1. 2002 ADSA 2002 (GRW-1) (abstract 125) G.R. WIGGANS,* P.M. V AN RADEN, and J.C. PHILPOT Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, MD 20705-2350, USA wiggans@aipl.arsusda.gov 301-504-8334 Detection and adjustment of abnormal test-day yields

2. 2002 ADSA 2002 (GRW-2) Estimation of lactation yields Inclusion of abnormal yields may reduce accuracy Cow may be reported as sick on test day ICAR procedures exclude sick tests below a threshold

3. 2002 ADSA 2002 (GRW-3) Calculation of lactation records Best prediction used since February 1999 for calvings during 1997 or later All sick tests have been excluded: Many sick tests with milk yields >45 kg Sick coding varies by herd and dairy records processing center No check for abnormally high test-day yield compared with cow's other test days

4. 2002 ADSA 2002 (GRW-4) Objectives Check every test for abnormal yield (not just those coded as sick) Detect abnormally high or low test yields by comparison with yield from adjacent test days Define approximately 1% of each tail of the distribution as abnormal Adjust test-day yield to floor or ceiling

5. 2002 ADSA 2002 (GRW-5) Methods Calculate predicted yield Compare test-day yield with thresholds Upper: 150% of predicted yield Lower: 60% of predicted yield If test-day yield detected to be abnormal, recalculate predicted yield based on yield from adjacent test days

6. 2002 ADSA 2002 (GRW-6) Methods (continued) If test-day yield still detected to be abnormal, adjust to threshold Calculate lactation yields using best prediction with adjusted test-day yields

7. 2002 ADSA 2002 (GRW-7) For second test day and later: predicted yield = previous yield + slope (interval) Predicted yield calculation For first test day: predicted yield = following yield – slope (interval)

8. 2002 ADSA 2002 (GRW-8) Predicted yield calculation (continued) Slope is function of DIM, DIM 2, test-day yield, and interaction Coefficients differ by Test day (first vs. second and later) Trait (milk, fat, protein) Parity (1, 2, 3+) DIM group (5-49, 50+) to account for peak yield Previously identified abnormal yields not used Sick tests with milk yields of <4.5 kg ignored

9. 2002 ADSA 2002 (GRW-9) Abnormal yield detected Predicted yield recalculated by interpolating between adjacent test days If test-day yield still detected as abnormal, predicted yield recalculated again using second test day after outlier Herd average used when only 2 test days available

10. 2002 ADSA 2002 (GRW-10) Component percentage limits Detection of abnormal fat and protein yields based on weight (not percentage) Unlikely component percentages possible Component percentage limits: Fat: 2-7% and herd mean – 1% to herd mean + 2% Protein: 2-5% and herd mean – 1% to herd mean + 1.5%

11. 2002 ADSA 2002 (GRW-11) Outlier results Calvings during 1997 or later Among >93 million test-day records, abnormal yields found: Milk: 1.8% Fat: 3.4% Protein: 1.9%

12. 2002 ADSA 2002 (GRW-12) Improved accuracy? Correlations of lactations with 1 adjusted outlier with following lactation: Adjustment of abnormal yields should increase similarity between consecutive lactations Trait Lactations (no). No outlier adjustment Outlier adjustment Milk561,0630.6920.693 Fat951,3870.6530.660 Protein488,6530.6860.694

13. 2002 ADSA 2002 (GRW-13) August 2002 implementation Lactation records for calvings during 1997 or later recalculated Adjusted yields shown on industry web queries of test-day data Additional data may cause change in status of detected outlier and adjusted yield

14. 2002 ADSA 2002 (GRW-14) All test-day yields evaluated as potential outliers (not just sick tests) Improved accuracy in estimation of expected yield Floor or ceiling (instead of deletion) for abnormal yields to reflect actual yield better Improved correlation between consecutive lactations with outlier adjustment Summary