1. John B. Cole and Daniel J. Null Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, MD 20705-2350 john.cole@ars.usda.gov Genetic Evaluation of Age at First Calving

2. Council on Dairy Cattle Breeding, April 27, 2010 (2) Cole and Null Data First calving from January 1, 1997 to present Calving ages between 540 d (18 mo) and 1095 d (36 mo) The cow’s sire had to be ≥ 5 years old 8,234,537 HO first calvings 521,806 JE first calvings

3. Council on Dairy Cattle Breeding, April 27, 2010 (3) Cole and Null Model y = hys + a + e y = age at first calving in days hys = fixed effect of herd-year-season of birth a = random additive genetic effect e = random residual error

4. Council on Dairy Cattle Breeding, April 27, 2010 (4) Cole and Null Summary Statistics ― Cows currently milking Phenotypic Statistics BreedNMeanSDMinMax HO2,156,584763795401095 JE173,621721805401095 Genetic Statistics BreedNMeanSDMinMax HO2,154,802-0.112.03-1217 JE173,621-0.251.89-810

5. Council on Dairy Cattle Breeding, April 27, 2010 (5) Cole and Null Summary Statistics ― Active Bulls Genetic Statistics BreedNMeanSDMinMax HO732-1.073.02-1016 JE135-1.392.60-96

6. Council on Dairy Cattle Breeding, April 27, 2010 (6) Cole and Null Correlations TraitHOJE Milk-0.39-0.40 Fat-0.32-0.40 Protein-0.43-0.53 SCS-0.10-0.21 Daughter Pregnancy Rate-0.13-0.18 Productive Life-0.06-0.14 Cow Conception Rate-0.05-0.13 Heifer Conception Rate-0.33-0.20 Net Merit-0.33-0.39

7. Council on Dairy Cattle Breeding, April 27, 2010 (7) Cole and Null Correlations TraitHOJE Milk-0.39-0.40 Daughter Pregnancy Rate-0.13-0.18 Cow Conception Rate-0.05-0.13 Heifer Conception Rate-0.33-0.20 Size Composite-0.19-0.28 Productive Life-0.06-0.14 Net Merit-0.33-0.39 Correlations among PTA for bulls with reliabilities of AFC ≥ 0.90.

8. Council on Dairy Cattle Breeding, April 27, 2010 (8) Cole and Null Correlations (continued) TraitHO Maternal Calving Ease0.22 Sire Calving Ease0.08 Maternal Stillbirth0.15 Sire Stillbirth0.04 Correlations among PTA for bulls with reliabilities of AFC ≥ 0.90.

9. Council on Dairy Cattle Breeding, April 27, 2010 (9) Cole and Null Heritability of Fertility Traits Traith2h2 Age at first calving0.027 Heifer conception rate0.010 Cow conception rate0.016 Daughter pregnancy rate0.040

10. Council on Dairy Cattle Breeding, April 27, 2010 (10) Cole and Null Genetic Trend for Age at First Calving

11. Council on Dairy Cattle Breeding, April 27, 2010 (11) Cole and Null Active HO Bulls With Reliability ≥ 90% NameAFC PTAAFC Rel ROSSDALE RUDY ANTONIO-ET-7.40.91 JEWELED-ACRES SHARKY-ET-7.30.98 O-BEE MANFRED JUSTICE-ET-7.20.99 SANDY-VALLEY BOLTON-ET-7.00.97 ART-ACRES WIN 395-ET-6.10.93 NORZ-HILL FORM WIZARD-ET3.60.99 CEDARWAL APTITUDE3.70.92 KLUMBS DURHAM PONTIAC3.70.98 ROCKALLI BRADLEY4.20.97 EK-OSEEANA ASPEN-ET16.20.94

12. Council on Dairy Cattle Breeding, April 27, 2010 (12) Cole and Null Active Jersey Bulls With Reliability ≥ 90% NameAFC PTAAFC Rel SUNSET CANYON MATINEE-9.20.90 SUNSET CANYON RP MILITIA-6.90.93 RICHIES JACE TBONE A364-6.60.93 WF BROOK BOMBER-5.10.94 MILLSTREAM BELLRINGER-4.60.91 O.F. MANNIX REBEL-ET0.30.97 MASON LEMVIG JACINTO-ET0.50.93 BW LEGION0.80.95 BW COUNTRY-ET1.50.95 SHF CENTURION SULTAN2.80.93

13. Council on Dairy Cattle Breeding, April 27, 2010 (13) Cole and Null Conclusions Genetic differences exist among bulls Heritability higher than conception rate and lower than daughter pregnancy rate Heifers that are older at AFC have lower yield, lower longevity, and lower lifetime profit