Genetic relationships among fertility traits of Holsteins and Jerseys (abstract 351)

1. Genetic relationships among fertility traits of Holsteins and Jerseys(abstract 351) H.D. NORMAN* (dnorman@aipl.arsusda.gov, 301-504-8334), R.H. MILLER, P.M. VANRADEN, and J.R. WRIGHT Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, MD 20705-2350 J.S. CLAY North Carolina State University, Raleigh, NC 27603‑3435

2. Why evaluate fertility traits? • Low heritability estimates but large phenotypic variation • High economic value • Decline in reproductive performance • Antagonistic relationship between milk yield and reproductive traits

3. Objectives • Estimate genetic relationships among fertility traits • Determine which reproductive traits have greatest potential use for evaluating daughter fertility of bulls

4. Management factors • Voluntary waiting period between calving and first breeding • Use of bST • Designed reproductive programs

5. Data processing factors • Computer program differences among dairy records processing centers • DHI reproduction options • Calving interval estimation without subsequent calving date

6. Data • 2.2 million Holstein and 0.2 million Jersey breeding records from 1995 through 2000 that included: • Yield (milk, fat, protein) for first 3 test days • Identification (service sire, cow, sire, dam) • DIM at each service • Parity • DHI herds with records processed by: • AgriTech Analytics • AgSource Cooperative Sources • Dairy Records Management Systems • Pennsylvania DHI Association

7. Data restrictions • <150 DIM at third test day • Daily milk yield between 4.5 and 109 kg • Test-day component percentage between 2.0 and 8.0 • Fat and protein percentages reported for at least 2 of first 3 test days

8. Fertility traits • Days from calving to first service • Days from calving to last reported service (days open) • Nonreturn to first service within 70 d (nonreturn rate) • Number of services

9. Fertility restrictions • Successful breeding if cow not reported in estrus or rebred within 70 d • Breedings excluded: • Virgin heifers • <15 or >365 DIM • Cows that left herd <70 d after first service • Subsequent breedings within 4 d • Non-AI first services • Herd: • >9 AI matings annually • >9 or <90% for annual mean for nonreturn rate

10. Means

11. Analysis • Fertility traits adjusted for: • Parity (fixed; 1, 2, … 5, 5+) • Age deviation within parity (linear regression) • 2 highest test-day yields (linear regression): • Milk • Fat • Protein • Lactation stage at first service (nonreturn rate and number of services only)

12. Analysis (continued) • Heritabilities and genetic correlations estimated with multitrait REML sire model: • Observations from 1998 to 2000 • 3447 Holstein bulls with 40 daughters • 2602 Jersey bulls

13. Heritability estimates (%)

14. Genetic correlations

15. Phenotypic correlations

16. Conclusions • Days open has higher heritability than nonreturn rate • Days open has moderate to high genetic correlation with days to first service and number of services • Days open appears to be best single measure among fertility traits examined for genetic evaluation of cow fertility