Modelling the Economic Impact of Three Lameness Causing Diseases Using Herd and Cow Level Evidence Modelling the Economic Impact of Three Lameness Causing Diseases Using Herd 1 and Cow Level Evidence 2 3

A.R. 2010. Modelling the economic impact of three lameness causing diseases using herd and cow level evidence. Abstract 16 Diseases to the cow's hoof, interdigital skin and legs are highly prevalent and of large 17 economic impact in modern dairy farming. In order to support farmer's decisions on 18 preventing and treating lameness and its underlying causes, decision support models 19 can be used to predict the economic profitability of such actions. An existing 20 approach of modelling lameness as one health disorder in a dynamic, stochastic and 21 mechanistic simulation model has been improved in two ways. First of all, three 22 underlying diseases causing lameness were modelled. This resulted in an estimated 23 economic impact of €31, €67 and €261 per case of lameness caused by digital 24 dermatitis, interdigital hyperplasia and hoof horn diseases, respectively. The 25 estimates differed for herds with different levels of diseases risk and reproductive 26 efficiency. Secondly, the existing simulation model was setup in way that it uses 27 hyper-distributions describing diseases risk of the three lameness causing diseases. 28 By combining information on herd-level risk factors with prevalence of lameness or 29 prevalence of underlying diseases among cows, marginal posterior probability 30 distributions for disease prevalence in the specific herd are created in a Bayesian 31 network. After transforming three parity specific disease prevalences into parity and 32 lactation stage specific risks of disease occurrence by calibration, random draws 33 from the distributions are used by the simulation model to describe disease 34 occurrence in a herd. Hereby uncertainty around herd specific risk is represented and 35 field data on prevalence is used systematically.