Types and sources of data

Types and sources of data

Types of data

The collection of direct information on health and disease status of individual animals is preferable to collection of indirect information. However, population-wide collection of reliable health information may be easier to implement for indirect rather than direct measures of health. Analyses of health traits will probably benefit from combined use of direct and indirect health data, but clear distinctions must be drawn between these two types of data:

Direct health information

1. Diagnoses or observations of diseases
2. Clinical signs or findings indicative of diseases

Indirect health information

1. Objectively measurable indicator traits (e.g., somatic cell count, milk urea nitrogen, health biomarkers)
2. Subjectively assessable indicator traits (e.g., body condition score, conformation scores)

Health data may originate from different data sources which differ considerably with respect to information content and specificity. Therefore, the data source must be clearly indicated whenever information on health and disease status is collected and analysed. When data from different sources are combined, the origin of data must be taken into account when defining health traits.

In the following sections, possible sources of health data are discussed, together with information on which types of data may be provided, specific advantages and disadvantages associated with those sources, and issues which need to be addressed when using those sources.

Sources of data

Veterinarians

Content

1. Primarily report direct health data.
2. Provide disease diagnoses (documented reasons for application of pharmaceuticals), possibly supplemented by findings indicative of disease, and/or information on indicator traits.

Advantage

1. Information on a broad spectrum of health traits.
2. Specific veterinary medical diagnoses (high-quality data).
3. Legal obligations of documentation in some countries (possible utilization of already established recording practices).

Disadvantages

1. Only severe cases of disease may be reported (need for veterinary intervention and pharmaceutical therapy).
2. Possible delay in reporting (gap between onset of disease and veterinary visit).
3. Extra time and effort for recording (complete and consistent documentation cannot be taken for granted, recording routine and data flow need to be established).

Producers

Content

1. Primarily direct health data.
2. Disease observations ('diagnoses'), possibly supplemented by findings indicative of disease and/or information on indicator traits.

Advantages

1. Information on a broad spectrum of health traits.
2. Minor cases not requiring veterinary intervention may be included.
3. First-hand information on onset of disease.
4. Possible use of already-established data flow (routine performance testing, reporting of calving, documentation of inseminations).

Disadvantages

1. Risk of false diagnoses and misinterpretation of findings indicative of disease (lack of veterinary medical knowledge).
2. Possible need to confine recording to the most relevant diseases (modest risk of misinterpretation, limited extra time and effort for recording).
3. Extra documentation might be needed.
4. Need for expert support and training (veterinarian) to ensure data quality.
5. Completeness of recording may vary, and may be dependent on work peaks on the farm.

Remarks

1. Data logistics depend on technical equipment on the farm (documentation using herd management software (e.g. including tools to record hoof trimming, diseases, vaccinations,..), handheld for online recording, information transfer through personnel from milk recording agencies.
2. Possible producer-specific documentation focuses must be considered in all stages of analyses (checks for completeness of health / disease incident documentation; see Kelton et al., 1998).
3. Preliminary research suggests that epidemiological measures calculated from producer-recorded data are similar to those reported in the veterinary literature (Cole et al., 2006).

Expert groups (claw trimmer, nutritionist, etc.)

Content

Direct and indirect health data with a spectrum of traits according to area of expertise.

Advantages

1. Specific and detailed information on a range of health traits important for the producer (high-quality data),
2. Possible access to screening data (information on the whole herd at a given point in time),
3. Personal interest in documentation (possible utilization of already-established recording practices)

Disadvantages

1. Limited spectrum of traits,
2. Dependence on the level of expert knowledge (certification/licensure of recording persons may be advisable),
3. Extra time and effort for recording (complete and consistent documentation cannot be taken for granted, recording routine and data flow need to be established)
4. Business interests may interfere with objective documentation

Others (laboratories, on-farm technical equipment, etc.)

Content

Indirect health data with spectrum of traits according to sampling protocols and testing requests, e.g., microbiological testing, metabolite analyses, hormone tests, virus/bacteria DNA, infrared-based measurements (Soyeurt et al., 2009a,b).

Advantages

1. Specific information on a range of health traits important for the producer (high quality data).
2. Objective measurements.
3. Automated or semi-automated recording systems (possible utilization of already established data logistics).

Disadvantages

1. Interpretation with regard to disease relevance not always clear.
2. Validation and combined use of data may be problematic.

Table 1. Overview of the possible sources of direct and indirect health information.

Source of data	Type of data
	Direct health information	Indirect health information
Veterinarian	Yes	Possibly
Producer	Yes	Possibly
Expert groups	Yes	Possibly
Others	No	Yes