Ultra-high stock-density grazing – or what some people call mob grazing – restricts a large number of animals, especially cattle, to graze a small area usually for a very short period.
You may be asking, “How large a herd?” “How small an area?” There is no strict definition, but some folks have suggested that it be at least 300,000 lbs of animal per acre, says Bruce Anderson, University of Nebraska Extension forage specialist.
That’s around 200 cow-calf pairs per acre or 1,000 pairs on five acres or 50 pairs on a quarter acre. A few mob-grazing experts have gone more than three times higher, to over one million pounds of animal per acre, he says.
“Obviously, this mob of animals usually will finish grazing all the available forage in just a few hours. So it’s not unusual to move them to a fresh area to graze several times a day. Or even eight or more times per day if you’re pushing a million pounds per acre.”
Nearly everything in that small area is either eaten or trampled, including weeds and less-palatable grasses. More of the total biomass grown gets used as feed or is recycled back into the soil litter. Manure also gets distributed very evenly and also is trampled into the soil, improving soil fertility.
Anderson tried mob grazing for the first time last year and started again this year a few weeks ago. He found that the looks and the response of the pasture to mob grazing are quite different under wet conditions compared to under dry conditions.
“I haven’t advanced to the million pounds of animal per acre level yet, but I am pushing half a million pounds; I move the herd two to four times a day. I learned quickly that it’s easy to move the animals. Cows aren’t dumb. When they’re out of grass and they see someone coming, they know they are going to get some fresh pasture and they better come quick or the other cows will have it gone before they get there,” he says.
This year, like last year, it rained just a couple days after Anderson started mob grazing. “Quite frankly, I don’t like what I see under wet conditions. With ultra-high stock-density grazing on clay loam soils like I have, pasture quickly becomes a muddy mess. Mud gets on what once was good grass and animals refuse to eat it. After a couple hours, the whole area looks like a mud hole.”
His pasture is mostly bromegrass, bluegrass, orchardgrass, alfalfa, and clover. Last year he noted that badly muddied areas recovered much slower than nearby drier spots and that alfalfa was the fastest to recover. “We worry about damage to alfalfa when grazing on soft, wet soil but maybe damage was minimal because animals were there only a few hours. I also was surprised that brome seemed to be hurt the most. It took more than 90 days for brome to look ready to graze again last year, and this year I see that the brome stand is thinner in those same areas.
“I will watch again this year to see if the response is the same and report to you later in the summer,” Anderson says.
For more on mob grazing, see our Hay & Forage Grower article, “Extreme Grazeover.”