1. 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
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