Genetic Evaluation of Cow Fertility expressed as Pregnancy Rate

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Genetic Evaluation of Cow Fertility expressed as
Pregnancy Rate
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Factors Affecting Fertility

• Service bull
• Sperm motility, abnormality, etc. measured by AI
  companies
• ERCR ratings from DRMS_at_Raleigh
• Environment and genes of cow
• Interaction of bull and cow
• Lethal recessives, inbreeding

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Pregnancy Rate

• Rate that cows become pregnant
• Can be derived from days open
• Non-linear 21 / (DO VWP 11)
• Linear approx (233 DO) / 4
• Advantages over days open
• Positive numbers are desirable
• Earlier measure of herd fertility

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Distribution of Days OpenHolstein Calvings 1990
- 2001
Cows culled for reproductive reasons
50
250
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Average breed effects across regions and time by
calving month
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Regional effects for Holsteins calving since 1997
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Parameter Estimates Multi-trait REML analysis of
first lactations
Heritability of DO Heritability of DO 3.7 3.7
Correlations with DO Phenotypic Genetic
Milk Milk .11 .38
Fat Fat .09 .33
Protein Protein .10 .32
SCS SCS .05 .30
PL PL -.20 -.59
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Pregnancy Rate Evaluation

• Lactations 1-5 beginning with 1960
• Data sources
• Reported DO confirmed with next calving
• Exclude most recent 9 months
• Reported DO if no next calving
• Exclude most recent 9 months
• Calving interval 280 days if no reported DO
• Exclude most recent 18 months
• Assigned DO 250 if sold for infertility

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Evaluation Methods

• BLUP Animal Model
• Same programs used for yield, PL, SCS
• Convert to preg rate (233 DO) / 4
• Adjust for heterogeneous variance
• Parameter estimates used
• Heritability 4
• Repeatability 11
• Sire-by-herd interaction 1

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Evaluation Test Run

• Holstein data from Aug 2002 evaluation
• 40 million lactations
• 16 million cows
• Statistics for recent, well-sampled bulls
• Born 1994 - 1997
• Milk REL gt 80 (mean 87)
• 4215 Holstein bulls
• 314 Jersey bulls
• Example evaluations for older sires

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Recent Bull Evaluations
Holstein Jersey
Pregnancy Rate
PTA range -4.8 to 2.8 -3.0 to 1.5
REL mean 59 57
PTA correlations
PL .46 .23
SCS -.13 .03
Milk -.22 -.22
Fat -.18 -.35
Protein -.16 -.17
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Older Bull Evaluations
REL DO DPR PL NM
Duster 99 -7 1.8 4.3 442
Bellwood 99 1 -.3 -.5 361
Mandel 99 9 -2.3 -.6 248
Luke 99 11 -2.8 -1.8 135
Mountain 99 -3 .8 1.1 280
Mascot 99 5 -1.3 -2.9 29
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Pregnancy Rate Genetic Trend 1957-1999
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Phenotypic Trend Holstein DO
Lactation
5th
4th
3rd
2nd
1st
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Conclusions

• Daughter Pregnancy Rate has low heritability
  (4) but high genetic correlation with
  Productive Life (gt.5)
• Official evaluations for DPR planned for February
  2003
• Selection on PL has greatly reduced the decline
  in cow fertility
• Economic value not yet determined

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Acknowledgments

• All DHIA herds and processing centers contributed
  data
• George Wiggans and Lillian Bacheller improved the
  fertility database
• John Clay suggested expressing cow fertility as
  pregnancy rate