Ultrasound values on sibs provide significantly increased genetic gain, but MBV on sibs does not
adding molecular information3
Adding Molecular Information
  • Authors concluded that a very limited amount of progeny carcass data would be more informative than either MBV or ultrasound
  • MBV selection is more useful for traits that are difficult to measure, or that are measured later in life
summary
Summary
  • Accuracy of indicator trait EPD does not reflect accuracy of selection for ERT
  • Progeny records add significant information, but adds both expense and time to evaluations
  • Molecular breeding values could be a very useful tool for selection, if the tests explain larger portions of the variation in a trait.
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