Theses and Dissertations

Issuing Body

Mississippi State University


Wills, Robert W.

Committee Member

Jack, Sherman W.

Committee Member

Bailey, R. Hartford

Committee Member

Huston, Carla L.

Committee Member

To, Filip Suminto D.

Date of Degree


Document Type

Dissertation - Open Access


Veterinary Medical Science

Degree Name

Doctor of Philosophy


College of Veterinary Medicine


Veterinary Medical Science Program


Salmonella has been studied and researched for more than a hundred years and yet it remains a problem for human and animal health. The goal of this dissertation was to apply the systems thinking approach to Salmonella contamination and develop a System Dynamics (SD) simulation model for Salmonella contamination in the chill tank of a poultry processing plant. But first the appropriate carcass rinse sampling method that would not impact on the resulting Salmonella contamination status of the broiler carcass was studied. Kappa agreement analysis was used to evaluate three sampling methods. The adjacent rinse method was found to be the best method. In the absence of actual data, literature data was used to develop a literature-based SD simulation model of Salmonella contamination of broiler carcasses in the chill tank. The literature-based SD model is the first application of system dynamics simulation modeling in the poultry-processing field. The model was able to show and simulate the dynamic and non-linear interrelationships between parameters, namely pH, chlorine (Cl) level, water flow and turbidity. Actual data collection was done using a specially designed apparatus that recorded the time, temperature, pH, chlorine, water flow and turbidity in the chill tank as carcass rinse samples were collected. Linear regression analysis was used to identify the statistically significant models for relationships between the parameters in the chill tank. Finally, the data was analyzed using logistic regression to determine the association between the parameters in the chill tank and the occurrence of Salmonellaa in carcasses exiting the chill tank. These results were used to develop a data-based SD model. The data-based model was then validated using the validity tests proposed by various authors for SD simulation models and found to be a valid model. The developed model offers a fresh perspective to the problem of Salmonella contamination- to view it as a system of factors that are interrelated and have a feedback mechanism, rather than the traditional concept of linear causation. The developed model is a powerful cost efficient tool for testing interventions for reducing Salmonella contamination in the poultry processing plant.



STELLA model||system dynamics||Salmonella contamination||carcass rinse