# Presentation: 237798

## Estimation of Stillbirth (Co)variance Components and Development of a Calving Ability Index

## Introduction

**A national evaluation for stillbirth (****SB****) for Holstein will be implemented in August 2006.**
**(C****o)variance components were required.**
**A calving ability index (****CA$****) which includes SB and calving ease (****CE****) was developed.**

## Stillbirth

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

| 1 = calf born alive, |
| --- |
| 2 = calf born dead, |
| 3 = calf died within 48 h of parturition. |

## Data

**7 million SB records were available for Holstein cows calving since 1980.**
**Calvings with unknown MGS were eliminated for VCE.**
**Records with sire and MGS among the 2,600 most-frequently appearing bulls were selected.**

## Data (cont’d)

**Herds needed ≥10 calving records with SB scores of 2 or 3 in the database to be included.**
**Herd-years were required to include ≥20 records and only single births were used.**
**Inclusion of all records for a cow was not guaranteed.**
**The final dataset included ****2,083,979**** calving records from ****5,765**** herds and ****33,304**** herd-years.**

## Sampling

**Six datasets of ****~250,000**** records each were created by randomly sampling herd codes without replacement.**
**Datasets ranged from ****239,192**** to ****286,794**** observations, and all averaged ****7%**** stillbirths.**
**A common pedigree file was used to facilitate comparisons between sire and MGS solutions.**

## Modeling and Estimation

**A S-MGS threshold model was used.**
**Fixed:**** year-season, parity-sex, sire and MGS birth year;**
**Random:**** herd-year, sire, MGS.**
**Estimation was by quasi-REML and Gibbs sampling.**
**CBLUP90REML**** and ****THRGIBBS1****.**

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## (Co)variance Components Estimated by Quasi-REML

| Sample | Var(Sire) | Var(MGS) | Cov(S-MGS) |
| --- | --- | --- | --- |
| 1 | 0.008 | 0.016 | 0.004 |
| 2 | 0.007 | 0.015 | 0.004 |
| 3 | 0.008 | 0.017 | 0.005 |
| 4 | 0.007 | 0.017 | 0.004 |
| 5 | 0.007 | 0.016 | 0.002 |
| 6 | 0.008 | 0.015 | 0.004 |
| Mean | 0.008 | 0.016 | 0.004 |

## (Co)variance components estimated by Gibbs sampling

|  | Var(Sire) |  |  | Var(MGS) |  |  | Cov(S-MGS) |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Sample | Mean | SD |  | Mean | SD |  | Mean | SD |
| 1 | 0.010 | 0.002 |  | 0.018 | 0.002 |  | 0.004 | 0.001 |
| 2 | 0.007 | 0.002 |  | 0.017 | 0.002 |  | 0.005 | 0.001 |
| 3 | 0.009 | 0.001 |  | 0.019 | 0.002 |  | 0.005 | 0.001 |
| 4 | 0.008 | 0.001 |  | 0.019 | 0.002 |  | 0.004 | 0.001 |
| 5 | 0.008 | 0.001 |  | 0.018 | 0.002 |  | 0.002 | 0.001 |
| 6 | 0.009 | 0.002 |  | 0.017 | 0.002 |  | 0.004 | 0.001 |
| Mean | 0.009 | 0.002 |  | 0.018 | 0.002 |  | 0.004 | 0.001 |

## Heritabilities and Correlations

|  |  | Heritability (%) |  |  |  | Correlation |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Method | Statistic | Direct | Maternal | MGS |  | rD,M |  | rD,MGS |
| GS | Min | 2.6 | 5.2 | 6.1 |  | −0 | .25 | 0.18 |
|  | Max | 3.4 | 6.5 | 6.9 |  | 0 | .17 | 0.41 |
|  | Mean | 3.0 | 5.8 | 6.5 |  | −0 | .02 | 0.33 |
| REML | Min | 2.4 | 4.6 | 5.4 |  | −0 | .28 | 0.20 |
|  | Max | 3.1 | 5.7 | 6.3 |  | 0 | .16 | 0.40 |
|  | Mean | 2.7 | 5.1 | 5.8 |  | 0 | .00 | 0.34 |

## (Co)variance Components Summary

**Heritability estimates were slightly lower than literature estimates.**
**Direct-maternal genetic correlations were much smaller than previous reports.**
**Mean Gibbs sampling estimates were used in the national evaluation.**

## Economic Assumptions

**Newborn calf value**
**Expenses per difficult birth (CE ≥4) **

| $450 for females |
| --- |
| $150 for males |

| $75 labor and veterinary |
| --- |
| $100 reduced milk yield |
| $75 reduced fertility and longevity |
| 1.5% chance of cow death ($1800) |

## Genetic Correlations Among Traits in Calving Ability Index

| Trait |  | Calving Ease |  |  | Stillbirth |  |
| --- | --- | --- | --- | --- | --- | --- |
|  |  | Sire | Dau |  | Sire | Dau |
| Calving Ease | Sire | 1.00 | 0.46 |  | 0.67 | 0.25 |
|  | Dau |  | 1.00 |  | 0.29 | 0.63 |
| Stillbirth | Sire |  |  |  | 1.00 | 0.28 |
|  | Dau |  |  |  |  | 1.00 |

## Properties of the Calving Ability Index

|  | Calving Ease |  |  |  |  | Stillbirth |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | Paternal |  | Maternal |  |  | Paternal |  | Maternal |  |
| Mean | 8 |  | 8 |  |  | 8 |  | 8 |  |
| SD | 1 | .7 | 1 | .4 |  | 1 | .0 | 1 | .7 |
| Heritability, % | 8 | .6 | 4 | .8 |  | 3 | .0 | 6 | .5 |
| Economic value, $ | 4 |  | 3 |  |  | 4 |  | 8 |  |

## National Calving Trait Indices

| Cntry | Pat CE |  | Mat CE |  | Pat SB |  | Mat SB |  | Model | Merit % |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| DEU | 19 |  | 26 |  | 26 |  | 29 |  | AM | 7 |  |
| NLD | 33 |  | 17 |  | 33 |  | 17 |  | S-MGS | 7 |  |
| NOR | 0 |  | 34 |  | 33 |  | 33 |  | S-MGS | 3 |  |
| SWE | 12 |  | 38 |  | 12 |  | 38 |  | S-MGS | 12 |  |
| CHE | 12 |  | 12 |  | 38 |  | 38 |  | AM | 0 |  |
| USA | 55 |  | 45 |  | 0 |  | 0 |  | S-MGS | 4 | (2003) |
| USA | 25 |  | 15 |  | 15 |  | 45 |  | S-MGS | 6 | (2006) |

## Calving Ability Index

**CA$ has a genetic correlation of ****0.85**** with the combined SCE and DCE values in 2003 NM$ and ****0.77**** with DCE in TPI.**
**Calving traits will receive ****6%**** of the total emphasis in the August 2006 revision of NM$.**

## Breeds Other Than Holstein

**Brown Swiss**** economic values are   ****−6**** for SCE and ****−8**** for DCE.**
**Separate SB evaluations are not available.**
**CE values include the correlated response in SB.**
**Other breeds**** will be assigned CA$ of ****0.**

## Conclusions

**SB evaluations can provide additional value beyond that of CE.**
**Mating programs should assign bulls selected for high NM$ with low and high PTA for service sire effects to heifers and to cows, respectively.**

## Acknowledgments

**Ignacy Misztal and Shogo Tsuruta, University of Georgia**
**Participants in Multi-State Project S-1008**
**John Clay, Dairy Records Management Systems**