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How Does Additional Information Impact Accuracy?

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?

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  1. How DoesAdditional InformationImpact Accuracy? Dan W. Moser Department of Animal Sciences and Industry Kansas State University, Manhattan http://www.asi.ksu.edu

  2. 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?

  3. What Drives Genetic Change? Bourdon, 2000

  4. What Drives Genetic Change? • Accuracy of Selection • Generation Interval • Genetic Variation • Intensity of Selection

  5. 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

  6. 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?

  7. 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

  8. Correlated Traits

  9. 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

  10. Accuracy of Correlated Selection Acc (ERT selection) = Acc (Indicator EPD) x rG btw ERT and Indicator Where Acc is true accuracy, not BIF accuracy

  11. 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?

  12. 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:

  13. BIF Accuracy

  14. 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

  15. 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

  16. 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

  17. Progeny Test Example

  18. Progeny Test Example • Progeny data add accuracy, regardless of heritability • Pedigree adds relatively little accuracy especially when significant numbers of progeny are evaluated

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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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