Despite its worldwide presence, the characteristics of dairy industry may vary largely from one country to another and also between the different regions of a country. Farmers can form co-operatives or operate individually, while processors may transform very different amounts of milk into a diversity of dairy products. Moreover, the variety of dairy products that can be found in the market, the short-term expiry date of some of them, as well as the strong competition for a saturated market, lead to a complex environment, where the design and operation of the dairy factories require decision support tools for helping the decision makers. In this paper, it is considered the development of a decision support system for improving the survival chances of dairy plants in a competitive worldwide market. This tool is based in the implementation of an optimization process, where the performance evaluation of the feasible decisions is performed by means of simulation. The objective of the decision making covers the complete life cycle of the dairy plant from its design to its operation.