Notes

Outline

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

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

Distribution of Days Open Holstein Calvings 1990 - 2001

Average breed effects across regions and time by calving month

Regional effects for Holsteins calving since 1997

Parameter Estimates Multi-trait REML analysis of first lactations

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

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%

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

Recent Bull Evaluations

Older Bull Evaluations

Pregnancy Rate Genetic Trend 1957-1999

Phenotypic Trend – Holstein DO

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

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