1. 2004 R.L. Powell,* A.H. Sanders, and H.D. Norman Animal Improvement Programs Laboratory Agricultural Research Service, USDA, Beltsville, MD rlpowell@aipl.arsusda.gov Accuracy and stability of national and international somatic cell score evaluations

2. ADSA-ASAS JOINT MEETING 2004 (2)R.L. Powell 2004 Objectives Investigate the accuracy and stability of somatic cell score evaluations  From US data (study one) Overall By bull sampling status ‘S’Standard sampling, defined by NAAB ‘O’Other (alternative) sampling  From Interbull data (study two) For bulls with US evaluations By inclusion of foreign daughters

3. ADSA-ASAS JOINT MEETING 2004 (3)R.L. Powell 2004 Data Study One 20,811 Holstein bulls born in 1985 or later 17,992 Sampling status ‘S’ 2819 Sampling status ‘O’ 481,416 US SCS evaluations from 1995 through February 2004 compared to May 2004 evaluations 6,975,946 pairs of evaluations including all evaluation pairs for each bull

4. ADSA-ASAS JOINT MEETING 2004 (4)R.L. Powell 2004 Methods Study One Mean change, absolute change, SD and expected SD of change where:  Between each evaluation and the May 2004 evaluation, for all bulls and by sampling status  Within all pairs of evaluations, by change in reliability (REL) E(SD) = SD sire  REL 

5. ADSA-ASAS JOINT MEETING 2004 (5)R.L. Powell 2004 Results Study One  Overall, May 2004 PTA SCS were greater than earlier evaluations  SD of change in evaluations were larger than E(SD)  For evaluations prior to 2000, SD of change averaged 19% larger than E(SD)  For later evaluations, SD of change was 10% larger than E(SD)

6. ADSA-ASAS JOINT MEETING 2004 (6)R.L. Powell 2004 Results Study One  SD of change exceeded E(SD) more with smaller increases in REL  For changes in REL less than.05, SD of change was 25% greater than E(SD)  For changes in REL from.10 to.30, SD of change was 8% greater than E(SD)  Sampling status can affect accuracy ‘O’ bull first evaluations changed less but increased less in REL ‘S’ bull evaluations with an opportunity for 2nd crop daughters more accurate

7. ADSA-ASAS JOINT MEETING 2004 (7)R.L. Powell 2004 Data Study Two 13,624 Holstein bulls with only US daughters in Interbull evaluations for May 2001 1028 Holstein bulls with US and additional foreign daughters included in Interbull evaluations

8. ADSA-ASAS JOINT MEETING 2004 (8)R.L. Powell 2004 Methods Study Two Correlations of 2001 with 2004 evaluations and regressions of 2004 on 2001 evaluations  By increase in US daughters from 2001 to 2004  For bulls with Interbull evaluations including: US daughters only (US-only) US and foreign daughters (Multi-country)

9. ADSA-ASAS JOINT MEETING 2004 (9)R.L. Powell 2004 Results Study Two Number of bulls Correlation of IB01 with IB04 US01 with US04 IB01 with US04 US-only bulls13,6240.9600.9630.962 >25%  daus 1 17150.8490.854 >50%  daus 1 12110.8350.841 >100%  daus 1 8550.8290.8350.836 >200%  daus 1 5690.8080.8130.814 Multi-country bulls10280.9720.9700.929 >25%  daus 1 1950.9360.9090.912 >50%  daus 1 1490.9260.8890.905 >100%  daus 1 1020.9000.8500.874 1 Percent increase in US daughters from May 2001 to May 2004.

10. ADSA-ASAS JOINT MEETING 2004 (10)R.L. Powell 2004 Results Study Two Number of bulls Correlation of IB01 with IB04 US01 with US04 IB01 with US04 US-only bulls13,6240.9600.9630.962 >25%  daus 1 17150.8490.854 >50%  daus 1 12110.8350.841 >100%  daus 1 8550.8290.8350.836 >200%  daus 1 5690.8080.8130.814 Multi-country bulls10280.9720.9700.929 >25%  daus 1 1950.9360.9090.912 >50%  daus 1 1490.9260.8890.905 >100%  daus 1 1020.9000.8500.874 1 Percent increase in US daughters from May 2001 to May 2004.

11. ADSA-ASAS JOINT MEETING 2004 (11)R.L. Powell 2004 Results Study Two Number of bulls Regression of IB04 on IB01 US04 on US01 US04 on IB01SE US-only bulls13,6240.99 0.002 >25%  daus 1 17151.011.001.010.01-0.02 >50%  daus 1 12111.00 0.01 >100%  daus 1 8551.001.01 0.02 >200%  daus 1 5690.991.00 0.03 Multi-country bulls10280.98 0.890.01 >25%  daus 1 1950.990.970.960.03 >50%  daus 1 1490.980.950.940.03-0.04 >100%  daus 1 1020.970.950.930.06-0.08 1 Percent increase in US daughters from May 2001 to May 2004.

12. ADSA-ASAS JOINT MEETING 2004 (12)R.L. Powell 2004 Conclusions  Mean PTA SCS tended to increase slightly over time and as REL increased  Addition of daughters caused greater than expected changes in PTA SCS  Correlations and regressions of US and Interbull 2001 and 2004 evaluations were near expectations  Foreign data improved prediction of later US PTA