The manner in which plant phenolics determine dietary choices of ruminants and foragine strategies of ruminants govern the phenolic chemistry of plants will be investigated. Plants have adapted differently to the stresses of browsing and grazing ruminants. While the grazing interaction can be mutualistic, the browsing interaction is an evolutionary struggle of allelochemicals and detoxification pathways. Ecologically important allelochemicals in the browsing interaction include phenolics. This interdisciplinary study of the ruminant.phenolic interaction will involve feeding trials of captive deer and sheep, nutritional analyses of natural forages, and chemical investigations of plant phenolics and animal metabolism. The hypothesis that condensed tannins primarily affect nitrogen economy, while hydrolyzable tannins predominantly act as toxins will be tested. To test this hypothesis, the effects of tannins on grazers will be compared with the effects on browsers with emphasis on the role of salivary proteins in tannin detoxification. In addition, the effect of absorable phenolics on diet selection in ruminants will be explored. Rather than attempt to determine the metabolic fates of all phenolics, the phenolic profile of various plants using a simple fractionation scheme based on the polarity and solubility of phenolics will be established. Single forage feeding trials will be used to correlate phenolic profiles with intake suppression, and multiple forage feeding trials will be used to test the predictive power of our method. It is anticipated that with this scheme, it will be possible to predict which forages have complementary allelochemical profiles, and which will be selected as complementary dietary components by browsing ruminants.
