1. 2007 ADSA 2007 (1)H.D. Norman Effect of service sire and cow sire on gestation length H.D. Norman,* J.R. Wright, P.M. VanRaden, and J.B. Cole Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, MD 20705-2350 dnorman@aipl.arsusda.gov Abstr. 230

2. 2006 ADSA 2007 (2)H.D. Norman 2007 Objectives l Determine effect of bulls on gestation length w Service (calf) sire w Cow sire l Improve accuracy of predicting calving date

3. 2006 ADSA 2007 (3)H.D. Norman 2007 Data sources l Lactation records from dairy records processing centers (DRPCs) l Calving reports from the National Association of Animal Breeders l Pedigree records from breed associations and DRPCs l Breeding records from 2 DRPCs and Minnesota DHIA

4. 2006 ADSA 2007 (4)H.D. Norman 2007 Data edits l Inseminations after February 1998 that resulted in parturitions through December 2005 (>5 million calvings) l Animals excluded if <87% breed purity based on AIPL crossbred database l Secondary editing eliminated animals not bred to an identified AI bull

5. 2006 ADSA 2007 (5)H.D. Norman 2007 Data Characteristic Population Heifer Cow Records (no.) 311,5515,245,251 Herd-years (no.) 17,551141,008 Bulls (no.) ≥100 conceptions All (no.) 183 1,830 Active AI (no.)53103 ≥500 conceptions All (no.)61525 Active AI (no.)2230

6. 2006 ADSA 2007 (6)H.D. Norman 2007 Fixed effects in model l Conception year l Conception herd-year (absorbed) l Conception month l Age within parity l Parturition status (multiple birth, calf gender) l Lactation length l Milk yield Discrete groups (no.) 4(heifers) 8(cows) 12 5(heifers) 17(cows) 8 7 5

7. 2006 ADSA 2007 (7)H.D. Norman 2007 Random effects in model l Service sire (direct) l Cow sire (maternal) l Cow l Residual

8. 2006 ADSA 2007 (8)H.D. Norman 2007 Analysis l Bulls with ≥100 heifer and ≥100 cow conceptions w All bulls (286 service sires, 348 cow sires) −Heifers −Cows w Active-AI bulls (116 service sires, 54 cow sires) −Heifers −Cows l Repeated for bulls with ≥500 heifer and ≥500 cow conceptions (132 service sires, 105 cow sires)

9. 2006 ADSA 2007 (9)H.D. Norman 2007 Gestation length means (d) Popu- lationAyrshire Brown SwissGuernseyHolsteinJersey Animals with data passing basic edits Heifers282287285278 278½ Cows282 287½286 279½280 Animals with added requirement of an identified AI service sire Heifers—288—278 278½ Cows—288— 279½280

10. 2006 ADSA 2007 (10)H.D. Norman 2007 Gestation length SD (d) Popu- lationAyrshire Brown SwissGuernseyHolsteinJersey Animals with data passing basic edits Heifers5.26.55.85.55.4 Cows5.56.25.65.75.2 Animals with added requirement of an identified AI service sire Heifers—5.8—5.25.0 Cows—5.8—5.34.9

11. 2006 ADSA 2007 (11)H.D. Norman 2007 Fixed effects results l Conception year l Conception month l Age within parity l Parturition status l Lactation length l Milk yield – Near 0 – Summer calves arrive early – Younger animals calve sooner – Animals with twins calve early – Small negative effect – Small positive effect

12. 2006 ADSA 2007 (12)H.D. Norman 2007 Heritability estimates l Service sire l Cow sire — 34% — 12%

13. 2006 ADSA 2007 (13)H.D. Norman 2007 Gestation length PTA distribution

14. 2006 ADSA 2007 (14)H.D. Norman 2007 Active AI Holstein PTA range Effect PTA population Gestation length PTA (d) Shortest Longest Service sireHeifer −4.2 O Man 4.2 Mandelin Cow −5.3 Aspiration 5.3 Sovereign Cow sireHeifer −1.5 Darren 2.6 Silky Gibson Cow −2.1 O Man 2.3 Shandy

15. 2006 ADSA 2007 (15)H.D. Norman 2007 SD (d) of gestation length PTA Effect PTA population Bulls with ≥100 conceptions All Active AI Service sireHeifer1.431.42 Cow1.321.38 Cow sireHeifer0.750.74 Cow0.760.65

16. 2006 ADSA 2007 (16)H.D. Norman 2007 Heifer-cow PTA correlations Bull conceptionsPTA Bull status All Active AI ≥100Service sire0.96 Cow sire0.830.77 ≥500Service sire0.98 Cow sire0.910.75

17. 2006 ADSA 2007 (17)H.D. Norman 2007 Service sire-cow sire PTA correlations Bull conceptions PTA population Bull status All Active AI ≥100Heifer0.610.37 Cow0.71 ≥500Heifer0.490.24 Cow0.760.72

18. 2006 ADSA 2007 (18)H.D. Norman 2007 Conclusions l Bull differences exist and provide an opportunity to change gestation length l Genetic evaluations based on heifers or cows highly correlated for both service sire and cow sire l Genetic evaluations between service sire and cow sire moderately correlated for both heifers and cows

19. 2006 ADSA 2007 (19)H.D. Norman 2007 Conclusions (continued) l Genetic and environmental factors that impact gestation length helpful in predicting expected calving date l More research needed to determine potential value of intentional selection for either shorter or longer gestation length in addition to selection for calving ease and stillbirth