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Selection Differentials from National Holstein Bull Progeny Test Programs Estimated from International Data

Selection Differentials from National Holstein Bull Progeny Test Programs Estimated from International Data. Characteristics of Ideal Progeny Test Program. High pedigree merit Large number of bulls Rapid and accurate evaluation Large number of daughters/herds Intensive culling. Objective.

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Selection Differentials from National Holstein Bull Progeny Test Programs Estimated from International Data

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  1. Selection Differentials from National Holstein Bull Progeny Test Programs Estimated from International Data

  2. Characteristics of Ideal Progeny Test Program • High pedigree merit • Large number of bulls • Rapid and accurate evaluation • Large number of daughters/herds • Intensive culling

  3. Objective • Document characteristics of national progeny test (PT) programs • Age of bulls at decision • Percent of bulls retained • Standardized selection differentials (selection intensities) • Compare PT strategies of different countries

  4. Comparison Considerations • Many factors affect PT program quality • Complex relations between factors A country may have higher pedigree requirement, but return more bulls to service and have a lower selection differential.

  5. Data • Holstein Interbull evaluations • PT decisions February 1996 - 1998 • Eleven countries with at least 125 PT bulls over this period

  6. Assumptions • PT decision made on second evaluation provided by Interbull • Country of PT was country with most daughters in decision evaluation • Returned to service if 200 daughters added in country of PT from evaluations 2.5 to 4.5 years after PT decision

  7. Numbers of Bulls

  8. Numbers of Bulls

  9. Numbers of Bulls

  10. Herds, Daughters, and Reliabilities

  11. Herds, Daughters, and Reliabilities

  12. Herds, Daughters, and Reliabilities

  13. Selection Intensities

  14. Selection Intensities

  15. Selection Intensities

  16. Conclusions • Reliability at PT decision time: 80-92% • Mean bull age by country: 66-77 months • PT bulls return to service by country: 3.4-15.6% (Mean 6.9) • Selection intensities: .33-1.64 (Tended ~1) • Highest selection intensities were for protein in all 11 countries

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