Development of a milk quality assurance program for paratuberculosis: from within- and between herd dynamics to economic decision analysis

A new surveillance program was developed that guarantees a certain maximum number of Map bacteria per litre of bulk milk. In the new program dairy herds are distinguished in two categories, 'green' and 'red', where 'green' stands for the pool of certified herds which guarantee a preset bulk milk quality. The program is based on 3 parts: (1) an intake-procedure (certification), (2) a surveillance-procedure to monitor 'green' herds, and (3) a control-procedure on 'red' herds. Models were developed to study the development in time of the group of 'green' herds and of the group of 'red' herds (size, prevalence, MAP in bulk milk). Several test regimes (based on blood or faeces tests) were combined with absence or presence of management measures and of purchase of animals. Results of epidemiological models were used in an economical decision analysis. Results were as follows. It is very important for 'green' herds to exclude animal trade. Management measures are less important during the first 8 years, but are very important on 'red' herds. The intake- and surveillance test scheme itself is less important than presence or absence of animal trade and of management measures. However, on 'red' herds the control test scheme does matter. Only if a milk price differentiation for milk produced by 'green' herds is introduced, the 'green' herds will join the program. The majority of all dairy herds in the Netherlands will be certified as 'green' after intake. When a farmer receives a 'red' status, the preferred decision is to stop immediately joining the program even if the milk price differentiation is ¿ 0.01 per litre milk. This will happen with 10-14% of the herds, which will become 'red' immediately after the intake procedure, and with herds tested positive during the following surveillance procedure.