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United States Department of Agriculture

Agricultural Research Service

Research Project: THE TOXICITY OF PYRROLIZIDINE ALKALOID-CONTAINING PLANTS AND OTHER HEPATOTOXIC AND NEUROTOXIC PLANTS

Location: Poisonous Plant Research

Title: Value of Plant Diversity for Diet Mixing and Sequencing in Herbivores

Authors
item Provenza, Frederick - USU
item Villalba, Juan - USU
item Wiedmeier, Randy - USU
item Layman, Tiffanny - USU
item Owens, Jake - USU
item Lisonbee, Larry - USU
item Clemensen, Andrea - USU
item WELCH, KEVIN
item GARDNER, DALE
item LEE, STEPHEN

Submitted to: Rangelands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 7, 2009
Publication Date: February 1, 2009
Repository URL: http://www.bioone.org/doi/pdf/10.2111/1551-501X-31.1.45?cookieSet=1
Citation: Provenza, F.D., Villalba, J.J., Wiedmeier, R.W., Layman, T., Owens, J., Lisonbee, L., Clemensen, A., Welch, K.D., Gardner, D.R., Lee, S.T. 2009. Value of Plant Diversity for Diet Mixing and Sequencing in Herbivores. Rangelands. 31(1):45-49. DOI:10.2111/1551-501X-31.1.45

Interpretive Summary: Agronomists and ecologists alike have come to view plant secondary compounds as defenses against herbivory because secondary compounds limit intake. Thus, we know little about how herbivores might benefit from secondary compounds. The outcomes of all biochemical interactions depend on the dosage: nutrients and secondary compounds at high dosages can be toxic, but at low dosages they have health benefits. Herbivores can meet their nutritional needs by eating a variety of complementary plants, and combinations of secondary compounds may more effectively reduce bloat and internal parasites, especially if animals learn to self-medicate on diverse mixtures of plants. Diet mixing and diet sequencing enable herbivores to increase their dietary breadth and consequently the amount of plant secondary compounds consumed without toxic effects. These results are probably due to complementary relationships among secondary and primary compounds in the grasses and legumes that enable herbivores to eat more of a combination of foods than of only one food. Collectively, these findings suggest that herbivores regulate intake of plants as a function of interactions between secondary compounds and that the sequence in which they eat forages is crucial for increasing their intake of plants that differ in secondary compounds. Growing realization of the roles of secondary compounds in ecological systems reveals that they must be considered just as much as primary compounds in the behavior of soil, plants, herbivores, and people. We also must begin to create databases that describe what is known about possible complimentary and non-complimentary interactions among secondary compounds, their interactions with primary compounds, and their benefits in nutrition and health at appropriate dosages. This information will enable people to manage grazing on landscapes in ways that enhance our ability to produce domestic and wild herbivores, reduce the abundance of weeds, and use livestock to rejuvenate landscapes.

Technical Abstract: All plants contain secondary compounds that, at high concentrations, limit how much of any food an herbivore can eat. Herbivores regulate intake of secondary compounds to ingest adequate levels of nutrients and to avoid toxicosis. Eating a variety of foods is the best way to accomplish this objective, because different secondary compounds are processed at different rates via different metabolic pathways, thereby providing multiple avenues for detoxification. Variety is so important that animals have built-in mechanisms to ensure that they eat a variety of foods and that they forage in different locations. Offering animals choices on pastures and rangelands allows each animal to meet its needs for nutrients and to regulate its intake of secondary compounds by mixing foods in ways that work for that individual. Thus, variety enables individuality and greatly increases the likelihood of providing cells with the vast arrays of primary and secondary compounds essential for their nutrition and health. Conversely, monocultures of plants high in secondary compounds, produced through inappropriate grazing practices can create vicious cycles that escalate, to the detriment of soil, plants, herbivores, and people. We discuss how diet mixing and diet sequencing enable herbivores to increase their dietary breadth and consequently the amount of plant secondary compounds consumed without toxic effects. Growing realization of the roles of secondary compounds in ecological systems reveals that they must be considered just as much as primary compounds in the behavior of soil, plants, herbivores, and people. We must begin to create databases that describe what is known about possible complimentary and non-complimentary interactions among secondary compounds, their interactions with primary compounds, and their benefits in nutrition and health at appropriate dosages. This information will enable people to manage grazing on landscapes in ways that enhance our ability to produce domestic and wild herbivores, reduce the abundance of weeds, and use livestock to rejuvenate landscapes.

Last Modified: 9/10/2014