Use of Fluorometry to Differentiate Among Clipped Species in the Genera Astragalus, Oxytropis, and Pleuraphis

A rapid and reproducible method to determine botanical composition of forage is an ecological and economic goal for range animal ecologists. Multidimensional fluorometry previously demonstrated the possibility of a unique optical approach for accurately determining species composition of clipped and digested plant materials. Fluorometry may be used to detect toxic plants in standing crop as well as diets by using electronic transitions in chemical structures at wavelengths between 370 and 580 nm. Grass hay (genus Pleuraphis) and 6 clipped forbs (4 species of Astragalus and 2 species of Oxytropis) were examined. The resulting spectral signatures were evaluated for differences in the blue and green regions of the visible spectrum using Principal Component Analysis (PCA). This represents the first published data using chemometrics to differentiate among fluorophores from these plant extracts. It was possible to distinguish between the grass and forbs and among forbs. Further research will be required to evaluate these same plant species in mixed diets and fecal samples.