Genetic Evaluation of Stillbirth in US Holsteins Using a Sirematernal Grandsire Threshold Model

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Genetic Evaluation of Stillbirth in US Holsteins
Using a Sire-maternal Grandsire Threshold Model
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Introduction

• Stillbirth is a genetically-controlled trait.
• Producers are concerned about stillbirth.
• Calf livability scores are already delivered with
  calving ease data.
• Participation in Interbull evaluations for both
  calving ease (CE) and stillbirth (SB) is
  desirable.

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Stillbirth Definition

• Reported on a three-point scale
• Scores of 2 and 3 are combined.

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Data and Edits

• 6 million SB records were available for Holstein
  cows calving since 1980.
• Herds needed 10 calving records with SB scores
  of 2 or 3 for inclusion.
• Herd-years were required to include 20 records.
• Only single births were used (no twins).

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Stillbirth Data
Stillbirth Score
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Genetic Evaluation Model

• A sire-maternal grandsire (MGS) threshold model
  was used
• Fixed year-season, parity-sex, sire and MGS
  birth year
• Random herd-year, sire, MGS.
• (Co)variance components were estimated by Gibbs
  sampling.
• Heritabilities are 3.0 (direct) and 6.5 (MGS).

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Trait Definition

• PTA are expressed as the expected percentage of
  stillbirths.
• Direct SB measures the effect of the calf itself.
• Maternal SB measures the effect of a particular
  cow (daughter).
• A base of 8 was used for both traits
• Direct bulls born 19962000
• Maternal bulls born 19911995.

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Phenotypic Trend for Stillbirths
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Genetic Trend for Stillbirths
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Distribution of PTA
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Distribution of Reliabilities
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Dystocia and Stillbirth

• Meyer et al. (2001b) make a strong argument for
  the inclusion of dystocia in models for SB.
• Difficulty of interpretation - formidable
  educational challenge.
• Interbull trait harmonization - none of the March
  2006 test run participants included dystocia in
  their models.
• Changes in sire and MGS solutions on the
  underlying scale between models were small.

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Correlations among domestic and Interbull SB
solutions (90 Rel on both scales)
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Genetic Correlations Among SB and CE
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Calving Ability Index

• CA has a genetic correlation of 0.85 with the
  combined direct and maternal CE values in 2003
  NM and 0.77 with maternal CE in TPI.
• Calving traits receive 6 of the total emphasis
  in NM (August 2006 revision).

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Conclusions

• Number of SB records (6 million) was about half
  of calving ease records (14 million).
• Reliabilities for SB averaged 45 versus 60 for
  CE.
• Phenotypic and genetic trends from 1980 to 2005
  were both small.
• An industry-wide effort is underway to improve
  recording of calf livability.

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Conclusions

• A routine evaluation for stillbirth in US
  Holsteins was implemented in August 2006.
• Direct and maternal stillbirth were included in
  NM for Holsteins starting in August 2006.
• August 2006 data were sent to Interbull for the
  September 2006 test run for calving traits.
• The US will participate in routine Interbull
  evaluations beginning in November 2006.

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Acknowledgments

• Jeff Berger, Iowa State University
• John Clay, Dairy Records Management Systems
• Ignacy Misztal and Shogo Tsuruta, University of
  Georgia