Woodland Steward Prescribed Grazing Article (Part 2) 

By Ron Rathfon

. . . And so we return to my original story of trying to control multiflora rose in a woods at SIPAC and the dayFigure 1. Goats are well-adapted to both grazing and browsing on woody vegetation. Portable grazing system fences such as this electric netting make prescribed grazing feasible in forest environments and on rough terrain. the goats arrived. 

My colleagues Songlin Fei (Purdue Forestry & Natural Resources), Mike Neary (Purdue Animal Science), Ken Andries (Kentucky State University animal scientist), and Jason Tower (SIPAC manager) and I began addressing some of the questions just raised about prescribed grazing by conducting an experiment in the multiflora rose woods. The objectives of this study were to test grazing intensity (low and high goat stocking rates) and two grazing frequencies within a growing season using goats to reduce multiflora rose and to quantify impacts of those treatments on non-target native vegetation, including hardwood tree regeneration. By the time grazing started in May 2012, multiflora rose had fully recovered from our earlier attempts to burn it out, averaging 6 ft. tall and covering 56% of the forest floor.  Our experimental treatments were:

•        Control, or no treatment

•        Manual cutting + herbicide

•        Low stocking with two grazings

•        Low stocking with one grazing

•        High stocking with two grazings

•        High stocking with one grazing

Goats assigned to the project were mature does that were open (not pregnant) and not lactating (no kids). The goats were meat goats provided by the existing herd at SIPAC and from a Kentucky State University herd. They were a relatively hardy, self-sustaining cross-breed of Boer, Kiko, Savanna, and Spanish influence. Paddocks were fenced using portable electric netting.

Goats are considered generalists (Figure 1), meaning they eat just about anything green.  In fact, “prescribed grazing” may be a bit of a misnomer since goats not only graze on leaves, but also browse woody stems.  In the case of multiflora rose, the newest, most tender and succulent leaves and shoot tips located at the goats head level were first grazed and browsed. When that was gone, the goats stretched their necks a little higher. Finally, expending more energy, goats stood on hind legs to reach more woody stems or work harder to penetrate to the interior of dense rose thickets using their long, slender muzzles and prehensile, yet amazingly tough, tongues and lips to delicately extricate older interior leaves.

High intensity grazing using high stocking rates for short durations are frequently recommended for controlling invasive brush infestations in western U.S. rangelands (Campbell and Taylor 2006). The high stocking treatments employed three times the number of goats as the low stocking treatment (Table 1), yet low stocking treatments took a little less than three times longer in the summer grazing, and just a little more than two times longer in the fall grazing compared to high stocking treatments, to deplete plot forage.  Large numbers of grazers in close confinement seems to produce greater psychological pressure to feed intensely and a sort of feeding frenzy ensues resulting in less selective feeding and a more complete consumption of target vegetation.  Even so, our low stocking treatments uniformly stripped the vegetation on their paddocks, albeit over a longer period of time.  Unlike the destructive continuous grazing described by Professor Den Uyl in part 1, goats were removed from their research paddocks once most forage was eaten, allowing the understory vegetation to regrow.

Visual impacts immediately following prescribed grazing treatments showed heavy to near complete defoliation of woody plants up to 6 – 7 ft. in height and severe reductions in herbaceous plant cover for most species. Additional reductions in woody cover and height occurred through debarking or breaking small stems by horn rubbing, particularly on spicebush stems.

One year following the initial grazing, multiflora rose leafed out vigorously and grew new canes.   However, modest reductions in rose were seen, ranging from an 8 to 10 percent reduction in cover and a 0.8 to 1.4 ft. average reduction in height.   However, no rose plants were killed following one year of grazing.  It’s too early to know how grazing will impact native species diversity.  After the first season of grazing there were no decreases in number of native plant species, woody or herbaceous.

As I mentioned earlier, goats are considered generalists in their feeding behavior. However, some selectivity occurs depending on palatability and the individual animal’s previous experience with different plants. In this study, almost all species within reach were ultimately fed upon. Notable exceptions included pawpaw and wild ginger, which aside from some stem breakage and trampling, were not fed upon at all.

Prescribed grazing alone may eventually eradicate non-native invasive infestations, like our multiflora rose, but only after three or more years of intense grazing pressure.  More research needs to be done to look at multiple years of grazing and its impact on both target invasive vegetation and non-target native vegetation.  In fact, this study is now going into its fourth year of grazing and will produce those results.  In some circumstances, forest managers may find multiple years of prescribed grazing too damaging to desirable non-target vegetation.  The good news here is that even where one short-term grazing is applied to dense brush, prescribed grazing with goats cleared between and pruned back large shrubs sufficiently to allow workers much easier access to much of the area that was largely inaccessible.  Prescribed grazing could be used in combination with conventional mechanical cutting and herbicide treatments to reduce costs and chemical inputs into the environment.  Where complete eradication of invasive vegetation is desired, prescribed grazing will most certainly need to be followed-up with herbicide treatment.

Much more work needs to be done before foresters and other natural resource managers can feel comfortable making management prescriptions using prescribed grazing.  An overriding factor determining the viability of prescribed grazing as a forest management tool, and one not addressed in this article, is cost.  Determining the economic feasibility is a complicated matter.  A wide range of prescribed grazing services models could be applied.  Landowners and managers could maintaining their own “forestry” goat herds, contract with a “herd for hire” enterprise dedicated solely to providing vegetation management services, or offer free forage to a neighboring goat farmer, with many other variations possible.

Having fought bush honeysuckle, multiflora rose, Japanese honeysuckle, autumn olive, and other invasive species across many forest acres over the past two decades using chainsaws and brush saws, tractor mounted sprayers and backpack sprayers, hydraulic rotary brush cutters and tree shears, and having sprayed thousands of gallons of glyphosate and triclopyr, 2,4-D and Arsenal, not to mention Tordon and Escort, I’m getting tired and ready to try a fresh approach.  Watching those adorable, furry ungulate friends of mine munching so eagerly on the arch enemies of my forest just does my heart good, refreshes my hope, and reinvigorates my desire to continue the fight.

Bringing this discussion full circle, I never imagined as a young forestry student steeped in the tradition that proclaimed the evils of fire and livestock in the forest, that I would be writing an article on the tremendous possibilities of both as forest management tools.   Prescribed fire is now being used as a tool to help promote the establishment of oak regeneration.  It sounds good, but for many private landowners it’s just not an option.  What about prescribed grazing as a sort of surrogate for fire in managing forest vegetation to favor oak regeneration?  Sounds a little crazy.  I think I’ll try it!  Come to think of it, I have already started.  That’s a story that will have to wait until next time.

Ron Rathfon is an Extension Forester with Purdue University’s Department of Forestry and Natural Resources since 1992. His primary focus is applied forestry research and forestry extension activities directed to private landowners, professional foresters and other natural resource professionals.

Literature Cited

Campbell, E.; Taylor; C.A. 2006. Chapter 9: Targeted grazing to manage weedy brush and trees. In: Launchbaugh, K. ; Walker, J., eds. Targeted Grazing Handbook. Centennial, CO: American Sheep Industry Association. 77-87.

Editor’s Note: Part 1 of this story was published in Volume 23(3).