Comparison of Holstein service-sire fertility for heifer and cow breedings with conventional and sexed semen H. D. Norman*, J. L. Hutchison, and P. M. VanRaden Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD Abstr. W RESULTS (continued)  High correlations between cow and heifer SCR within semen type  0.68 (August 2009) and 0.67 (January 2010) for conventional semen  0.73 (August 2009) and 0.75 (January 2010) for sexed semen  Low correlations between conventional- and sexed-semen SCR within first and later parities  0.10 (August 2009) and 0.18 (January 2010) for cows  – 0.22 (August 2009) and 0.08 (January 2010) for heifers  Correlations between August 2009 and January 2010 SCR  High correlations between corresponding models (0.96 to 0.98)  High correlations between cow and heifer SCR with same semen type (0.62 to 0.78)  Low correlations between conventional- and sexed-semen SCR RESULTS  Summary statistics  Mean SCR near 0.0% for all data sets  Mean reliabilities near 80% for conventional-semen SCR; slightly lower for sexed-semen SCR  High SD for heifer sexed-semen SCR (5.78 for August 2009 and 4.34 in January 2010)  Correlations between SCR (above diagonal) and genetic correlations [r G AB = r AB /√(REL A /100)(REL B /100); Calo et al., 1973, JAS 37:676] for true SCR (below diagonal) DATA & METHODS  Holstein breeding reports provided by dairy records processing centers  Data edits  Most recent 4 yr of inseminations  Services between 30 and 365 DIM  >4,536 kg milk  Herd-year with >50% milking cows with recorded breedings  Herd conception rate between 10 and 90%  No ET donors  SCR model based on confirmed conception rate with variables for herd- year-season-parity-registration status, parity, service number, year-state- month, cow age, milk yield, short cycle between matings, bull age, inbreeding of service sire and embryo, stud-mating year  Parity removed from models with heifer data  Service-sire age groups consolidated for sexed-semen breedings  AI Holstein bulls with ≥300 breedings in ≥10 herds overall and ≥100 matings during the last 12 mo summarized CONCLUSIONS  Models appear to be consistent across consecutive evaluations  Fertility rankings for sexed semen differ considerably from conventional evaluations and warrant separate SCR  Combining cow and heifer breedings could be advantageous INTRODUCTION Sire conception rate (SCR), a phenotypic fertility evaluation for service sires, was implemented by USDA in August The evaluation is based on the first 7 conventional-semen breedings for parities 1 through 5 and contains 14 effects to predict bull conception rate. OBJECTIVE To compare official SCR evaluations (C cow ) with SCR from 3 alternative data sets:  Conventional-semen breedings for primiparous heifers (C heifer )  Sexed-semen breedings from parities 1 through 5 (S cow )  Sexed-semen breedings for primiparous heifers (S heifer ) Data set August 2009January 2010 C cow 13,213,12613,216,858 C heifer 1,583,2011,515,395 S cow 56,99458,876 S heifer 189,526222,988 Mean matings/ bull, n ModelBulls, n SCR, % Reliability, % MeanSD August 2009 C cow 2,328– ,393 C heifer ,592 S cow ,153 S heifer ,306 January 2010 C cow 2, ,297 C heifer ,321 S cow 25– ,263 S heifer ,313 ModelC cow C heifer S cow S heifer August 2009 C cow … –0.08 C heifer 1.00…–0.05 –0.22 S cow –0.15–0.07… 0.73 S heifer – … January 2010 C cow … C heifer 0.82… S cow … 0.75 S heifer … January 2010 August 2009 C cow C heifer S cow S heifer C cow –0.05 C heifer –0.14 S cow S heifer