When done properly, having a very high number of animals graze a small plot of forage intensively for a short time can result in more overall yield along with possible control of such pesky weeds as the Canada thistle.
That grazing concept, which is referred to as "mob grazing," has been intensely studied during the past three years by University of Wisconsin-Madison graduate student Anders Gurda, who is an agroecology major with a special interest — for his thesis — on whether Canada thistles can be controlled by grazing practices in pastures.
Gurda shared his understanding of and findings on the "mob grazing" concept at a "Pasture Talk" program sponsored by the Glacierland Resource Conservation and Development Council. His overall assessment is the practice is "more than a fad but not an all or nothing or a silver bullet."
Through direct or survey contact with nearly 200 practitioners of "mob grazing" in Wisconsin, Iowa, Minnesota and Illinois, Gurda noticed there is no general agreement on its definition, despite how often it is talked or written about, or on how it should be fitted in a grazing and forage production plan in the Upper Midwest.
One point that needs clarification is that mob grazing, which is a measure of stocking density, is not the same as stocking rates, Gurda emphasized. Stocking rate numbers pertain to the number of acres needed per animal for a full grazing season while mob grazing refers to a high number of animals placed in a parcel of land for a few hours up to about one day, he explained.
On the ground, mob grazing requires the doubling or more of the number of parcels or grazing paddocks — not necessarily an overall increase in acreage — that would otherwise be lined up for the less intense rotational grazing approach, Gurda said. In many cases, it could require the animals be moved to a new spot several times a day.
The natural history of much of the landscape in the Upper Midwest, particularly in areas to the southwest of Wisconsin, shows the region is suitable for grazing, Gurda said. Citing how the bison found the habitat to be ideal for the huge roaming herds centuries ago, he suggested that today's managed grazing strategies can mimic the era of the bison.
Gurda also cautioned, however, that "mob grazing" is possibly being oversold by a number of gurus who have emerged. There are no guarantees because not enough evidence has been obtained to advise the widespread adoption of the practice.
Mob grazing typically means that a longer rest period of 60 to as many as 90 days is appropriate before animals are brought back onto the same patch of forage, he said. With traditional rotational grazing, that rest period is usually 30 to 40 days.
Where mob grazing has been practiced and compared to other grazing routines and timelines, there has been better productivity, more even use of forage, less pickiness by the animals, a more even distribution of urine and feces and improvements in soil health, Gurda said.
In addition, both the trampling of some forage and the longer rest periods are likely to contribute to an increase in organic matter in the soil.
With a combination of cool and water season grasses in the grazing paddocks, improvements in species resiliency has been observed and openings are created for desirable species that would otherwise be suppressed, he added. Cycles of disease of animal pests can also be broken with a differing timetable on grazing rotations.
By allowing longer rest and recovery periods for forages, the grazing season can probably be extended, resulting in more profitability because of savings on hay harvesting, handling and storage. Gurda also mentioned a better diversity of bird populations and a better opportunity on successful nesting for the birds.
But there are also drawbacks with mob grazing, Gurda pointed out. An obvious one is that the longer rest period means more mature and lower quality forage that is most suitable for beef cattle, dairy heifers and dry cows, but not for cows during a milking lactation.
More time and labor will be required in order to move the grazing animals quite frequently, he added. Wet environments or a period during or immediately after a heavy rain will result in more trampling and waste of forage than desired and probably in pugging and soil compaction.
Regarding weed control, Gurda said it takes three or more years to start reducing the population of Canada thistles through grazing practices, of which mob grazing has the best potential. He explained the thistles can spread both by seed production and by their horizontal roots — processes that can be disrupted by grazing of all vegetation; by smothering and trampling that tend to accompany mob grazing; and by being eaten by animals when the thistles are at their vegetative weakest point (during budding and flowering).
Responding to a question, Gurda indicated that paddocks with newly-established forages and those which were frost-seeded in the spring are not good candidates for mob grazing because of the amount of physical disturbance to the plants and soil. Clovers are not a good species for mob grazing, but most grasses, especially Reed canarygrass, tend to fare quite well with the practice.
To answer the question about what grazing method provides the most forage during a growing season, Gurda has monitored research plots at Lancaster, Hollandale and Prairie du Sac. Among the forages grown were tall fescue, Kentucky bluegrass and quackgrass, along with weeds such as thistles.
Even during the severe drought at those locations in 2012 and a shortage of moisture during part of the 2013 growing season, higher yields of forage and more consumption of it were achieved with a mob grazing approach, Gurda reported. He suggested one reason was the trampling of some of the forage, which resulted in a soil cover that reduced how much effect sunlight had in drying out the soil. It was also noted that thistles are not drought tolerant, he added.
It's not bad as such to have certain weeds as part of plant diversity in pastures, Gurda observed. He mentioned the early growth stage of dandelions as a palatable forage and indicated that Canada thistles can be a somewhat better feed than alfalfa in a pasture.
What's not acceptable in any method of grazing is to expect animals other than goats to eat woody plants that dairy cattle typically refuse and to try to get any animals to eat plant species which are toxic to them, he said. Trying to control weeds with herbicides can be effective, but it will come at the cost of wiping out clovers in the pasture and will result in the lowest overall forage yields.
Gurda reviewed the results of a survey of mob grazing for which about two-thirds of the respondents were from Wisconsin. Among the 187 respondents, 83 percent were grazing cattle (25 percent of them dairy), while another 14 percent had sheep.
Their opinions of mob grazing were not as positive overall as what has been portrayed by the gurus advocating the practice, Gurda said. When asked for their sources of information about mob grazing, the survey respondents listed other farmers and presentations at conferences as the top two.
Among the diverse group of respondents, including those engaged in grazing as a full-time or part-time enterprise, the reasons in favor of mob grazing were lower spending on nutrients, less plant selectivity by animals while grazing, better weed control, more organic matter in the soil, better moisture retention in the soil, enhanced forage resilience, more plant diversity and production and the ability to graze a few more animals, he said.
Drawbacks echoed those which Gurda had mentioned: more labor and time requirements; extra fencing; lower forage quality; more dependence on the environment; the risk of pugging and soil compaction; suitability for only certain kinds of animals; and lack of experience.
Of the survey respondents, 70 percent were employing mob grazing more than one-half of the time during the growing season. They had herd sizes of 26 to 200 animals, rotated one to three times per day, chose to leave four to seven inches of forage residual and allowed rest periods of 31 to 60 days before the next mob-grazing round.
Because the results of mob grazing can be quite good or very bad, Gurda urged no more than a piece-meal rate of adoption. It depends on the season, the environment and the animals.
Look at mob grazing as no more than a strategic tool at the moment, he said. According to Gurda, more research is needed on the claims being made on its behalf.