# Presentation: 164070

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

## 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.**

## Stillbirth Definition

**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 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).**

## Stillbirth Data

|  | Alive | Dead | Died | Usable |
| --- | --- | --- | --- | --- |
| Parity | 1 | 2 | 3 | Records |
| 1 | 88.6% | 10.9% | 0.5% | 1,596,693 |
| 2+ | 94.7% | 4.8% | 0.5% | 4,448,187 |
| Usable Records | 5,627,952 | 387,606 | 29,322 | 6,044,880 |

**Stillbirth Score**

## 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 1996****–****2000;**
**Maternal:**** bulls born 1991****–****1995.**

## Phenotypic Trend for Stillbirths

## Genetic Trend for Stillbirths

## Distribution of PTA

## Distribution of Reliabilities

## 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.**

## Correlations among domestic and Interbull SB solutions (≥90% Rel on both scales)

|  | Direct | Maternal |
| --- | --- | --- |
| Switzerland | 0.90 | 0.85 |
| Denmark | 0.78 | 0.75 |
| Finland | 0.65 | 0.96 |
| Netherlands | 0.71 | 0.69 |
| Sweden | 0.63 | 0.89 |

## Genetic Correlations Among SB and CE

| Trait |  | CE |  |  | SB |  |
| --- | --- | --- | --- | --- | --- | --- |
|  |  | Direct | Maternal |  | Direct | Maternal |
| CE | Direct | 1.00 | 0.46 |  | 0.67 | 0.25 |
|  | Maternal |  | 1.00 |  | 0.29 | 0.63 |
| SB | Direct |  |  |  | 1.00 | 0.28 |
|  | Maternal |  |  |  |  | 1.00 |

## 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).**

## 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.**

## 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.**

## Acknowledgments

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