Quantifying Secondary Compounds in Common Pasture Vegetation for Behavior Based Grazing Management in Hawaii

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2009: $41,760.00
Projected End Date: 12/31/2012
Region: Western
State: Hawaii
Principal Investigator:
Dr. Mark Thorne
University of Hawaii at Manoa

Annual Reports


  • Animals: bovine, goats, sheep


  • Animal Production: feed/forage, animal protection and health, grazing management, grazing - multispecies, pasture renovation, range improvement, grazing - rotational
  • Education and Training: decision support system, extension, on-farm/ranch research, workshop
  • Pest Management: weed ecology


    This project was designed to quantify the plant secondary compounds in common forage and weed species found in range and pasture lands in Hawaii. The project developed a plant secondary compound database containing information on 40 species of plants. Specimens of these plants were collected, pressed, mounted and added to three herbariums housed in Kauai, Maui and Hawaii County Extension Offices. A field manual is being compiled, utilizing the information gathered in this project.


    Weed and brush encroachment into Hawaii’s range and pasture lands remains a significant problem affecting the sustainability of ranchers in the state. Herbicides and mechanical control measures, the common techniques for weed and brush control, are no longer economically viable options at the landscape scale. Many ranches are looking for alternatives to costly herbicides and mechanical control measures. Multi-species grazing has proven effective for some ranches. The introduction of sheep and/or goats into the grazing operation in most cases has produced dramatic results in the control of weeds and brush for these operations. Moreover, it has increased the diversity of product the ranch markets, improving the economics of their operations. Other producers are interested in the possibility of using their cattle as a means to graze range and pasture plants previously underutilized or avoided.

    Recent work by Dr. Fred Provenza and the BEHAVE group at Utah State University and others suggest that cattle and other animals can be trained and used to graze a greater diversity of plants in the pasture than previously thought. One critical issue to pursuing such a course is having an adequate understanding of the various plants available in the pasture system and the type and quantity of secondary compounds they contain, since it is these compounds that usually contribute to their low palatability and/or potential toxicity. Secondary compounds commonly found in range and pasture vegetation include alkaloids, tannins, phenols, terpenes and cyanide. Each of these compounds affects animals differently and is dependent on the relative concentration in the plant and the amount of plant ingested. Most of our understanding comes from, and is limited to, those plants known to contain toxic levels of these compounds. Yet at moderate levels, research has shown that these compounds may have benefits for grazing animals and, in some cases, may be complementary in the grazing diet. For example, tannins and alkaloids are found in several plants commonly grazed by livestock. Tannin may bind certain alkaloids in the rumen of the animal, reducing its toxicity.

    Currently, however, very little is known about how widespread these compounds are in the vegetation common to range and pasture lands. Thus, the purpose of this project was to compile and disseminate information on the type and quantity of secondary compounds found in the diversity of vegetation common to range and pasture lands in Hawaii. This information is important in helping Hawaii ranchers formulate more efficient grazing programs that will utilize a larger diversity of plants. Targeted grazing of many plant species previously underutilized or avoided because of the presence of these secondary compounds will provide for improved grazing utilization of pastures and greatly reduce the need of costly herbicides and mechanical control measures used otherwise. Better grazing utilization of pastures results in better control of weed and brush encroachment into pastures, increased livestock productivity, improved pasture condition and helps maintain the ecologic and economic stability of the ranching operation.

    Project objectives:

    The specific objectives for this project were:

    1) Develop an online database, accessible to the public, listing common range and pasture plants, their nutritional value, secondary compounds and recommended grazing practices for utilization.

    2) Establish a plant collection of the species in the database for identification and educational purposes that will be held in the Range and Pasture Plant herbariums, located at the county extension offices in Hawaii.

    3) Produce a field manual for producers and land managers providing information on the plants in the database that will be useful for field identification of the plants and will also provide a summary of secondary compounds, forage value, recommend targeted grazing practices and cautions for utilization of the plant.

    4) Develop targeted, behavior-based grazing practices for the plants in the database that will be presented in a series of fact sheets and extension service workshops.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.