The Use of an Electronic Spreadsheet to Solve Linear and Non-Linear “Stochastic” Feed Formulation Problems

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Abstract
Typical linear programming models used by the feed industry for ration formulation include no features to account for variability in ingredient composition. Average composition values are input; therefore, the confidence in meeting nutrient restrictions is 50%. Commercial feed formulation software is available that contains non-linear “stochastic” models capable of meeting nutrient restrictions with any specified level of confidence. Such stochastic models require mean and variance values for the nutrient composition of each ingredient. Commercial stochastic programming software was offered for sale in the Spring of 1997 for $18.000. We show here how to solve the problem with spreadsheet software available for personal computers at a cost of under $300 (<$50 at our campus purchasing department). While the spreadsheet is not as powerful as the commercial software in some respects, it is capable of giving the correct answer to stochastic feed formulation problems. The models presented herein should be useful in teaching and research. They can also formulate a limited number of rations where more sophisticated commercial software is not necessary. This software is available on the World Wide Web.