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

    Proposal summary:

    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 because of the associated costs of these measures. 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 is 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 and improved pasture condition helps maintain the ecologic and economic stability of the ranching operation.

    Project objectives from proposal:

    Western SARE Goals:

    1. Promote good stewardship of the nation’s natural resources by providing site-specific, regional and profitable sustainable farming and ranching methods that strengthen agricultural competitiveness; satisfy human food and fiber needs; maintain and enhance the quality and productivity of soil; conserve soil, water, energy, natural resources and fish and wildlife habitat; and maintain and improve the quality of surface and ground water.

    The information generated by this project will promote good stewardship of Hawaii’s range and pasture lands through a better understanding of how secondary compounds affect the foraging rate of grazing animals. With this information, producers will be able to implement targeted, behavior-based grazing programs that will increase the diversity of vegetation grazed, improve animal productivity and reduce the need and costs for herbicides. Increased productivity and reduced costs will result in more stable livestock operations in Hawaii.

    2. Enhance the quality of life of farmers and ranchers and ensure the viability of rural communities, for example, by increasing income and employment, especially profitable self-employment and innovative marketing opportunities in agricultural and rural communities.

    The knowledge gained from this project will lead to better managed range and pasture lands with greater forage production. This will lead to higher animal productivity and greater marketable product for ranches that adopt practices that result from this project. With better utilization of the ranch resources, lower costs of production, increased animal productivity and marketable product, these operations will be economically stable and important assets to their communities.

    3. Protect the health and safety of those involved in food and farm systems by reducing, where feasible and practical, the use of toxic materials in agricultural production, and by optimizing on-farm resources and integrating, where appropriate, biological cycles and controls.

    An important aspect of this project is its potential to provide a means to control invasive weeds without the use of costly herbicides. All classes of livestock have been shown to be effective at controlling weeds through targeted, behavior-based grazing practices. What is needed to effectively implement this type of grazing management though is a good understanding of the diversity of vegetation and secondary compounds that the plants contain. Thus the information compiled by this project will allow for producers to adopt targeted, behavior-based grazing practices.

    4. Promote crop, livestock and enterprise diversification.

    The information compiled by this project will be useful in determining the best class of animal to use when implementing targeted grazing plans. In some cases producers may be encouraged to incorporate sheep or goats into their cattle operations, while in other producers may begin to use land previously avoided because of the type of vegetation present. Either way, the producers will be using a greater diversity of forage plants.This will result in better stewardship and improved economic status of these operations.

    5. Examine the regional, economic, social and environmental implications of adopting sustainable agriculture practices and systems.

    This project will help producers in Hawaii become better stewards of their resources. Ultimately, this project will lead to economically stable livestock operations, healthy rural communities in Hawaii and healthy and productive range and pasture lands.

    Originality, distinctiveness, creativeness and innovativeness

    This project seeks to compile information on the content of secondary compounds on common range and pasture vegetation, including those commonly viewed as weeds. Currently no data or a resource exists that provides this information in a producer friendly format.

    This project will accomplish four objectives:

    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 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; and

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

    While plant databases, herbariums and field manuals all exist, these four objectives are completely unique in their focus on the content of secondary compound in range and pasture vegetation. Yet this information is extremely valuable to successfully implementing successful targeted, behavior-based grazing management plans. We believe that this project will result in the first databases, herbariums and field manuals that relate pasture forages to the secondary compounds that largely influence forage intake of grazing animals. As such, it will be an example for similar efforts in other regions.

