Training Livestock to Eat Weeds in the Tropical Pacific and Evaluating the Effects on Meat Quality for Stronger Ranch Profits

2013 Annual Report for OW11-309

Project Type: Professional + Producer
Funds awarded in 2011: $49,610.00
Projected End Date: 12/31/2014
Region: Western
State: Hawaii
Principal Investigator:
Matthew Stevenson
University of Hawaii

Training Livestock to Eat Weeds in the Tropical Pacific and Evaluating the Effects on Meat Quality for Stronger Ranch Profits


The purpose of this university-ranch collaborative demonstration project is to evaluate a North American-developed approach to train livestock to eat pasture weeds in a tropical environment. Training cattle, sheep and goats to eat previously avoided pasture weeds at least briefly in a test pen has, by and large, been successful at four ranches. We continued to monitor established sites at two ranches and set up short-term monitoring sites at a third. Most sites showed modest changes in weed and dominant species cover or density to date. Several sites have low stocking densities and weed populations are patchy. Under these conditions, it has been difficult to tell if the lack of weed patch expansion has been due to grazing pressure, competition with dominant pasture species or some environmental response. 

In 2013, we modified monitoring as per our last report from a quarterly to twice annual basis. Also, we conducted one intensive management trial at Haleakala Ranch, Maui, as per the modification suggested in the last report. The intensively managed project targeted Leonotis nepetifolia and Digitaria insularis for control, using energy supplements and increased stocking density or numbers of animals per land area. Haleakala Ranch has adopted the concepts of training livestock to eat weeds and is adapting the methods to meet their needs. Preliminary results were presented at one professional meeting and two producer conferences. The response has been generally positive in accepting the project concept and methodology. A no-cost extension was requested to enable data collection for beef taste and compositional analysis. Circumstances outside the PI’s control prevented collection of beef samples from the project for analysis.

Objectives/Performance Targets

Objective 1: Trained cattle, sheep and goats will consume unfamiliar foods.

Since the project start, cattle have been trained and observed to eat Schizachyrium condensatum (Jurassic Kahili Ranch – Kauai), Sphagneticola trilobata (Rocking W Ranch – Kauai), Amaranthus spinosa (Haleakala Ranch – Maui) and Leonotis nepetifolia (Haleakala Ranch). Goats have been trained to eat Asclepias physocarpa (Haleakala Ranch) and S. trilobata (Tom’s Goats – Kauai) but were only observed to eat the latter.  Sheep were trained and observed to eat Elephantopus mollis (Jurassic Kahili Ranch) and L. nepetifolia (Haleakala Ranch).

As per the modifications suggested in the previous annual report, we trained cattle, sheep and goats in 2013/2014 to eat sour grass (Digitaria insularis), lion’s ears (L. nepetifolia) and avocado (Persea americana) at Haleakala Ranch (Maui). Methods and results of these efforts are discussed in the Accomplishments/Milestones section.

Objective 2: Livestock offered a free-choice diet supplement of tannins, terpenes, protein and energy will be able to consume weeds with high levels of secondary compounds.

In 2013 – 2014, we supplemented livestock with grain and molasses as energy supplements in an attempt to increase intake on avocado, sour grass and lion’s ears. Results are discussed in the Accomplishments/Milestones section.

Objective 3: Targeted weed populations will decrease with increasing grazing pressure from trained livestock.

We continued long-term monitoring plots at the remaining sites: Kapapala Ranch (Hawaii), Rocking W Ranch (Kauai) and Jurassic Kahili Ranch (Kauai). Short-term photo monitoring sites were established at Haleakala Ranch (Maui).         

Objective 4: Effects of consuming weeds on meat quality will not be detectable.

Due to unprecedented drought, beef animals at Haleakala Ranch went to slaughter before samples could be collected for analysis. Beef animals that were trained onto weeds on Kauai were retained as replacements and did not go to market. A no-cost extension was requested so that this important part of the project may be completed with a newly trained set of beef cattle, should any be available.


Objective 1

In September 2013, Haleakala Ranch trained three heifers, 10 sheep and 10 goats to eat an unknown variety of avocado using a truncated version of the training method over three days. In December, we trained this group to eat lion’s ears. A variant of this training was used to test the intake of sour grass (Digitaria insularis) among a mob of 400 cattle and is also described below.

Objective 2

Haleakala Ranch (Maui) – We modified the training method described in the proposal to shorten the period to three days and used grain as both an energy supplement and positive experience for the animal in eating something new or avoided.  In September, three heifers, 10 sheep (mixed sex) and 10 goats (mixed sex) were penned and fed grain together as part of a separate bonding project. Avocado leaves were also introduced when the animals were fed. The Merck Veterinary Manual lists avocado as toxic to livestock; however, these animals had free access to pasture and could mix their diet, possibly minimizing adverse effects. Informal observation revealed that all species preferred to eat avocado leaves when first let into the pasture containing the tree. All species ate old leaves, fresh leaves and fruits with no apparent toxicity issues.

In another variant of the livestock training, in December, we used straight molasses as an energy supplement and enticement for this group to eat lion’s ears. The above mixed group of livestock was put on a small three acre paddock. Each afternoon for three days they were offered a supplement of lion’s ears drizzled with approximately a pint of molasses. Livestock ate most of the lion’s ears offered in the trough, and initial photo monitoring and inspection showed they ate lion’s ears in the pasture without any molasses added. We will continue photo monitoring over time to see impacts on the lion’s ears stands.

