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.
Longer-lived (more profitable) cows.
Decreased cost of production.
Reduced herd turnover.
Improved animal welfare.
Genetic gains are cumulative!
Reasonably large genetic variability or heritability.
Significant economic value.
Reasonable cost of measurement and recording.
Consistent methods for measurement and recording.
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.
(Lyons, Freeman, and Kuck, 1991)
(Lyons, Freeman, and Kuck, 1991)
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).
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 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 code
Health event date
Health event detail (optional)
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.
Digestive problem/off feed
Johne’s disease (clinical)
Nervous system problem
Other reproductive problem
Three management traits are also in Format 6
Body condition score
The format can accommodate new traits
e.g. Locomotion score
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.
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.