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All things pertaining to pasture, rangeland and grazing management, forage plant species, and feeding ruminants. Discussions range from tame hayland to native rangelands.  

Overgrazing is All in the TIMING

Feb 15, 2019

In my adventures on the social media interface, I often come in contact with people who have used different terms to deliberately undermine the value of livestock on the landscape. One of those terms is “overgrazing.”

Far too commonly the term “overgrazing” has been so over-used and abused that its true meaning has been virtually lost. It’s often used to justify the demonizing of livestock for all of the world’s environmental problems, from desertification to climate change.

Overgrazing is a term that is highly misunderstood and misinterpreted, even by the world’s most famous dictionaries. It’s usually defined as “having too many animals on the landscape.” This is no matter if it’s on tame pasture, on native prairie, silvopasture, savannah or forest meadows. Overgrazing is also referred to as “land grazed too heavily,” where the vegetation is so damaged and made scarce that the land becomes “liable to erosion.”

So, what IS overgrazing??

Overgrazing is a function of TIME, not the number of animals.

It doesn’t matter how many animals nor how many acres you have to graze. Overgrazing can occur with just a few animals on a lot of land or a lot of animals on a small amount of land. It is always a result of mistakes made in management, intentional or not.

The real definition is this: “To defoliate a plant before its energy stores have been fully restored.” That plant is trying to regrow after being defoliated (grazed, cut, or mowed). In other words, overgrazing is when a forage plant is bitten more than once during its growth period, or when it is trying to regrow and must use its energy reserves in order to do so. This second bite pushes the plant further back to the point where its recovery period will be significantly longer, and it requires more energy than before to regrow. If the plant is not given sufficient time to recover, it will become more stunted both above and below-ground, or it will die.

This is all a matter of timing.

Plants require time to regrow after being defoliated. Defoliation is done by either by grazing, mowing, or even burning.

Just think of a lawn. A lawn is covered in living green plant matter called “grass” that regrows after mowing.

Here’s the mind-blowing part: It takes time for that cut lawn to grow back before needing to be mowed again!

Let’s go back to the pasture because I find mowing lawns a rather unfair comparison. The pasture is largely composed of grasses, often with at least four different species. There may be some legumes in the stand. But let’s focus on grasses for now.

I already mentioned that it takes time for grass to grow. Grass has a growth curve that is in the form of a face-down S curve (forage yield is the exact opposite), and this growth curve is broken up into three phases.

  1. Phase 1 (“baby” phase): Grasses begin growth (some have begun growth the previous fall, then stalled because of freezing temperatures) from tillers or seeds. After grasses are cut for hay or silage, this growth will also occur. The new plants coming up are actually from “tillers” at the base of the parent plant, or from spreading rhizomes. Grasses are most sensitive to defoliation/grazing because their energy reserves are being used for growth. Once they have put even one leaf up, they are starting to generate photosynthesis to supply more energy to the plant. But not all energy; right up to the start of Phase 2 plants are still relying on energy stores to continue growth and will drain those stores right up until there is enough leaf area to convert sunlight energy into energy storage in the base of the plant and main roots.
  2. Phase 2 (“teenager” phase): Grasses experience the fastest rate of growth at this stage. Photosynthesis is being maximized because most of its leaves are out and collecting sunlight, and the plant is filling up its depleted energy stores from Phase 1 in preparation for Phase 3. Grazing early at this stage can be dangerous if animals are not controlled so that they move quickly after lightly grazing plants at this stage. There is a little more lee-way when grasses are later into phase 2, because their energy stores should be filled up enough to start pushing up a seed-head. 
  3. Phase 3 (“oldie” phase): Grasses produce a seed head and begin flower production, which eventually moves into seed production, which leads to senescence or death of the parent plant. With the right growing conditions, the tillers at the base of this plant will begin to grow.

When grazing animals, we should not strive to have animals eat plants when they have the greatest quality in energy (sugars) and protein, but rather that optimal point when quality is decreasing as quickly as yield and fibre content. 

Overgrazing occurs at three primary timing points (some call it the Three Cardinal Sins of Grazing, as from the grazing schools of Jim Gerrish):

  • Staying too long
  • Returning too soon
  • Taking too much

Again, all three of these can and will occur no matter the size of the pasture or the size of the herd.  Animals that are allowed to stay too long in the pasture will take too much: They will take the “second bite” of grass that they grazed a day or two ago. 

Often the reason for returning for that second bite is because they are allowed to select what plants they want to eat. Selectivity by all livestock is primarily based on taste and smell, and somewhat past teachings and experience by Momma Cow or the School of Hard Knocks. If a plant tastes good the first time, chances are that the animal will return to that plant once it has been able to taste most of the rest of the plants in that pasture. 

I’ve turned out our steers onto a 50-acre piece of pasture–only 60 animals–and what they do when they smell a tasty plant is to take a bite, then move on. They move on because of their strong herd instinct, and because they feel they need to peruse the pasture to taste and smell what’s out there. Until they’ve gone over most of the pasture, will they come back to eat those plants they found quite tasty again.

