[Overview on the relationship between changes in activity and ketosis in dairy cows]

With a prevalence of up to 43 % subclinical ketosis is one of the most common diseases in dairy cows in their transition period. In itself, this may cause subsequent diseases such as clinical ketosis or lameness. Therefore, monitoring of animals in this stage is of importance. In addition to the measurement of β-hydroxybutyrate or acetoacetate in blood, milk, and urine as well as the observation of the animals, computer-assisted systems are suitable means of monitoring. Information such as animal identification and activity data are recorded on a data logger and transmitted to a computer. A change in activity may be an indication of an underlying disease days before the onset of additional clinical signs. In cases of ketosis, a decrease in activity may be observed 5 days before the clinical diagnosis is made. Thus, these data are a valuable contribution in monitoring the cattle herd's health status for both the farmer and the veterinarian. Activity measurement may also be employed for the detection of a beginning lameness. In the presence of lameness, the individual's activity decreases and periods of lying are longer. Activity measurement via transponder as a part of the herd monitoring provides important information on lameness prevalence in the herd. In the presence of a lameness a visual assessment should additionally be made. Lameness scores (Locomotion score, Gait score) have been developed for this purpose and add to determining the lameness status of the herd. This way the animals are divided into different lameness classes. Based on this classification those individuals in need of claw trimming or further treatment may be identified leading to amelioration or prevention of secondary diseases. Due to lameness and subsequent reduction of activity and feed intake, the animals may develop subclinical or clinical ketosis. Therefore, under consideration of both animal welfare and economic factors early disease detection and prophylaxis is desirable and should be a main objective of herd monitoring.