RESULTS (cont.) Deviation in NR70 for interactions of service sire with cow sire (>25 first services/combination) Pa

1. Abstr. M11 Contribution of inbreeding and recessive defects to early embryo loss P.M. VanRaden and R.H. Miller* Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350 INTRODUCTION • Reproductive traits adversely affected by inbreeding because of large nonadditive genetic variance • Recent interest in crossbreeding because of declining female reproductive efficiency • Recessive genetic defects that cause embryonic death expressed as complete dominance and add to fraction of nonadditive genetic variance • Complex vertebral malformation (CVM) Swedish Holstein carrier bulls had lower 168-d nonreturn rates; no difference for 28- and 56-d nonreturn rates (Persson, 2003, Undergraduate Thesis, Swedish Agric. Univ., Uppsala) • Deficiency of uridine monophosphate synthase (DUMPS) • Probability that mates will be carriers for same genetic defect increased by inbreeding METHODS • Model included herd-year-season, cow parity, cow sire, service sire, regression on inbreeding, and interaction of service sire and cow sire • Service sire effects constant and uncorrelated across time • Additive relationship matrix for cow sire • Dominance relationship matrix for interaction • Additive ×additive effects not included • Variance estimation (Hoeschele, 1991, J. Dairy Sci. 74:1743) • REML for main effects and data adjusted • Tilde-hat REML approximation for interaction effect • Analysis to determine if bull CVM and DUMPS status explained variation in interaction effect RESULTS (cont.) • Deviation in NR70 for interactions of service sire with cow sire (>25 first services/combination) • Paradise-R Cleitus Mathie • Maximum number of matings to own daughters (154) • Maximum frequency for individual CVM carrier carrier combinations (792 with Highlight Mr Mark Cinder) • Included in 5 of the 10 most frequent CVM carrier  carrier combinations RESULTS • Regression of NR70 on inbreeding of embryo was –0.096 per 1% increase in inbreeding, which could be explained by fatal defects in >20% of embryos • 348 bulls mated to own daughters • Variation • Service sire: 0.36% • Cow sire: 0.24% (heritability of 1.0%) • Interaction: 0.18% (dominance variance of 2.8%) • Interaction of service sire with cow sire • Total of 369,017 bull combinations • Mean of 6 records per bull combination • 50 bull pairs with>500 records (maximum of 2077) and reliability of >50% • Estimates (compared to mean NR70 of 56%) • Including inbreeding effect: –3.6 to 2.9% • Excluding inbreeding effect: –3.2 to 3.5% • CVM/DUMPS status • 2195 combinations included 2 known CVM carriers • No indication that CVM or DUMPS status explained variation in NR70 OBJECTIVES • Using 70-d nonreturn rate (NR70) as a measure of reproduction, determine • Magnitude of nonadditive genetic variance • Effects of inbreeding • Extent that recessive genetic defects contribute to nonadditive variance DATA • NR70 based on 1.74 million first AI services of US Holsteins from 1995 through 2000 • All dairy records processing centers represented except DHI-Provo • 1,251 bulls included as cow sire or service sire • >100 daughters for cow sires • >500 first services for service sires • Genotyping results to determine bull CVM and DUMPS carrier status DATA • NR70 based on 1.74 million first AI services of US Holsteins from 1995 through 2000 • All dairy records processing centers represented except DHI-Provo • 1,251 bulls included as cow sire or service sire • >100 daughters for cow sires • >500 first services for service sires • Genotyping results to determine bull CVM and DUMPS carrier status CONCLUSIONS • Substantial negative impact from increased embryo inbreeding on conception and 70-d survival after insemination • Substantial dominance variance for NR70 (nearly 3 times larger than additive variance) • Variation in NR70 not related to status of service sire or cow sire for CVM (losses later in gestation) or DUMPS (few carrier bulls) • Investigation of embryo loss later in gestation needed to determine impact of bull CVM status