All data on diet-associated difference were analyzed by GLM procedure appropriate for completely randomized design(SAS, 2002). Broken-line regression analysis was employed using NLIN procedure (Robbins et al., 2006) and principal com-ponents analysis (PCA) was performed by PRINCOM procedure (SAS, 2002). Orthogonal polynomial contrasts were also usedto determine linear and quadratic responses of quail chicks to peppermint powder levels.