Call him a skeptic, but Glenn Shewmaker thinks mob grazing shouldn’t be a standard practice, is best used for special conditions and, in some cases, can cause more harm than good to animals, pasture and soil.

The University of Idaho Extension forage specialist has been informally studying the effects of mob grazing after talking with graziers and colleagues about this latest grazing “fad.” He’s concerned that some may consider mob grazing “the next step” after rotational grazing; he thinks it’s “on the edge.”

To be successful, graziers who stock a high density of cattle on pasture for a short time need to manage that practice intensively and consistently, Shewmaker says. The time and energy requirement is “about like milking cows.”

Mob grazing is not a panacea, he says. “It’s definitely not for every producer. We have trouble enough just getting some people to rotate. To reach those ultra-high densities, you have to move animals several times a day. My guess is that the majority of people aren’t going to commit to that intensive of a management situation.”

Mob grazing has been touted as a way to improve soil health. The effects of high animal stocking rates are better nutrient distribution and more uniform utilization.

“Our research shows that pastures are very good at sequestering carbon and that’s certainly a good thing.” But mob grazing provides more hoof action, increases nutrient cycling and speeds up oxidation of organic matter, Shewmaker says. “When you’re doing that, you’re losing carbon, similar to tillage operations.

“I think the claims of benefits to soil health are exaggerated. All we’ve heard is antidotal information, and I would really like to see data on soil bulk density and water infiltration rates.”

Short term, mob grazing causes soil property problems, he says. “Mob grazing increases soil bulk density, so there is more mass per unit volume. When you do that, you have less pore space and can have less oxygen if it gets saturated with water. More importantly, it’s much harder for water to infiltrate the soil, so then you’ve got runoff, whether it’s from rain or from irrigation.”

Letting pasture plants mature during rests may give the soil more time to develop a good structure between grazing cycles, he admits. “But too much hoof action will break down soil structure, at least on the surface if it’s dry, and if it’s wet, it’s going to cause compaction.”

Mob grazing works well for someone trying to reclaim land or in areas with large weed infestations where herbicides can’t or won’t be used. “There are situations where mob grazing has a purpose,” Shewmaker says.

But graziers considering mob grazing need to know how much commitment it requires, he adds.

“If something happens and you get there an hour late (to move cattle), you’ve affected animal production. There are only so many hours a day animals can eat and ruminate and rest. So if you’re an hour late, you’ve stressed animals and possibly the plants. They can compensate a little bit in the next cycle, but they’re never going to gain that (production) back.”

Animals behave differently in a mob grazing situation, too, he says. “When you confine them too close, you’re going to get some pushback. You reach a point where there’s going to be more social interaction that’s going to decrease performance than if you give them a little more room. There’s a bit of a feeding frenzy. That’s partly the method to mob grazing, but there are negative consequences as well.”

He advises interested graziers to research the practice carefully and decide how much time and energy they can commit to it.

For another view on mob grazing, see our November 2009 story, “Extreme Grazeover.”

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