Update on the TestDay Model - PowerPoint PPT Presentation

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Update on the TestDay Model

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Genetic evaluations based on test-day (instead of lactation) data can account ... and several European countries; Australia has used a test-day model since 1985 ... – PowerPoint PPT presentation

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Title: Update on the TestDay Model


1
Update on theTest-Day Model
2
Test-Day Model
  • Data includes individual cow milk weights and
    component percentages recorded on test day
  • Genetic evaluations based on test-day (instead of
    lactation) data can account for environmental
    influences more accurately and for genetic
    differences in shape of the lactation curve

3
Test-Day Model continued
  • Used in Canada and several European countries
    Australia has used a test-day model since 1985
  • Cornell Foundation granted patent in 1993, which
    has prevented the U.S. from implementing a
    test-day model 2000 re-examination upheld the
    patent

4
Test-Day Model continued
  • Canadian Dairy Network requested re-examination
    of patent in Canada expects to learn if patent
    was upheld during 2002
  • Several European groups are collecting
    information to show that patent should not be
    upheld in Europe

5
Test-Day Data
  • Received at least weekly from regional computing
    centers
  • Includes information from nearly 30 million
    lactations from calvings since 1990
  • Many checks to ensure data integrity

6
Test-Day Data continued
  • Lactation records calculated using best
    prediction
  • Upper and lower limits imposed
  • 60-150 of expected yield derived from preceding
    or adjoining normal test days
  • Floor and ceiling used
  • 1-2 of test-day yields affected
  • Test-days weighted according to correlation with
    305-day yield
  • Weights affected by closeness to other test days

7
Test-Day Data continued
  • Recent changes
  • Minimum days in milk decreased to 5
  • Specific reporting of lactations that start with
    an abortion or reasons other than a normal calving

8
Detecting Outlier Lactation Records
  • Some herds have high percentage of "elite" cows
  • Investigation showed abnormal distributions for
    lactations from those herds

9
Outliers continued
  • Possible solution
  • Develop criteria based on normality statistics to
    detect herds with outlier lactation records
  • Adjust weight that records receive based on
    departure from normality
  • For extreme cases, cow's own records would have
    little influence on her evaluation
  • Determine if reduced weight for extreme records
    improves accuracy of parent average in predicting
    future progeny performance
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