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When mob grazing is not mob grazing

Bruce Anderson Published on 17 June 2015

Mob grazing is popular. If you aren’t mob grazing yourself, you know someone who is mob grazing. Or are they?

What is mob grazing? The book Terminology for Grazing Lands and Grazing Animals defines mob grazing, “In the management of a grazing unit, grazing by a relatively large number of animals at a high stocking density for a short time period.” While this definition looks okay, I think it lacks the specifics needed to adequately define mob grazing.

For example, 50 animals might be relatively large to a farmer who uses a half-dozen cows to keep weeds down on some non-tillable acres, while 1,000 cows might be just a nice group to a rancher with over 10,000 head grazing extensive rangeland. Likewise, one week is a short time period to someone who moves animals to new pasture at most a couple times a year. The grazier who commonly moves animals once or twice a day on irrigated pasture may not consider it short until the time period is only a couple hours.

And what is a high stocking density? One hundred sheep or goats per acre? Two hundred cow-calf pairs? Or 400,000 pounds of yearling steers? And is it determined by animal count or animal weight?

Many early adopters and proponents of mob grazing consider "mob grazing" to be a popular name for ultra-high stock density grazing. What is meant by “ultra-high” also is debatable, but many folks consider at least 200,000 to 300,000 pounds of animals per acre as the minimum to qualify for this category.

Two hundred thousand pounds (equal to 125 cows weighing 1,250 pounds with calves weighing 350 pounds) of animals will eat at least 2 to 2.5 tons of forage dry matter each day. This doesn’t even count the amount that will be trampled, fouled or otherwise left uneaten. One million pounds of animals, as has been reported by some graziers, will consume 10 to 12.5 tons of forage per day. With stock densities this high, these animals obviously can stay on one piece of ground for only a brief time. As a result, graziers who use ultra-high stock densities often move animals to fresh pasture several times each day.

Maybe the main question is “How does mob grazing differ from other grazing strategies like strip grazing, rotational grazing or management-intensive grazing?” After all, each of these strategies could include “a relatively large number of animals at a high stocking density for a short time period.”

Stock density can be increased quite easily simply by constructing smaller paddocks. This would be expected to increase forage utilization while reducing selective grazing and promoting more even grazing. Carrying capacity of the pasture can increase when this is successfully accomplished.

Likewise, the length of time animals graze a certain area can be shortened to whatever is desired as long as there is another area they can be moved to. Short grazing periods reduce the risk of animals grazing the regrowth of plants prematurely.

One objective commonly sought with mob grazing that isn’t part of most other grazing strategies is animal impact and herd effect. While mob grazing might be practiced successfully when forage availability is low, most often it is used when yield is high, like when grass is heading. Animals placed into pastures in this condition can obtain good quality forage briefly via selective grazing, thus maintaining desirable animal performance. Most of the forage available from this more mature plant material will be lower quality, however. If animals need much more than a maintenance diet, they must be moved several times each day to fresh pasture.

During this brief, selective grazing time period, much of the remaining ungrazed forage may be knocked down, but the occupation time will be too short for much actual trampling. To accomplish objectives such as true trampling and incorporation of remaining forage into the soil to hasten nutrient cycling, increase organic matter, improve soil health and other ecological benefits claimed by some mob grazing advocates, enough animals need to remain in the pasture for a longer time period. This will reduce animal performance at least for the time period this trampling is practiced.

The actual number of animals in the herd directly affects the outcome of this trampling. The animal impact and herd effect will be much greater where 200 cows are on 1 acre compared with 20 cows on one-tenth of an acre, although both have the same stock density. Similarly, mob grazing when soils are wet will result in a much different animal impact than grazing on dry soils.

The term “mob grazing” sounds interesting, so much so that it provides a sense of satisfaction to say you are using this novel, new grazing strategy. In my personal opinion, though, if mob grazing is more specifically defined as “grazing by a relatively large number of animals (100-plus) at a high stocking density (200,000 pounds per acre) for a short time period (move at least twice each day)” and part of the outcome is to truly trample and incorporate remaining forage into the soil, then unless all these conditions are met or exceeded, maybe it isn’t mob grazing. (Minimum thresholds in parentheses are my suggestions only.)

This does not mean that the extra paddocks or higher stock densities or the more rapid moves used in a strip grazing, rotational grazing, management-intensive grazing or other grazing strategy are not beneficial and evidence of improved management. It is just misleading to call it mob grazing.  FG

Bruce Anderson is an extension forage specialist with the University of Nebraska – Lincoln. Email Bruce Anderson.