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Genetic Evaluation of Cow Fertility expressed as Pregnancy Rate

Genetic Evaluation of Cow Fertility expressed as Pregnancy Rate. Factors Affecting Fertility. Service bull Sperm motility, abnormality, etc. measured by AI companies ERCR ratings from DRMS@Raleigh Environment and genes of cow Interaction of bull and cow Lethal recessives, inbreeding.

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Genetic Evaluation of Cow Fertility expressed as Pregnancy Rate

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  1. Genetic Evaluation of Cow Fertility expressed as Pregnancy Rate

  2. Factors Affecting Fertility • Service bull • Sperm motility, abnormality, etc. measured by AI companies • ERCR ratings from DRMS@Raleigh • Environment and genes of cow • Interaction of bull and cow • Lethal recessives, inbreeding

  3. Pregnancy Rate • Rate that cows become pregnant • Can be derived from days open • Non-linear: 21 / (DO – VWP + 11) • Linear approx: (233 – DO) / 4 • Advantages over days open • Positive numbers are desirable • Earlier measure of herd fertility

  4. Distribution of Days OpenHolstein Calvings 1990 - 2001 Cows culled for reproductive reasons ≤ 50 ≥ 250

  5. Average breed effects across regions and time by calving month

  6. Regional effects for Holsteins calving since 1997

  7. Parameter EstimatesMulti-trait REML analysis of first lactations

  8. Pregnancy Rate Evaluation • Lactations 1-5 beginning with 1960 • Data sources • Reported DO confirmed with next calving • Exclude most recent 9 months • Reported DO if no next calving • Exclude most recent 9 months • Calving interval – 280 days if no reported DO • Exclude most recent 18 months • Assigned DO = 250 if sold for infertility

  9. Evaluation Methods • BLUP Animal Model • Same programs used for yield, PL, SCS • Convert to preg rate = (233 – DO) / 4 • Adjust for heterogeneous variance • Parameter estimates used: • Heritability = 4% • Repeatability = 11% • Sire-by-herd interaction = 1%

  10. Evaluation Test Run • Holstein data from Aug 2002 evaluation • 40 million lactations • 16 million cows • Statistics for recent, well-sampled bulls • Born 1994 - 1997 • Milk REL > 80% (mean = 87%) • 4215 Holstein bulls • 314 Jersey bulls • Example evaluations for older sires

  11. Recent Bull Evaluations

  12. Older Bull Evaluations

  13. Pregnancy Rate Genetic Trend 1957-1999

  14. Phenotypic Trend – Holstein DO Lactation 5th 4th 3rd 2nd 1st

  15. Conclusions • Daughter Pregnancy Rate has low heritability (~4%) but high genetic correlation with Productive Life (>.5) • Official evaluations for DPR planned for February 2003 • Selection on PL has greatly reduced the decline in cow fertility • Economic value not yet determined

  16. Acknowledgments • All DHIA herds and processing centers contributed data • George Wiggans and Lillian Bacheller improved the fertility database • John Clay suggested expressing cow fertility as pregnancy rate

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