Identification of certain management practices and health data associated with Chlamydia infection status in German dairy herds.

Chlamydial infections in cattle are mostly subclinical and have been linked to disease by association rather than by experimental proof. The aim of this study was to identify indicators for estimating the probability of chlamydial infection in German dairy cattle. Variables identified as significant risk factors were narrowed down and used alongside health and/or performance data from a previous study to create models using logistic regression. The database used included 100 randomly selected herds (1074 cows). Perinatal deaths, separate calving pens, and type of insemination were strongly associated with infection status. Using the regression equation, 53/61 Chlamydia positive herds and 33/39 negative herds were correctly classified. The main indicators identified by this study can be used as a supporting tool for identifying dairy herds at risk of chlamydial infections and for developing control programmes.