Validation of the Nordic disease recording systems for dairy cattle: with special reference to clinical mastitis

The overall aim of the thesis was to validate the Nordic disease recording systems for dairy cattle, with a focus on mastitis. In the first study, Nordic dairy farmers (n=580) recorded clinical disease during four months. Their registrations were compared to records in the national cattle databases. The completeness, i.e. proportion of clinical mastitis (CM) cases recorded as veterinary-attended by farmers and found in the national databases was 0.94 (DK), 0.56 (FI), 0.82 (NO) and 0.78 (SE). In FI the incidence rate (IR) in the central database (for the sampled herds) was significantly lower than the IR of veterinary-attended CM (as recorded by farmers). The second study investigated the farmer behaviour that initiates reporting, i.e. to contact a veterinarian. A questionnaire, based on the social psychology Theory of Planned Behaviour, was distributed to dairy farmers. Focus was on cases of mild CM. Analysis of the responses (n=834) showed differences between the countries in farmers’ behavioural intention, with attitude being the most important determinant. In the third study, veterinary receipts from 112 Swedish dairy farms were compared against disease data from the Swedish Board of Agriculture (SBA) and the cattle database at the Swedish Dairy Association (SDA). The overall completeness for diagnostic events was 0.84 (SBA) and 0.75 (SDA), but varied between disease complexes, regions and veterinary employment type. The spatial distribution of veterinary-registered CM in Sweden was described in the fourth study, and areas with significantly higher or lower probability of registered CM were identified. When compared against the distribution of herds with poor udder health (indicated by high somatic cell counts) areas with suggested under-reporting of CM could be identified. In conclusion, the disease recording systems in DK, FI, NO and SE do not capture all events of CM. This is both due to differences in farmer threshold for contacting a veterinarian for a case of CM and to loss during the recording process.