Model Combining Incidence and Prevalence Data with Farm Policy to Better Explain the Observed Prevalence of Lameness in Commercial Dairies

What is the relationship between the prevalence of lame cows in herds as reported from many sources and the incidence of clinically defined problems? Prevalence data from herd surveys using locomotion scoring are usually snapshots at a single time point. Some data are available for repeated herd measures with mostly seasonal variation as the main effect on prevalence. Incidence data mostly come from herd treatment records created by hoof trimmers, veterinarians, and farmers. A three compartment state model with indirect interactions has been developed that links the population at risk, the currently affected cows, the detection interval and efficiency, the treatment interval, and the convalescing cows. Using local herd data reveals the strengths and weaknesses of current management approaches to detection and subsequent intervention strategies. Differential equations with time dependency are used that allow user inputs of known farm policies or historical farm data to create a visual output that can model ...