    Timeline of activities and who is responsible

    At the beginning of the project the Principle Investigator (PI), Producers, Research Assistant (RA) and other project personnel will meet to compile a list of range and pasture plants to be included in the database. These plants will be common forage and weed species in Hawaii range and pasture lands. It is anticipated that this list will initially include approximately 50 plants. Once the list is compiled the PI and RA will begin developing a database referencing information from the literature on each plant. The database will contain information on secondary compounds, forage value, distribution and other pertinent data. This database will reveal gaps in our current knowledge about these plants and help focus our efforts to identify and quantify the secondary compounds they contain. The PI, RA and Producers will collect samples of plants identified for the database over the first two years of the project. These plant samples will be pressed, dried and mounted for inclusion in herbariums located in three of the county extension offices in the state. Additional plant samples will be collected to be analyzed for secondary compounds where the database indicates a gap in information. These samples will be dried and ground, or frozen, depending on the type of secondary compound being tested for. The samples will then be sent to appropriate laboratories for testing, including, but not limited to, the USDA-ARS Poisonous Plants Research Laboratory and University of California Agriculture and Natural Resources Analytical Laboratory. All data collected in compiling the database, field collections of plant samples, and analysis of samples for secondary compounds will be organized into a field manual beginning in the second year and completed in the third year. Fact sheets providing techniques for establishing targeted, behavior-based grazing management programs will be developed by the PI and RA. Workshops will also be developed and conducted during the third year, presenting producers with information on plant secondary compounds and behavior-based grazing management practices developed from this project.

    Description of the producers’ roles

    The three producers cooperating on this project will provide guidance in the development of the plant list for the project. Their input is essential in determining what information is important and how much is necessary to collect for each species. Moreover, since we cannot collect information on every plant in every pasture, the producers will help narrow the list to the most crucial species. The producers will also assist in the collection of plant samples and provide access for the PI, RA and other project personnel to collect plant samples during the three years of the project. All three producers are looking for alternatives to expensive herbicides in their pasture management programs. Two of the operations have established sheep and/or goat herds specifically for the control of weed and brush encroaching into their range and pasture lands. All three operations recognize the potential for their cattle herds to be used in the control of range and pasture weeds as well. However, they also recognize that since cattle are often more susceptible to toxicity, that a good knowledge of the distribution and quantity of secondary compounds in the vegetation is vital. Knowledge of the type and amount of secondary compounds found in the diversity of vegetation common to their pastures will help them make decisions on how best to target their grazing operations. This information will also help them determine how to use these various species in ways that will complement the animals diet and encourage increased intake of the targeted plants. For example, animals can be grazed in an area containing a high density of birdsfoot trefoil that contains moderate to high levels of tannin, followed by grazing an area infested with Madagascar fireweed, a plant that contains pyrrolizidine alkaloids. Grazing in this sequence would allow for the tannin to bind the alkaloid in the rumen of the animal and reduce the potential toxic effect on the animal. Scenarios such as this are possible for a number of plants. The key is to not over- or under-utilize the targeted plants; everything in moderation. Thus, information on the type and quantity of secondary compounds is needed to allow producers to make these kind of targeted management decisions and avoid situations that will discourage intake, or result in ingesting toxic levels. As the knowledge from this project is gained, the cooperating producers will be able to reduce their dependence on costly herbicides to control pasture weeds, they will increase the productivity of their pastures, and they will benefit economically with better animal production. Thus these producers will provide encouragement and a valuable example to other producers in the state of how targeted, behavior-based grazing management practices can improve pasture and economic returns.

    Educational products and outreach

    This project will result in a database listing common range and pasture plants in Hawaii along with their forage value, secondary compounds and other pertinent information. This database will be housed on the University of Hawaii at Manoa, Rangelands West website (http://rangelands.manoa.hawaii.edu/). Plant samples will be mounted and stored in three county extension office herbariums that will be available to the public for plant identification and educational purposes. A field manual will be produced that organizes the information learned in this project into a format usable for producers. The manual will provide pictures and text for field identification of plants, relative forage values and secondary compounds, and recommendations on utilization of the plants in a targeted grazing program. Finally, fact sheets providing information on developing targeted, behavior-based grazing management practices will be developed and distributed to producers in the state following the outreach plan.

    In the third year of this project a series of workshops will be provided to producers in Hawaii. These workshops will present knowledge learned from this project on plant secondary compounds in Hawaii and development of targeted, behavior-based grazing programs. Materials developed from this project, field manuals and fact sheets will be distributed through these workshops and other programs already on-going (spring and fall Stockman’s Field Day Educational Programs, Hawaii Grazing and Livestock Management Academy, etc.) through the University of Hawaii Cooperative Extension Service. Producers in the state will also be informed about access and use of the herbarium located in their counties. They will also be shown how to access and use the plant database online.

    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.