This is what I’ve found in raising cattle the conventional way of selective, set-stock, continuous grazing. 


In coming back again for that second bite, those animals are returning too soon. The bite they take can remove about half or more the leaf area of a plant (sometimes an entire plant)–if you don’t believe me, find a decent stand of grass (again, not lawn) and pull up, with your hand, 10 grabs of grass. See how much is left in that spot you’ve picked from. One hand grab of grass is typically the same amount of grass and the similar force required by the cow to graze.

So when cattle or any grazing animal is allowed to come back too soon for whatever reason, that means that plant isn’t allowed enough rest to recover. Leaf area is needed for a plant to generate photosynthesis to replenish energy stores and generate energy to regrow. Not enough leaf area could mean that plant needs to rely on its energy stores for regrowth. 

And when the plant is grazed when those energy stores are already depleted, means that the plant is either going to be growing much, much slower through the season, or it will die. 

Do you see how the concept of time in regards to the subject of overgrazing is applied? Here it is in regards to the phases discussed above:

One bite to a grass plant that is in late Phase 2 pushes it back to either early Phase 2 or late to mid-Phase 1. Two bites push that same plant back to early Phase 1. 

This is a result of staying too long, coming back too soon, and taking too much. 

How do you mitigate overgrazing then?

Control animals using temporary and permanent electric fence. Divide a big pasture into many smaller paddocks, and move the animals quickly enough that they are not going to selectively graze and take that second bite. 

Doing so ensures plants get adequate rest, and there is plenty of residues left behind until the next grazing period.

The amount of rest a pasture needs depends on the stage of growth and time of year. Plants growing quickly will require you to graze quickly. Slow growing plants means you graze slower. Tighten up your paddocks when grasses are growing quickly, and make them bigger when plants are growing slower. 

Rest can be anywhere from 3 weeks to 18 months. Native grassland requires longer rest periods than tame forage stands. Fast-growing tame grass stands can be returned fairly frequently, unlike most native grass stands. 

And do not be afraid to “waste grass.” Wasting grass is a good thing because it covers the soil surface and slows the raindrops from impacting the soil surface. It also gives the soil flora something to eat and convert into organic material, topsoil, and sequesters carbon. 

Good grazing practices that involve more management and less selective grazing also means mitigating soil erosion and desertification. 

It all sounds counter-intuitive, but when you put the puzzle pieces together, it should all make sense.


A Few Exceptions: Dormant-Season/Stockpile Grazing

Much of what I talked about above was in direct reference to the green, and often growing plants of the pasture. Overgrazing during the point in time when these plants are growing and putting down energy root reserves as they do so is certainly something that must be taken into account in grazing management.

But there are some exceptions to the rule as mentioned above. These exceptions go right into the aspects concerning dormant-season grazing. 

The basic concept is that, for dormant season grazing (or what others [myself] call stockpile grazing), you are putting animals on a pasture stand that has received an extended amount of rest during the growing season, and with plants that have accumulated more than enough energy root stores to withstand some heavy grazing treatment and that may get cows to take more than just one bite per plant; not to mention, with the desired herd effect (mobbing), a good bit of trampling as well. 

During the dormant season, plants can take a whole lot more “abuse” than if those same plants were grazed while they were still recovering energy reserves from spring growth, or as I hoped to communicate above, after the first defoliation event. Of course, that doesn’t necessarily mean that you can push those to eat the grass plants right down to the nubs during the dormant season, as you still need some residue left behind to protect the soil, especially on a regular basis! No, that wouldn’t be good at all. But, this kind of “abuse” (for lack of better terms) certainly opens up the canopy, gets rid of a lot of dead plant material from previous years and turns it into meat, milk, and fertilizer (manure), and encourages vigorous plant regrowth and biodiversity when that area is allowed sufficient recovery time. 

See, the whole concept of overgrazing, as I was harping on about above, is about TIME. Recovery time in particular. 

It certainly would be considered overgrazing if a particular part of the pasture was dormant-season grazed, then the animals were turned back onto it when the plants’ energy root reserves were low. That in itself is strongly discouraged and considered poor management. 

I also understand that I focused on grasses only and not on other species, nor biodiversity, nor soil health. 

The thing is, the basic concepts are the same: Time to rest so that a plant stand has time to recover sufficiently is a crucial part of grazing management. 

That time is going to depend on what’s in the pasture, other than just grass. Time will need to be allocated to accommodate for legumes in the stand, like alfalfa, trefoil, clovers, and even sainfoin. Legumes and other sensitive forbs can be easily chased out of a pasture if you’re only managing for the grasses; Or, on the other hand, other species that are more sensitive to heavier grazing will start to move in. You need a balance of both with timing. 

Manage for the soil as well; that should be priority. The principles are the same: Cover the soil, living roots in the soil at all times, manage for biodiversity by trying to be more biodiverse with your grazing “tools” (rather than just cows, use sheep, chickens, goats, etc.). 

Manage for the whole system, or rather on a holistic context. Your land that you are the temporary steward of now, will thank you.