Put 200 cow/calf pairs on a couple of acres of pasture. A few hours later the grass is eaten or heavily trampled. Not a pretty sight. Yet this ultra high stock density (UHSD) grazing approach, also known as mob grazing, is working for some cattle operations with stock densities as high as 500,000 lbs. per acre.
Speaking at the Feb. 24 Southwest Missouri Spring forage Conference in Springfield, Mo., Doug Peterson, a grasslands specialist with the Natural Resources Conservation Service, laid out the advantages and disadvantages of UHSD. Intended to model the grazing patterns of herd animals such as the buffalo, UHSD places a large number of animals in a small space, moving them frequently — perhaps as often as every 30 minutes — between plots. The worked-over forage rests for as much as 90 days before the process is repeated.
UHSD increases the length of the rest period, shortens the grazing period and greatly increases stock density. Stock density is defined as pounds of beef per acre. If you have 40 1,250-lb. cows grazing on 10 acres, that’s 50,000 lbs. on the hoof. Divide pounds by acres and you get stock density: 5,000 lbs. of live weight per acre. If you put those 40 cows on one acre, the stock density jumps to 50,000 lbs. Put them on a quarter acre, and the stock density is 200,000 lbs.
According to Doug, high stock density is generally 50,000 to 250,000 lbs. UHSD is 250,000 and up. This grazing approach can work for many livestock producers for a few months a year on selected pastures and with dry cows. UHSD is ideal for combining herds even between farms, where neighbors share the work load of moving the cattle from pasture to pasture.
The biggest mistake, said Doug, is grazing too intensively and creating a “scorched earth” situation. He recommends 60 percent utilization, which leaves trampled vegetation for a mulch effect and allows the forage to recover.
Among the benefits of UHSD are:
• Improved soil health – This type of grazing produces significant amounts of organic matter through root die-off and trampling that enriches the soil. The mulch created from trampling keeps the soil surface cool, improves infiltration of water and is a food source for microorganisms that start the natural mineral cycle that builds productive soil.
• Manure distribution – Studies have shown it would take 27 years to place a manure pile on every square yard of a pasture. On a two-day rotation, it would take two years, and with UHSD even less than that.
• Weed and brush control – Doug cited a southwest Missouri farmer who used UHSD grazing in a pasture with sumac, a plant cattle will normally not touch. Little of the sumac remained after the grazing period, which saved the farmer the time and expense of spraying or burning to remove the sumac.
• Wildlife habitat – The longer rest periods between grazing are attractive to certain kinds of wildlife. Hoof action also encourages more legumes.
• Livestock performance – If forage and livestock are managed properly, performance can be excellent, said Doug. You don’t want livestock to eat too much of the forage. He’s found UHSD also keeps the energy/protein ratio in balance in the spring and fall when cows can get too much protein.
