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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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