Risico en economie van insleep van ziekten op melkveebedrijven.

A well closed farming system will enhance the success of disease eradication programs, because introduction or reintroduction of infectious diseases are less likely. The economic implications of a more closed farming system will not always been obvious for farmers. The management decisions need to be made for different parts of the farm and are farm-specific. The objective of the study was to obtain input for and to develop an on-farm decisions support model to calculate the economic consequences of a more closed farming system. The input was based on IBR, since there were numerous data on this disease, but a more closed farming system will prevent introduction of other diseases as well (i.e. Bovine Virus Diarrhoea Virus (BVDV), Leptospira interrogans serovar hardjo (L. hardjo) , and Salmonella enterica subsp. enterica serotype Dublin (S. dublin) ). Direct animal contacts such as purchase of cattle, participating in cattle shows, and cattle that breach or escape and mingle with other cattle were found to be important risk factors for introduction of Bovine Herpesvirus type 1 (BHV1). Furthermore, the use of protective farm clothing was found to be an important preventive factor. The effect of a BHV1 outbreak on milk production was estimated with a random effect model. An outbreak of BHV1 on a BHV1-free farm, caused limited milk production losses of on average 39 kg per cow during the outbreak, but the variability was high (95% CI 1-77 kg). Nine percent of Dutch BHV1-free dairy farms that were also at risk for BVDV, L. hardjo and/or S. dublin had one introduction per year of one of these four diseases. All these results were incorporated in the static, deterministic economic model. The management measures to reduce the probability of introduction of BHV1, the costs of these measures, and the risk reduction of these measures were obtained from other sources. Costs were calculated by using partial budgeting. The model was verified and partly validated and a sensitivity analysis was carried out to obtain insight into the model behaviour. A hypothetical 55-cow dairy farm that refrained from purchasing cattle, provided protective clothing to professional visitors and a temporary worker, and placed a double fence on six ha. of land to prevent over the fence contacts, had to spend Dfl. 4495 in five years. The probability of disease introduction was decreased by 74%. The avoided losses for disease introduction amounted to Dfl. 7033 over five years. The benefit of becoming more closed for this hypothetical farm was Dfl. 2538. The implementation of a more closed system will be profitable for most farms. The profitability will increase when a farm is at risk for more diseases, but will decrease when farms are limited in their facilities to rear replacement heifers or when a large amount of pasture adjoins pasture of other cattle farms.