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Update on the Test-Day Model. Test-Day Model. Data includes individual cow milk weights and component percentages recorded on test day

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test day model
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
test day model continued
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
test day model continued4
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
test day data
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
test day data continued
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
test day data continued7
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
detecting outlier lactation records
Detecting Outlier Lactation Records
  • Some herds have high percentage of "elite" cows
  • Investigation showed abnormal distributions for lactations from those herds
outliers continued
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