genetic improvement of dairy cattle health
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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.

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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.


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
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
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)


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.

genetic correlations between composite health and yield traits
Genetic Correlations Between Composite Health and Yield Traits

(Lyons, Freeman, and Kuck, 1991)

genetic tools currently available
Genetic Tools Currently Available

Calving Ease: Easier calving, less dystocia, fewer stillbirths (h2=0.022).

Daughter Pregnancy Rate: Improved female fertility (h2=0.040).

Productive Life: Longer working life (h2=0.085).

Somatic Cell Score: Improved resistance to mastitis (h2=0.100).

format 6
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

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 Segment

Health event code

Health event date

Health event detail (optional)

standard health event codes
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
Health Event Codes

Cystic ovary


Digestive problem/off feed

Displaced abomasum

Downer cow


Johne’s disease (clinical)



Mastitis (clinical)


Milk fever/hypocalcemia

Nervous system problem

Other reproductive problem

Respiratory problem

Retained placenta


Teat injury

Udder edema

management events
Management Events

Three management traits are also in Format 6

Body condition score

Milking speed


The format can accommodate new traits

e.g. Locomotion score

optional health event detail
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
Research Needs

Data quality edits

Individual versus composite traits

Environmental factors affecting records

Relationships among traits

Variance components estimation

Genetic evaluation models


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.