Benefits of Selective Grazing

Most graziers and even a large number of would-be graziers these days have heard about the downside of selective grazing.

Selective grazing, in a nutshell, is the natural instinct of livestock to eat the plants that taste best to them at the moment and leave the rest. (The alternative is to stock paddocks densely enough that the animals graze each paddock down evenly like a mower.)

The problem with selective grazing is that, when livestock persist in eating only their favorites, eventually their favorites die out. The result is a pasture largely populated by “weeds.”

While this is clearly an undesirable outcome, there can actually be a positive side to selective grazing—under the right circumstances.

Animal Benefits

Consider the reasons an animal might graze selectively in the first place. For one thing, many toxic or harmful plants are bitter, prickly, or otherwise undesirable. Livestock often avoid these harmful plants when given the choice. Forcing them to clean up a paddock may cause them to ingest something they really shouldn’t be eating.

For another thing, animals actively seek out plants that meet their needs. Rapidly growing cattle tend to seek out nutrient-rich “ice cream” grass for a reason—because it will provide them with the energy they need to keep growing.

But this instinct does not prompt livestock to only eat the “ice cream” forages. An obvious and familiar example is the preference of goats for trees and other such browse. The types of plants goats prefer are higher in minerals than grasses are; when goats are forced to eat primarily grass, they eventually begin to suffer from nutritional deficiencies. But this behavior does not extend only to goats—mature cows have been observed supplementing their diets with forbs (soft-stemmed broadleaf plants) commonly dismissed as “weeds” when an adjustment in mineral intake is required for health.

The Pasture Problem

While there is a case to be made for the benefits of selective grazing as far as the animal is concerned, this still leaves us with the problem of the effect of selective grazing on pastures. Over time, allowing animals to continue to eat the same plant species over and over again will eventually cause those species to die out. The pasture will not only be taken over by less desirable species, but it will become very uniform.

Note that selective grazing is not the only means by which a pasture becomes uniform. Mowing a hay field to the same height at the same time of year every year will also create a uniform forage stand. Ironically, intensive grazing strategies such as mob grazing also produce uniformity—the grazier simply manages his rotation to favor a uniform stand of desired grass species versus “weeds.”

The problem with uniformity in a pasture is that uniformity is antithetical to resilience. We see this starkly illustrated in large grain fields. If drought hits, the whole crop from that field may be lost. If disease strikes, it will spread rapidly from plant to plant. If an insect pest finds food to its liking, it will bring an army of relatives, since there will very likely be little in the way of predators to stop them. In fields where these problems do not cause complete devastation, it is usually due to pesticides, irrigation, and other such interventions.

Contrast this to the multispecies abundance of a healthy prairie, or any other ecosystem for that matter. Such an environment is home to a complex interaction of numerous plants, which in turn host a diverse array of insects and other animals. The result is a well-adjusted system of checks and balances—in a word, resilience.

The Solution

Then the question becomes how to avoid uniformity in the pasture. Furthermore, can it be done in a way that respects or even takes advantage of the natural selectivity of grazing animals?

Yes, if the grazier is willing to take an adaptive approach to grazing management.

Take a look at what produces the abundance of the healthy prairie in the first place. The one thing that produces such resilience is not grazing, nor is it annual fire. It is variety. Specifically, it is variety in the form of irregular bursts of intense disruption of varying types followed by rests of varying duration.

In this prairie, a flood one year may favor a certain number of species, but it will be offset later by a drought that favors others. Fires will set back all plant species they touch, making room for others to germinate; but these fires will occur, not on a schedule, but when there is sufficient combustible material to burn, favoring different plants in different years depending on the season of the fire. Different animals will nibble on different plants at different times—not only the iconic bison but browsing animals such as deer and less visible herbivores such as grasshoppers.

Adaptive grazing management seeks to mimic this natural pattern. Different parts of the pasture will be grazed differently from year to year, with some parts grazed intensely, others lightly, and still others not at all. Furthermore, this grazing is not restricted to a set rotation of permanent paddocks used in a specific order, but moved in fluid fashion across the pasture using either temporary fencing or a strategy such as patch-burn grazing, which relies on fire to attract livestock to a given part of the pasture much as Native Americans burned prairies to attract bison. The grazing pattern is adjusted from year to year and even perhaps from season to season as conditions change.

Pasture Benefits

As the goal is no longer to knock down all the forage in a given series of paddocks, more selective grazing can be allowed, giving animals the nutritional benefit of their favorite forages. Furthermore, this benefit can be conferred without sacrificing the resilience and abundance of the pasture.

Better still, the selective grazing preferences of different animals can be matched to the needs of the pasture. Permitting animals to follow their natural instincts in this manner allows for variability across the pasture not available with blanket treatments such as mowing or even a routine burning schedule.

For example, cattle eat mostly grass and relatively few forbs. Therefore, in spring, they can be put into a pasture overrun with a nonnative cool-season grass, such as smooth brome. The cattle will thrive on it, and repeated spring grazing over a period of several years will significantly reduce the dominance of the cool-season grass, allowing a more varied mix of plant species to grow.

Another benefit of careful selective grazing is that it will foster what some ecologists have called vertical heterogeneity, basically meaning that the plants are growing at different heights rather than uniformly. This concept is very similar to what we see in a forest, with grass and wildflowers growing under shorter trees and shrubs under a canopy of tall trees; it is also the principle that permaculture seeks to imitate through the creation of complementary plant “guilds.” This type of complementarity can provide habitat for wildlife, particularly insects and birds, as many species need different types of vegetation structure to carry out their various activities. For example, birds and rodents alike will often nest and hide in taller vegetation but feed in shorter vegetation.

So while selective grazing often gets a bad rap in grazing discussions, it is important to remember that it is only a tool. Like any other tool, it can be used thoughtfully in ways that are beneficial to both livestock and pastures, or it can be permitted thoughtlessly in ways that are destructive to both.

Sources

Helzer, Chris. The Ecology and Management of Prairies in the Central United States. Iowa City: University of Iowa Press, 2010.

———. “A Skeptical Look at Mob Grazing.” The Prairie Ecologist. November 28, 2011. https://prairieecologist.com/2011/11/28/a-skeptical-look-at-mob-grazing/.

Holmes, Cody. Ranching Full-Time on 3 Hours a Day: Real-World Validation of Holistic Systems for Stockmen. Austin: Acres U.S.A., Inc., 2011.

Salatin, Joel. “Impact: High or Low.” Meadow Talk. The Stockman Grass Farmer. September 2021.

Helpful Resources

Grazing Management by Species
More about the natural grazing instincts of each livestock species and how to work those behaviors into a grazing system.