# Presentation: 065655

## Genetic Improvement of Dairy Cattle Health

## Overview

**Response to selection using field-recorded traits is efficient and well-documented.**
**Herd owners are interested in healthy, longer-lived cows.**
**Genetic variability exists for health traits of economic interest.**

## Overview

**Statistical and computational tools for genetic evaluation exist.**
**Data processing routines can be developed.**
**However, data needed for routine evaluations are limited.**

## Why select for improved health?

**Longer-lived (more profitable) cows.**
**Decreased cost of production.**
**Reduced herd turnover.**
**Improved animal welfare.**
**Genetic gains are cumulative!**

## Desirable Properties of Health Traits

**Reasonably large genetic variability or heritability.**
**Significant economic value.**
**Reasonable cost of measurement and recording.**
**Consistent methods for measurement and recording.**
- (Shook, 1989)

## Challenges

**Low heritabilities for some traits.**
**Unfavorable correlations with milk, fat, and protein yield.**
**Affected animals have a low frequency of occurrence.**
**Diagnoses may be uncertain.**
**Data are not collected in a national database.**

## Heritabilities and Correlations of Composite Health Traits

**(Lyons, Freeman, and Kuck, 1991)**

|  | Reproduct. | Mammary | Digestive | Locomotive | Respiratory |
| --- | --- | --- | --- | --- | --- |
| Reproduct. | 0.02±0.04 | -0.11* | 0.38 | 0.02 | -0.23* |
| Mammary |  | 0.12±0.06 | 0.52 | 0.84 | 0.34 |
| Digestive |  |  | 0.21±0.08 | 0.87 | 0.76 |
| Locomotive |  |  |  | 0.16±0.07 | 0.74 |
| Respiratory |  |  |  |  | 0.02±0.04 |
| * Negative genetic correlations reflect undesirable relationship. |  |  |  |  |  |

## Genetic Correlations Between Composite Health and Yield Traits

**(Lyons, Freeman, and Kuck, 1991)**

|  | Milk Yield | Fat Yield |
| --- | --- | --- |
| Reproductive | -0.27* | -0.25* |
| Mammary | 0.18 | -0.06* |
| Digestive | 0.44 | -0.06* |
| Locomotive | 0.48 | 0.45 |
| * Negative genetic correlations reflect undesirable relationship. |  |  |

## Genetic Tools Currently Available

**Calving Ease: **** Easier calving, less dystocia, fewer stillbirths (h****2****=0.022).**
**Daughter Pregnancy Rate:**** Improved female fertility (h****2****=0.040).**
**Productive Life:**** Longer working life (h****2****=0.085).**
**Somatic Cell Score:**** Improved resistance to mastitis (h****2****=0.100).**

## Holstein Daughter Pregnancy Rate (%)

## Holstein Productive Life (mos)

## Format 6

**The USDA Animal Improvement Programs Laboratory has drafted a data exchange format to collect health data.**
**It includes standard health codes.**
**The objective is to collect data for research.**
**The goal is to facilitate selection for healthier cows.**

## Format 6 Records

**Format 6 records include**
**Animal and herd identification**
**Up to 20 health event segments**
**Cow records begin with a calving and end with disposal or the next calving.**
**Heifer records begin at birth and end at first calving.**

## Health Event Segment

**Health event code**
**Health event date**
**Health event detail (optional)**

## Standard Health Event Codes

**Currently, no health event codes are used uniformly in dairy records systems.**
**Standard codes have been developed based on frequency of occurrence in field data and consultation with veterinarians.**

## Health Event Codes

**Cystic ovary**
**Diarrhea/scours**
**Digestive problem/off feed**
**Displaced abomasum**
**Downer cow**
**Dystocia**
**Johne’s disease (clinical)**
**Ketosis/acetonemia**
**Lameness**
**Mastitis (clinical)**

**Metritis**
**Milk fever/hypocalcemia**
**Nervous system problem**
**Other reproductive problem**
**Respiratory problem**
**Retained placenta**
**Stillbirth**
**Teat injury**
**Udder edema**

## Most Frequent Health Events in DRMS Data

|  | Frequency | Percent of Events* |
| --- | --- | --- |
| Mastitis | 496,531 | 19.27 |
| Lameness | 128,869 | 5.00 |
| Metritis | 126,269 | 4.90 |
| Cystic ovary | 81,936 | 3.18 |
| Retained placenta | 57,691 | 2.24 |
| Digestive problem | 47,156 | 1.83 |
| Respiratory problem | 39,918 | 1.55 |
| Ketosis | 25,541 | 0.99 |
| Displaced abomasum | 21,908 | 0.85 |
| *Frequency and percent based on 2,577,004 health event observations. |  |  |

## Management Events

**Three management traits are also in Format 6**
**Body condition score**
**Milking speed**
**Temperament**
**The format can accommodate new traits**
**e.g. Locomotion score**

## Optional Health Event Detail

- Details of problems of high economic impact (e.g. clinical mastitis)
- There is one mastitis event code.
- Organism and quarter may be reported.
- Other codes may also use this field
- Dystocia: scores of 1  to 5.
- BCS: scores of 1.00 to 5.00.

## Research Needs

**Data quality edits**
**Individual versus composite traits**
**Environmental factors affecting records**
**Relationships among traits**
**Variance components estimation **
**Genetic evaluation models**

## Summary

**Format 6 provides the framework for a national health database.**
**Selection for improved health is possible and desirable.**
**Selection complements advances in management and veterinary care.**