Mob grazing — heavy stocking on small paddocks of forage — intrigues livestock producers. Promised benefits of increased soil organic matter, even distribution of manure, and more diverse forage species are talking points of promoters.
Justin Sexten, a University of Missouri Extension nutritionist, wants to see more data. “I know of only one Midwestern research report regarding mob grazing and it does not support promised benefits. That concerns me,” he says.
Foremost, Sexten worries about nutrition. “I’m not a soil scientist. I’m not a plant scientist,” he says. “But this appears to be a way to limit feeding. It may apply to dry cows, but I wouldn’t use it for stocker calves to put on pounds of cheap gains.”
As a demonstration, Sexten put a half-million pounds of beef per acre at the MU Forage Systems Research Center, or FSRC, in Linneus. That was a small mob; some mob graziers use twice that rate.That half-size mob devastated the forages.
“We didn’t get answers, but we got lots of questions,” Sexten says after putting so many cattle on limited space. The cattle did trample the soil, as claimed by promoters.
However, instead of normal FSRC rotations with 30-day rest periods after management-intensive grazing, the mob-grazed paddocks took longer to regain forage cover. Weeds came back in place of grass and legumes.
Sexten figures cows got only 50% forage utilization. Managed grazing systems should increase, not reduce, use. Grass tromped or covered with manure and urine isn’t eaten.
Land costs are a major concern in all livestock grazing systems. Reduced use and long rest periods boost land rent for a herd.Nutrition comes into play, quickly.
Proponents of mob grazing say that cattle should be held off until forage matures, say to waist-high, to increase organic matter to be tromped into the ground.
Maturity increases nutrition risks, Sexten says. Overmature forage loses nutrient value. On pastures of infected tall fescue, the most common forage in Missouri, toxin content increases and concentrates in mature seed heads.
Seed stalks increase potential for pinkeye infection. Disease negates gains, and increases costs and labor.Mob grazing provides a specialized tool for limited use, Sexten says. It’s not a system for feeding a herd.
“Taking CRP [Conservation Reserve Program land] out of retirement, mob grazing could be useful,” Sexten says. Long-standing forages grown up in weeds and brambles need intense grazing pressure.
An early national report on mob grazing came from Texas. A ranch estate that had not grazed cows for years was overrun by mesquite and mature grasses. New ranch managers turned in a mob. With heavy stocking, what wasn’t eaten was stomped into the ground.
On that range, the soil seed bank provided a new stand of prairie grasses. Mob grazing rescued neglected land. At FSRC, weeds returned to trampled ground.
Mobs might control fall pastures that got out of hand over summer. Instead of strip-grazing, with no back fencing, the herd could be confined to trample the forage into the ground. But, tromped ground would be exposed over winter until spring regrowth. Freezing and thawing does help soil recover, Sexten says.
Cow management in mob grazing becomes critical. For most small herds, say 35 cows, the exposed paddock size is one-fifth of an acre to gain needed concentration. In tight grazing, social issues arise. Boss cows dominate the limited feed. Needy 2-year olds and old cows are shoved aside.
“I’m not sure how you’d manage breeding during mob grazing,” Sexten says. Anything over 35 cows would require two bulls. In large pastures, bulls can settle their fights over turf and cows. They can’t do that in a confined space, however. The bulls would spend their time fighting what they see as an intruder, instead of doing business.
Back to nutrition: To achieve pounds of dry-matter-intake per cow requires more management, Sexten says. Instead of moving cows every two or three days, they must move two or three times a day. That involves moving waterers with the mob. That’s more critical in warm weather, especially if cows don’t have shade. Trees are unlikely on small paddocks.
“There are so many questions raised about mob grazing,” Sexten says. “You have to think about how to manage the mob. A two-year study just released by Iowa State University showed no gain in soil organic matter from mob grazing. Building soil organic matter takes time, and is not something done quickly. Undoubtedly, it depends a lot on underlying soil types.”
For now, Sexten sees more questions than answers on costs and benefits of mob grazing. It’s not something to bet the farm on; the cost of feed might shoot up at the same time the grazier needs to buy it.Mob grazing is something to think long and hard about before adopting.
This article published in the May, 2012 editionof MISSOURI RURALIST.