The molasses approach was also used to train cattle to increase intake of sour grass. Sour grass is usually left untouched by cattle in a rotational grazing system. Four hundred cows and heifers were let into a three acre paddock heavily infested with sour grass that had been partially sprayed with a diluted molasses mixture. After 12 hours the cattle were moved out, with significant sour grass use in both sprayed and unsprayed areas. Increasing stock density while offering an energy supplement appears to increase intake of sour grass in cattle. This method also increased intake of another group of 100 head in a 20 acre paddock with small patches of sour grass. Cattle ate patches of both sprayed and unsprayed sour grass where before none would be eaten. 

Objective 3

Kapapala Ranch – Figures 1 and 2 shows very little change in guava and myrica faya densities at the Kapapala sites in 2013. Several myrica faya bushes showed signs of limited or light browsing.

Rocking W Ranch – Ranch managers selected Sphagneticola trilobata (wedelia) for control with conditioned preference training of cattle. Three 50 m long line-point transects were established at each of four sites with S. trilobata present. S. trilobata, a strongly stoloniferous and rhizomatous forb, can form dense, monotypic stands after establishment. Monitoring in 2013 showed little change in previous trends as shown in Figure 3.

Jurassic Kahili Ranch – Ranch managers identified Schizachyrium condensatum (bushy beard grass) to be controlled with cattle and Elephantopus mollis (soft elephantsfoot) to be controlled with sheep. Four monitoring sites (two sites per target weed species) were established using the same line-point transect method to estimate percent cover. S. condensatum is a perennial bunchgrass of very poor forage quality and palatability to cattle and sheep that can form monotypic stands. E. mollis tends to form dense patches in sod-forming forage types. Like S. trilobata sites at Rocking W, the monitoring sites were chosen in areas with currently low cover to note any increase. Figure 4 shows both species’ cover remained low during the study period to date.

Impacts and Contributions/Outcomes

While the data do not show dramatic changes in monitoring sites, collaborating producers were glad to see no increase in target weeds. Also, in 2013, a project introduction and preliminary results were presented at two producer meetings and one professional meeting. Logistics of two of the meetings prevented collection of formal evaluations, while the third was collected via online survey based on the SARE post-workshop evaluation form. On September 26, 2013, the PI gave a talk on the concept, training method and preliminary results of the project to an Extension professional workshop held at the Poamoho Experiment Station of the University of Hawaii. Owing to different groups going to multiple field visit sites immediately after the talk, most participants left before any formal data could be collected. However, the questions and comments during the talk indicated interest in promoting this approach for weed control when meeting with clients. On November 8, 2013, the PI presented a talk accompanied with slides to the Hawaii Sheep and Goat Association annual meeting attended by 28 people. Post-presentation evaluation data were collected via online survey and are summarized in Figure 5.

From November 15 – 16, 2013, the PI and one collaborating rancher were present at the College of Tropical Agriculture and Human Resources (CTAHR) booth with a looped computer presentation on the project. In this informal setting, it was difficult to collect formal evaluations, but of the approximately 200 attendees, many visited the booth and asked questions about the project. A formal presentation is being prepared for the CTAHR Stockman’s Spring Field Day in April 2014.

Very encouraging to the PI was that one collaborating ranch, Haleakala Ranch, has adopted the concepts and practices of training livestock to eat weeds (Figures 6, 7a & b, 8a & b). As reported above, the ranch is adapting the techniques to meet their needs more efficiently. This is a significant impact as this ranch runs several thousand head of cattle, sheep, goats and poultry on over 30,000 acres. Other ranches on Maui learn about their practices at the Maui Cattlemen’s Association and frequently adopt similar approaches.


Dr. Yong Soo Kim
University of Hawaii
1955 East-West Rd.
Honolulu, HI 96822
Office Phone: 8089568335
Dr. Juan Villalba
Research Professor
Utah State University
5230 Old Main Hill
Logan, UT 84322
Office Phone: 4357972539
Dr. Ashley Stokes
Extension Veterinarian
University of Hawaii
1955 East-West Rd
Honolulu, HI 96822
Office Phone: 8089568961
Lani Petrie
Ranch Manager
Kapapala Ranch
P.O. Box 1639
Hilo, HI 96721
Office Phone: 8089286202
Greg Friel
Livestock Manager
Haleakala Ranch Company
529 Kealaloa Ave.
Makawao, HI 96768
Office Phone: 8085721500
Dr. Mark Thorne
Range Extension Specialist
University of Hawaii
67-5189 Kamamalu Rd.
Kamuela, HI 96743
Office Phone: 8088876183
Dr. Fred Provenza
Professor Emeritus
Utah State University
5230 Old Main Hill
Logan, UT 84322
Office Phone: 4357971604
Duke Wellington

Rocking W Ranch
P.O. Box 356
Eleele, HI 96705
Office Phone: 8086398088
Randall Cremer
Ranch Manager
Jurassic Kahili Ranch
P.O. Box 739
Kilauea, HI 96754
Office Phone: 8086396503
Tom Runyan
Tom's Goats
P.O. Box 869
Kapaa, HI 96746
Office Phone: 8088221566