A framework for decision support related to infectious diseases in slaughter pig fattening units Nils Toft a, * , Anders R. Kristensen a , Erik Jørgensen b a Department of Large Animal Sciences, The Royal Veterinary and Agricultural University, Grønnega ˚ rdsvej 8, DK-1870 Frederiksberg C, Denmark b Biometry Research Unit, Danish Institute of Agricultural Sciences, P.O. Box 50, DK-8830, Tjele, Denmark Received 25 April 2003; received in revised form 6 July 2004; accepted 16 July 2004 Abstract This paper analyzes the problem faced by managers of pig fattening units when the pigs are subject to common epidemic diseases, such as respiratory diseases or Swine Influenza. The problem is defined as a simultaneous optimization of the delivery policy and control strategies for disease control. As some disease controls, such as vaccination, are implemented at the batch level and last through the lifetime of the vaccinated pigs, the problem requires that deci- sions are addressed at multiple timescales. Using the framework of multi-level hierarchic Mar- kov processes a general framework was defined. The elements defining the framework were the decisions at the tactical (batch) level and the operational (daily) level. Decisions at the strategic level, e.g., decisions lasting longer than the length of a batch, were considered as constraints to the lower levels of the decision problem and not optimized. The major components of the gen- eral framework were a stochastic growth model, an epidemic model to handle within-batch spread of disease, a transition model to handle the between-batch spread of disease, and link between the growth model and the disease model and a general set of control measures. The model was illustrated using an example with Swine Influenza in an all-in-all-out production system. Results show that the optimal delivery policy and control strategies for disease 0308-521X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.agsy.2004.07.017 * Corresponding author. Tel.: +45 35283024; fax: +45 35283055. E-mail address: nt@dina.kvl.dk (N. Toft). www.elsevier.com/locate/agsy Agricultural Systems 85 (2005) 120–137 AGRICULTURAL SYSTEMS