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Assessing toxicity of grassland/rangeland plants and their impact on livestock production and morbidity is an issue around the world. Tall fescue (Schedonorus arundinaceus Schreb.) is a naturalized grass species occurring on over 14 million ha in the USA with the majority infected with a fungal endophyte that produces ergopeptine alkaloids (primarily ergovaline). The objective of this paper is to show how an innovative pasture evaluation system at the University of Kentucky has been used to incorporate plan t toxicity information and species composition measurements to assess risk to livestock. Over the last 20 years over 500 horse farms have been intensively evaluated to determine total botanical composition and the ergovaline content of tall fescue present in pastures. Using various strategies, these measurements have been used to develop risk categories, which have then been communicated to the farms to enable stocking decisions. This project will establish sentinel farms that will provide additional inform ation on seasonal variability for ergovaline levels and the potential impact on livestock. This assessment strategy can be used to assess risk to livestock in many ecological regions around the world.