Primary Roles for Plant Secondary Compounds: Enhancing the Health and Nutrition of Herbivores through Plant Biochemical Diversity.

Natural landscapes are diverse mixtures of plants that occur in a patchwork mosaic reflecting history of use in concert with soil, precipitation and temperature regimes. For plants, diversity is the rule for species, phenologies, growth forms and biochemistries. With regard to the latter, plants are nutrition centers and pharmacies with arrays of primary (nutrients) and secondary (pharmaceuticals) compounds (PSC)  which herbivores need for their nutrition and health. Plant secondary compounds like alkaloids, terpenes, and phenolics can benefit herbivores by, for instance, combating internal parasites, controlling populations of fungi and bacteria, enhancing nutrition and reducing oxidative stress. Herbivores are able to recognize some of these benefits and self-select feeds with bioactive compounds which contribute to restore homeostasis. Thus, the concepts of self-medication and forage biochemical diversity have the potential to pioneer the design of sustainable grazing systems which improve the quality of land as well as the health and welfare of animals.