# Presentation: 922822

## Improvements in Dystocia National Genetic Evaluation System and Data Processing

## History

**1977 – NAAB-sponsored evaluations within AI organizations**
**1980 – NAAB-sponsored evaluations across AI organizations**
**1988 – Ordered categorical threshold model**
**1990 – Semiannual evaluations**
**1999 – Processing change from Iowa State University to USDA (November)**
**2002 – Sire-maternal grandsire (MGS) model**

## Improving Calving Ease Evaluation

**Data quality**
**Increase MGS identification**
**Improve detection of duplicate records**
**Genetic evaluation system**
**Add MGS effect to threshold model**
**Estimate parameters**

## Calving Ease Scores

**1**** = No problem during calving or calving not observed**
**2**** = Slight problem during calving**
**3**** = Moderate difficulty during calving**
**4**** = Considerable force used during calving**
**5**** = Extreme difficulty during calving**

## Frequency of Calving Difficulty

|  |  | Lactation |  |  |
| --- | --- | --- | --- | --- |
| Calving Ease Score |  | 1st | 2nd | 3rd |
| 1 |  | 63% | 80% | 81% |
| 2 |  | 14% | 10% | 9% |
| 3 |  | 14% | 7% | 7% |
| 4 |  | 5% | 2% | 2% |
| 5 |  | 3% | 1% | 1% |

## Data

**10 million calving reports since 1980**
**Pedigree data **
**From production evaluation system **
**	****Increased MGS ID from 57% to 73%**** **
**Additional 2.5 million pedigree records for cows without unique national identification**
**	****Allowing inclusion of data that does not meet requirements for production**

## Data Extraction Requirements

**Calving Data**
**Single birth**
**Dam and sire of Holstein or Red & White breed**
**Sire age >18 mo and <15 yr **
**Birth date of Jan. 1, 1980, or later**

## Sire – MGS Model

**MGS effect included**
**Evaluations of bulls as service sires improved by partially accounting for mates**
**Maternal effect on calving difficulty provided**

## Threshold model

**Scores assumed to be observations on a continuous underlying scale**
**Thresholds estimated to relate observed scores to underlying scale**

**Procedure allows for differences in amount of change between consecutive scores**

**Observed scores**

## Calving Ease Evaluation Statistics(Sire-MGS Model)

|  |  |  | Range |  |
| --- | --- | --- | --- | --- |
| Effect |  | Levels | Minimum | Maximum |
| Herd-year | 204,647 |  | -2.63 | 4.33 |
| Year-season | 44 |  | -0.88 | -0.57 |
| Parity-gender | 6 |  | -1.04 | 0.01 |
| Sire birth year | 15 |  | -0.70 | -0.62 |
| MGS birth year | 29 |  | -0.71 | -0.64 |
| Sire | 120,108 |  | -0.59 | 0.72 |
| MGS | 120,108 |  | -0.39 | 0.41 |

## Presentation of Evaluations

**Evaluations converted to expected percentage of births that would be scored 4 or 5 (difficult) for heifers (****%DBH****)**

## %DBH Distributions

## Changes in %DBH

## Sire and MGS %DBH Distributions

## Reliability

**Calculated as inverse of diagonal**
**Overestimated due to assumption of perfect accuracy of parents**

## Variance Component Estimation

**Required sire and MGS be among 2600 most common**
**Required 20 records/herd-year**
**Created 5 distinct random **
**	****sub-samples of ~200,000 records based on herd code**

## Variance Component Estimation

| Min | 6.7 | 3.9 | -.25 |
| --- | --- | --- | --- |
| Max | 8.0 | 4.4 | -.07 |
| Mean | 7.4 | 4.1 | -.15 |
| Selected | 7.9 | 4.4 | -.12 |

## Status of Evaluation System

**Test evaluations distributed to AI organizations**
**Web queries to display calving ease data available**
**First release of sire-MGS evaluations for calving ease in  ****August 2002**