Field Trial Looks at Mob Grazing for Dairy Herds

6/7/2014 7:00 AM

Many dairy operations incorporate grazing in some form from spring through fall.

As with any feed management practice, success relies on making sure there is adequate pasture quality and quantity available, a clean and accessible water source, and proper supplementation when needed.

A relatively new approach being evaluated on dairy operations is ultra-high stocking density, or UHSD.

This approach was originally developed using beef cattle in arid rangeland environments, and there is little science about this grazing approach on dairy farms in the Northeast.

With funding provided by a Northeast SARE grant, Aimee Hafla and Kathy Soder from the USDA Agricultural Research Service’s Pasture Systems & Watershed Management Research Unit, and Mena Hautau from Penn State Extension conducted a field trial to evaluate UHSD on dairy operations.

Ultra-high stocking density, or mob grazing as it is sometimes referred to, is characterized by high animal bodyweights per area — 500,000 plus pounds per acre for beef operations — small paddock size, mature forage, short grazing durations and long forage recovery times — 25 to 150 days.

Some of the perceived benefits include improved profitability from increased carrying capacity; improved animal performance; greater diversity of forage species; and improved soil organic matter, microbial action and water-holding capacity.

However, much of the research has been with beef cattle and to come to these same conclusions for dairy operations in the Northeast would require monitoring an operation over several years.

For the grant, the researchers from Penn State and USDA-ARS worked with four dairy operations that described themselves as UHSD and had been grazing for more than 15 years.

The participating farms were surveyed to determine their experience and management practices. Beginning in June 2012, one pasture on each farm was identified for mob grazing. Data were collected from June through November 2012 and April through June of 2013.

During the farm visits, information was collected about the number of cows grazing, pre- and post-grazed forage height, and pre-grazed canopy stratification. Samples also were collected for forage nutrient analyses.

In May 2013, soil samples were collected from each pasture in the study.

Results from the study showed that the stocking density on the dairy operations was lower compared with beef cattle. The range was 44,091 to 337,161 pounds per acre.

The pastures were rested longer — 30 to 49 days — compared with rotationally grazed herds — 21 days. The farms grazed the pasture at a higher height of 8 to 17 inches compared with what is typically grazed — 6 to 8 inches.

Most of the forage consumption was from the upper canopy, and the forage quality was variable throughout the season. Crude protein ranged from 14.2 to 32.2 percent, and neutral detergent fiber ranged from 33.6 to 60 percent on a dry matter basis across farms.

Soil parameters for the UHSD pastures were within recommended levels for the Northeast.

The implications from this study indicate that these four farms had taken a modified approach to the current UHSD grazing definition.

Forages were being grazed at a slightly higher maturity level by slowing the rotation to allow plants to mature. This strategy may increase the amount of forage dry matter available, but the lower quality forage may reduce milk production.

One key point that the researchers took away from this project is that there needs to be more research-based information for dairy producers.

Also, during a grazing field day, participants were asked to define UHSD. The responses were quite variable, and there does not appear to be a uniform definition and interpretation of what it means, especially at the field level.

The four farms participating in this project were well-managed and had many years of experience. They made a gradual shift to a UHSD system rather than an abrupt change.

More practical information is needed to determine the effects of this system on animal performance, profitability and soil characteristics.

More information on this project can be found at http://grazingguide.net/wp-content/uploads/2014/03/UHSD-Factsheet-Final.pdf.

Virginia “Ginny” Ishler is a nutrient management specialist and manager of Penn State University’s dairy complex.


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10/31/2014 | Last Updated: 3:45 PM