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Plan your forage supply for summer grazing

Brad Heins, assistant professor

April 11, 2015

Pasture is the primary source of forage for organic dairies, and organic livestock production regulations require a minimum of 120 days grazing per animal. In the northern U.S., this requirement is typically met by a May to October grazing season, and profitability depends on pastures that provide a season-long supply of high quality forage.

Spring and summer are just around the corner. This is a good time to start thinking about your pasture forage supply for grazing this summer. First, we will briefly provide results from a study where we evaluated pasture forage quality on Minnesota dairy farms, and then, we will discuss selecting pasture species when renovating a pasture. We monitored nine grazing dairy farms in Minnesota to measure monthly changes in forage quality of pastures over a two-year period. Farms were from a wide geographical area across Minnesota representing a range in herd size, pasture size, and pasture management. Across the nine farms, spring pasture dry matter (23.96%) was higher than summer (23.52%) and fall (19.76%) pasture dry matter. Seasonal average crude protein concentrations were 21.01%, 20.11% and 23.93% for spring, summer, and fall, respectively. NDF concentration in the pasture forage was different for spring, summer, and fall grazing. Seasonal NDF concentrations were 46.63%, 49.25%, and 45.97% for spring, summer, and fall, respectively.

Compared to monocultures, diversity reduces risks associated with loss of any single pasture species, provides for variable resource use within a field, supplies potentially more uniform biomass during the growing season, and improves soil health. Pasture diversity can be increased by adding grasses and forbs and by increasing numbers of species within grasses and forbs. An example is to grow nitrogen-fixing legumes with grasses. Although legumes supply nitrogen to grasses and provide a higher energy feedstuff than grasses, legumes are generally less persistent and require higher levels of soil fertility than grasses. Increases in diversity in a farm’s forage base can be achieved by planting mixtures in individual pastures, and by planting separate pastures with different species.

There are a lot of disagreements regarding the ideal number of species to include in pasture mixtures. Most agronomic guidelines recommend the use of a small number of species in grazed mixtures. Past research in the Northeast United States found that six to nine grass species were more productive than a white clover-orchardgrass mixture.

When selecting pasture grass species, producers should consider yield potential, palatability, and survival of grasses. Producers need to select species that are winter hardy, have good seasonal yield distribution, and are rust resistant. Quite possibly, variety is as important as or more important than species.

At the West Central Research and Outreach Center in Morris, we are measuring the performance of dairy cows grazing two unique pasture systems designed to maximize seasonal forage yield and quality and extend the grazing season. System 1 will increase within-field species diversity targeting perennial cool season, polyculture pastures to enhance multi-seasonal productivity (spring, summer and fall). System 2 will increase across-landscape diversity achieved by adding a combination of perennial polycultures and annual warm season grasses fertilized with livestock manures. Regional differences in soil fertility and rainfall may favor different pasture species in other locations.

Our current pasture species mixtures and seeding rates are as follows:

  1. Perennial ryegrass (4 lb), White clover (2 lb), Red clover (3 lb), and Chicory (2 lb);
  2. Orchardgrass (3 lb), Meadow fescue (6 lb), Chicory (1 lb), Alfalfa (10 lb); and
  3. Perennial ryegrass (3 lb), Meadow fescue (8 lb), White clover (4 lb), Red clover (2 lb), and Chicory (1 lb)

Grazing systems using these different approaches to achieve diversity require biological, environmental and economic analysis. In summary, pasture management and forage species selection within a farm can influence the feed quality of pasture forage for grazing dairy animals.

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