Goats and sheep consider some of these palatable (greenbriar, poison ivy, Virginia creeper) while others are browsed only when choices are limited (mesquite, nightshade, cedar).

We cannot study all of these, but we are targeting some of the most troublesome:

Honey Mesquite (Prosopis juliflora var. glandulosa): can it be controlled both as young saplings and older trees? Are there toxins contained in the leaves that affect goats negatively when they are forced to graze mesquite under pressure?

Greenbriar (Smilax sp.) can overwhelm the lower canopy of hardwood forests and create elaborate vine communities up hardwood trunks. Can goats consume the greenbriar despite the numerous thorns and spines found on its stems and leaves? How does grazing greenbriar below the browse line affect growth of greenbriar above the browse line? Does grazing by goats impact mechanical control methods or herbicide application?

Notice the thorns around the leaf margin and on the stem of the saw greenbriar. Although there are thorns on the stems and leaves of common greenbriar, they are not as numerous or long as saw greenbriar thorns and do not keep goats from plucking them.

Questions currently being addressed with goat ISDGB trials:

What is more effective in greenbriar control: stocking rates or duration?

Studies to answer this question began in June, 2005 at the Texas Agricultural Experiment Station (TAES) in Stephenville, Texas. Ten acres of dense hardwood forest were sectioned into 10 paddocks of approximately 1 acre. Eight paddocks were used in the study. Four to six month old Spanish x Boer goat whethers were introduced into the paddocks at three different stocking rates: 5 goats/acre (low), 10 goats/acre (medium) and 15 goats/acre (high). Goats were allowed to graze on the paddocks for a minimum of 30 days or until edible herbage was reduced to 5% or less.

In addition to questions about stocking rates, mechanical clearing and herbicide effectiveness are also being tested.

Prior to releasing the goats, brush growing above the browse line (set at approximately 5 feet) was hand cleared or cut in half of each paddock. Herbicide (15% Remedy, 85% diesel fuel) was applied to greenbriar after the goats were removed from the paddocks at three different times; 10 days after the goats were removed from the paddock area, immediately (within 5 days) after the first light frost, and mid-winter after several heavy frosts had induced dormancy in the greenbriar.

Goats must have access to vegetation in order to control it. Mechanical cutting of brush at the browse line kills everything above, while goats eat everything below. Unwanted hardwood species as well as vines were cut.

Preliminary Results from the First Year of Our Study (2005)

Stocking rates do make a difference!!! In the above picture, the left side of the fence represents a paddock with low stocking rate and the right side of the fence represents a paddock with medium stocking rate. Both paddocks have been grazed for the same amount of time but the low stocking rate still has a considerable amount of brush left in it!!! Both the medium and high stocking rates showed dramatic reduction of brush (between 95-100%) after 30 days of grazing. To produce the same results with the low stocking rate required 20 to 30 more grazing days. All goats lost weight during the study, regardless of stocking rates.

Just how much difference do the goats make in 30 days?

The right side of the fence is a control paddock which was left ungrazed. The left side of the fence had a high stocking rate of goats for 30 days (both photos). The entire bottom half of the photo on the left, up to the hardwood trees, is covered with bare greenbriar stems. The photo on the right is a mixture of greenbriar and grass up to the hardwood line.

. . .HOWEVER. . .

Greenbriar recovers very quickly. This is regrowth after only 1 week without goats!!

Herbicide application, in addition to goat grazing, may increase the amount of greenbriar that can be controlled.

Herbicide was applied in both the grazed (left) and the ungrazed (right) paddocks. Evaluation of all herbicide applications looked very promising this spring (2006). However, it should be noted that north central Texas has been experiencing extreme drought conditions and some of the control could be due to the lack of rainfall rather than herbicide application. More herbicide trials will be conducted and monitoring will continue.

Does palatability of resprouting mesquite change with season of clearing or herbicide application?

A study to answer this question has been set up in Brown County, Texas. Approximately 24 acres of dense mesquite will be intensely grazed by 60-70 goats for 30 days beginning in late July-early August. We are also incorporating hand clearing of mesquite prior to grazing and herbicide application in addition to grazing to see how goats affect these traditional control methods. The first clearing and herbicide application was done in April, 2006. These will continue every 3 months for the duration of the study.