An Incentive System for Salmonella Control in the Pork Supply Chain

producers under the three ownership structures when the threshold values are 1.5% or 1.0%. The
increased use of farm control package 2 is induced by a higher value of the producer penalty parameter.
Additional plant level control measures with acidification of slaughter equipment in cleaning and
disinfecting procedures are in effect for all presented Nash equilibrium cases⁵. For all ownership
structures, plant control package 2 is implemented before farm control package 2 becomes part of the
optimal solution.

The farm serological threshold level decreases to 10% when the bacteriological threshold level
falls to 0.5%, and the producer penalty remains high under all three ownership structures, inducing
producers to use farm control package 3. The producer quality premium increases to allow for the use
of farm control package 3 when the prevalence threshold value falls to 0.5 per cent. The cost
effectiveness of farm control package 3, with a high probability of a zero seroprevalence, is related to
the use of plant control package 3, with a probability of 100% for a zero bacteriological prevalence
when the seroprevalence is zero. Under all three ownership structures, plant control package 3 requires
that all herds are tested and associated parameter values are 0 for the production history indicator level,
1 for the maximum testing probability, and 0 for the testing probability reduction, thus making a static
incentive system optimal when the bacteriological threshold is 0.5 per cent. These expensive plant and
farm control measures prevent a dramatic increase in expected penalties and result in a lower expected
prevalence level. Expected welfare and monetary gains fall accordingly.

The optimal values of the production history indicator level, maximum testing probability,
testing probability reduction, producer penalty, and farm serological threshold are the same across all
three ownership structures when bacteriological threshold values are 3.5% or 3.0%. The optimal values
of the maximum testing probability and the optimal testing probability reduction parameter value are 0,
resulting in zero testing costs. The optimal performance of the incentive system is not affected by
⁵ Only for bacteriological threshold values higher than 5.5 plant control package 1 is part of the optimal solution.

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