Completeness of metabolic disease recordings in Nordic national databases for dairy cows

The four Nordic countries Denmark (DK), Finland (FI), Norway (NO) and Sweden (SE) all have national databases where diagnostic events in dairy cows are recorded. Comparing and looking at differences in disease occurrence between countries may give information on factors that influence disease occurrence, optimal diseases control and treatment strategies. For such comparisons to be valid, the data in these databases should be standardised and of good quality. The objective of the study presented here was to assess the quality of metabolic disease recordings, primarily milk fever and ketosis, in four Nordic national databases. Completeness of recording figures of database registrations at two different levels was chosen as a measure of data quality. Firstly, completeness of recording of all disease events on a farm regardless of veterinary involvement, called 'Farmer observed completeness', was determined. Secondly, completeness of recording of veterinary treated disease events only, called 'Veterinary treated completeness', was determined. To collect data for calculating these completeness levels a simple random sample of herds was obtained in each country. Farmers who were willing to participate, recorded for 4 months in 2008, on a purpose made registration form, any observed illness in cows, regardless of veterinary involvement. The number of participating herds was 105, 167, 179 and 129 in DK, FI, NO and SE respectively. In total these herds registered 247, 248, 177 and 218 metabolic events for analysis in DK, FI, NO and SE, respectively. Data from national databases were subsequently extracted, and the two sources of data were matched to find the proportion, or completeness, of diagnostic events registered by farmers that also existed in national databases. Matching was done using a common diagnostic code system and allowed for a discrepancy of 7 days for registered date of the event. For milk fever, the Farmer observed completeness was 77%, 67%, 79% and 79%, and for Veterinary treated completeness 88%, 71%, 80% and 82%, in DK, FI, NO and SE, respectively. For ketosis, the Farmer observed completeness was 77%, 55%, 70% and 46%, and for Veterinary treated completeness 84%, 75%, 79% and 56%, in DK, FI, NO and SE, respectively. The differences observed in some of these completeness figures indicate that metabolic disease frequency measures when calculated from these four national databases do not accurately reflect the true difference in metabolic disease occurrence in dairy cows between countries. Further standardisation of disease registrations is necessary for valid between-country assessments.