1. ADSA 2002 (RHM-P1) 2002 R.H. Miller, ,1 H.D. Norman, 1 and J.S. Clay 2 1 Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350; 2 North Carolina State University, Raleigh, NC 27603 ‑ 3435 Abstr. 1390 Factors affecting fertility traits of Holsteins and Jerseys

2. ADSA 2002 (RHM-P2) 2002 INTRODUCTION Data on fertility would allow the development of genetic evaluations and economic indexes that could be used to offset the decline in reproductive performance associated with selection for high yield. Female fertility already is evaluated in several nations; U.S. international competitiveness might improve if U.S. progeny-test programs provided fertility data. Research is needed to model genetic and environmental factors that affect fertility, to determine value of genetic gains for reproduction, and to determine how breeders should balance long term goals.

3. ADSA 2002 (RHM-P3) 2002 OBJECTIVES To assess effects on fertility of: Stage of lactation at first service. Parity and age within parity. Peak test-day yield for milk, fat, and protein.

4. ADSA 2002 (RHM-P4) 2002 DATA Records from 3.6 million Holstein and 0.26 million Jersey lactations in 17,445 and 1177 herds, respectively, in 47 States. First services (Jan. 1995 – Dec. 2000). AI service date and service sire ID. Milk, fat, and protein yields for first 3 test days of lactation.

5. ADSA 2002 (RHM-P5) 2002 DATA (cont.) Fertility traits:  Nonreturn to first service within 70 d.  Number of services.  Days to first service.  Days to last service.  Calving interval if subsequent calving. Data edits:  Test-day yields: 4.5-109 kg for milk and 0.91-3.63 kg for fat and protein.  Mean herd-year nonreturn rate: 0.10-0.90.  Calving interval designated as missing if gestation length 302 d.

6. ADSA 2002 (RHM-P6) 2002 ANALYSIS Least squares by breed with herd-year-month of first service absorbed. Model:  Lactation stage at first service (11 groups) for nonreturn rate and number of services.  Parity (1, 2, … 5, >5).  Partial regression on peak test-day yield (milk, fat, and protein mean from 2 test days with highest energy-corrected milk among first 3 test days).  Partial regression on deviation of calving age from mean calving age for that parity. Alternative model for season: only herd-years absorbed and effect of calendar month of first service included.

7. ADSA 2002 (RHM-P7) 2002 HolsteinJersey TraitXSDX Nonreturn rate0.550.480.570.47 Number of services2.11.32.01.3 Days to first service90358331 Days to last service1417512569 Calving interval (d)4106639760 RESULTS Means and standard deviations:

8. ADSA 2002 (RHM-P8) 2002 RESULTS (cont.) Least-squares estimates:  Effect of lactation stage on nonreturn rate:

9. ADSA 2002 (RHM-P9) 2002 Least-squares estimates: (cont.)  Effect of lactation stage on number of services: RESULTS (cont.)

10. ADSA 2002 (RHM-P10) 2002 RESULTS (cont.) Least-squares estimates:  Effect of calendar month at first service on nonreturn rate:

11. ADSA 2002 (RHM-P11) 2002 TraitMilkFatProtein Holstein Nonreturn rate-0.002-0.0190.029 Number of services0.0160.096-0.168 Days to first service0.880.53-27.38 Days to last service1.825.53-37.19 Calving interval (d)1.835.94-43.72 RESULTS (cont.) Partial regressions of fertility traits on peak test-day yield (kg/d):

12. ADSA 2002 (RHM-P12) 2002 RESULTS (cont.) Partial regressions of fertility traits on peak test-day yield (kg/d): (cont.) TraitMilkFatProtein Jersey Nonreturn rate-0.003-0.0480.062 Number of services0.0220.170-0.286 Days to first service0.89-1.53-16.14 Days to last service1.974.60-28.86 Calving interval (d)2.053.63-30.01

13. ADSA 2002 (RHM-P13) 2002 CONCLUSIONS Slightly higher fertility for Jerseys than for Holsteins, but first service later during first lactation. Markedly lower fertility for first service at <90 DIM for Holsteins and at <50 d for Jerseys. Highest fertility generally in parity 3. Lowest fertility during summer and early fall; highest during spring. Decline in fertility with increase in peak yield.