Calf health monitoring in Norwegian dairy herds.

The aims of this study were to estimate the incidence of calf diseases in Norwegian dairy herds, improve calf health recordings in the Norwegian Cattle Health Recording System (NCHRS), and investigate different methods for validation of calf health data. A longitudinal, cross-sectional survey of calf health in Norway was performed between September 1, 2004, and January 31, 2007. The participating dairy herds were randomly selected from among herds registered in the Norwegian Dairy Herd Recording System as having at least 15 cow-years. Each herd participated for 1 yr. Diseases and treatments of calves of up to 180 d of age in 135 dairy herds were reported using the NCHRS. In total, 6,668 calves were born in the participating dairy herds during the project period. A total of 573 (29.6%) of the 1,936 calf health recordings reported were recordings of diseases and 1,363 (70.4%) were events of preventive therapy, dehorning, or castration. The recorded incidence of diarrhea and respiratory disease was 3.8% and 2.9%, respectively. The median age of occurrence of diarrhea and respiratory disease was 17 and 37 d, respectively. Three different methods, based on sampling of diseased calves, dehorning as an indicator of a well-functioning recording system, or feedback on degree of commitment to calf health recording, were tested to assess validation of the calf health records. The 3 methods indicated an underestimation of calf health records in the NCHRS of approximately 40% and an estimated "true" incidence of diarrhea and respiratory disease of 5.5 and 4.1%, respectively. The results from this study demonstrate the importance of encouraging farmers to conduct calf health recordings. They also indicate that finding a standardized method for validation of health data is a considerable challenge.