Contribution of inbreeding and recessive defects to early embryo loss 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 Service sire Cow sire NR70 deviation Embryo inbreeding (%) Services (no.) Name CVM status* Worst 5 interactions + inbreeding effects United Nick … Norrielake Cleitus Luke –0.0356 4.7 124 Maizefield Bellwood – –0.0344 25.0 33 Stardell Valiant Winken To-Mar Blackstar –0.0320 0.0 66 Schutzs Brass Bell GLC Jordache –0.0319 217 Robthom Integrity –0.0313 0.7 251 Best 5 interactions + inbreeding effects Paradise-R Cleitus Mathie + Regancrest Mascot Dello 0.0288 0.2 199 Paradise-R Roebuck MJR Blackstar Emory 0.0278 502 Shen-Val NV LM Formation 0.0273 1.6 208 Scil Buckeye 0.0270 227 Coyne Farms Bonanza Howcrest Aristides 3.1 189 Worst 5 interactions (excluding inbreeding effects) –0.0310 –0.0305 0.8 Pen-Col Duster –0.0283 Best 5 interactions (excluding inbreeding effects) 0.0300 0.0290 Shen-Val NV LM Fashion The Choice of Mark Adam 0.0283 4.0 121 *Negative (–), positive (+), and not tested (…) 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