1.In poultry investigations, the main interest is to study the effects of many factors simultaneously. Two or three level factorial designs, are the most commonly used experimental design for this type of investigation. However, it is often too costly to perform while number of factor increase. So a fractional factorial design, which is a subset or fraction of a full factorial design, is preferred. Taguchi method has been proposed to simplify and standardize the fractional factorial design. 2.An experiment was conducted to evaluate the applicability of the Taguchi method to optimize in vitro intrinsic phytase activity (IPA) of rye, wheat and barley under different culture conditions. 3.In order to have a solid base for judging the suitability of the Taguchi method, the results of the Taguchi method were compared with those of an experiment that was conducted as a 34 full factorial arrangement with three feed ingredients (rye, wheat and barley), three temperature (20, 38 and 55 ◦C), three pH levels (3.0, 5.5 and 8.0) and three incubation times (30, 60 and 120 min), with two replicates per treatments. 4.After data collection, a Taguchi L 9 (34) orthogonal array was used to estimate the effects of different factors on the IPA, based on a subset of only 9 instead of 81 treatments. The data were analyzed with both Taguchi and full factorial methods and the main effects and the optimal combinations of these four factors were obtained for each method. 5.The results indicated that according to both the full factorial experimental design and the Taguchi methods the optimal culture conditions were obtained with the following combination rye - pH=3 - temperature=20 ◦C and time of incubation=30 min. The comparison between the Taguchi and full factorial results showed that the Taguchi method is a sufficient and resource saving alternative to the full factorial design for optimization of several factors in poultry science.

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