Sustainable and profitable control of invasive plant species by small ruminants

Project Overview

Project Type: Research and Education
Funds awarded in 2005: $178,000.00
Projected End Date: 12/31/2009
Region: Southern
State: Texas
Principal Investigator:
Dr. James Muir
Texas A&M AgriLife Research

Annual Reports


  • Additional Plants: native plants


  • Animal Production: pasture renovation, range improvement
  • Education and Training: demonstration, extension, farmer to farmer, focus group, on-farm/ranch research, participatory research, workshop
  • Farm Business Management: new enterprise development
  • Natural Resources/Environment: biodiversity
  • Pest Management: biological control, weed ecology
  • Production Systems: holistic management


    Overgrazed rangeland and invasion of aggressive vegetation in disturbed land are environmental concerns in the southeastern USA, St. Croix, and Puerto Rico. This project addressed plant:animal interface concerns that contribute to resolving both issues by expanding the use of small-scale commercial flocks (goats and sheep) to control invasive weeds. How this is done effectively, on what species and at what cost was addressed in five representative locations throughout the southern SARE region: Puerto Rico, St. Croix, Florida, Georgia and Texas. Defining and refining intensive, short-duration goat/sheep browsing (ISDGB) techniques for controlling weeds was the goal. The experiments, presentations, field days, demonstrations, and publications produced should encourage the commercialization of ISDGB by small ruminant farmers and managers of land with invading vegetation.

    Puerto Rico

    In Puerto Rico, invasive weed species reduce forage availability in tropically grazed pastures by over 50%. On alkaline and dry sites, Leucaena (Leucaena leucocephala Lam. De Wit) form thickets and limits grass growth. Invasive legume weed species on wet sites include White acacia (Albizia procera), climbing mimosa (Mimosa casta) and catclaw (M. pellita; formerly M. pigra). Mature trees of albizia can be eradicated with ISDGB in a one-year-period. Catclaw will require mechanical cutting as very little is consumed by goats. Younger resprouts can be maintained at acceptable levels in pastures with ISDGB. Climbing mimosa can be eradicated with ISDGB, but the short dry period in these areas will pose a challenge. Minimizing leucaena in thick stands will require mechanical maintenance (1 cut per year), followed by intensive stocking with goats. In conclusion, ISDGB is an alternative to chemical control of invasive species in the Caribbean basin.


    In Georgia and much of the southeastern United States, kudzu (Pueraria lobata), a drought-tolerant, perennial warm-season vine, was once considered an important forage plant for grazing animals, but is now classified as a weed species, often choking out other vegetation with its climbing growth habit and large leaves. Both goats and sheep readily consume kudzu forage, and its leaves maintain high levels of crude protein (>20%) throughout the grazing season, suggesting its use as a source of feed. Its growth can be controlled through ISDGB in areas where it is not wanted, although the length of time needed to achieve total eradication is still to be determined.


    Perennial peanut, a nitrogen-fixing legume, is planted under fruit trees in Florida orchards. However, invasive weeds are difficult to control in this herbaceous, mat-forming species. The use of sheep in ISDGB systems was tested with mixed results. When rainfall is good, weed growth outpaces ISDGB suppression whereas when rainfall is low, sheep tend to eat too much of the perennial peanut. Further refinement of the system is needed.


    Greenbriar (Smilax spp.) suppression was targeted in wooded areas using goats in ISDGB. Results indicate that eradication is not permanent with this deep-rooted perennial vine although better results occur when vines are initially cut below the browse line to make regrowth accessible and when higher stocking rates are used. Mesquite (Prosopis juliflora var. glandulosa) eradication is not achievable using ISDBG because goats do not browse it sufficiently, even when it is mechanically cut at ground level to bring regrowth within browse reach.

    St. Croix

    Throughout the Caribbean Basin, the ornamental exotic, coral vine (Antigonon leptopus), has become an invasive weed. ISDGB on-farm and on-station indicate that St. Croix sheep will consume both leaves and vines of this deep-rooted perennial and suppression (but not permanent control) is possible, providing access to land that was densely invaded that no other agricultural use was possible.

    Project objectives:

    1) Develop ISDGB trials that address flock owner/landowner questions and serve as local demonstrations of this method for environmentally sustainable invasive plant control.

    2) Research specific plant:animal interface issues that will develop into the techniques that effectively control of permanently eradicate invasive plants in each environment and for each species, including stocking rates, seasonal vulnerability, browsing duration, and negative effects on both native vegetation and flock performance.

    3) Develop farmer-to-farmer contacts, demonstrations, brochures, popular press articles, web pages, and refereed articles to foment greater commercial application of ISDBG in the region.

    4) Assist both landowners and goat/sheep flock mangers in determining equitable cost sharing for the commercial application of ISDGB.

    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.