Grass mixtures for Midwest horse pastures
Introduction: In the Midwest and Eastern U.S., cool-season grasses are the foundation of productive pastures. Horses are known to be selective grazers and can graze forage species to a shorter height compared to other livestock, which may limit the productivity and survival of some pasture species. This grazing behavior not only affects uniform utilization of forage species, but forage persistence and yield, especially if preferred species are repeatedly grazed. Although individual cool-season grass species have been evaluated for horse preference and forage yield and persistence under horse grazing, there is no research investigating these characteristics in commercially available cool-season grass mixtures. A better understanding of the response of commercial grass pasture mixtures to horse grazing will aid horse owners in selecting an ideal grass pasture mix.
Objective: The objectives of this research were to evaluate horse preference, yield and species persistence of cool-season grass mixtures under horse grazing.
Figure 1. Horses grazing cool-season grass pasture mixtures
Materials and methods: Eight commercially marketed perennial cool-season grass mixtures were grazed by four adult horses (Figure 1). All mixtures contained four to six cool-season perennial grass species (Table 1). Species population density measurements were taken each spring and fall and yield was mechanically measured before each grazing. A subsample of forage was collected and dried to determine dry matter content; yield is presented on a dry matter basis. Post grazing, horse preference was determined by visually assessing percentage of forage removal on a scale of 0 (no grazing) to 100 (100% of vegetation removed).
Figure 2. Changes in species populations as affected by initial planting rates and growing season under horse grazing in Minnesota. Click to enlarge.
Results: Horses preferred mixtures containing endophyte-free tall fescue, perennial ryegrass, Kentucky bluegrass and timothy and had less preference for mixtures containing ≥30% orchardgrass (Table 1). Preference is an important measurement since a more preferred mixture will result in more uniform grazing, thus increasing forage utilization and decreasing maintenance (i.e. mowing). Mixtures had similar forage yields that ranged from 2.7 to 3.2 tons per acre (Table 1). After two years of grazing, populations of orchardgrass and endophyte-free tall fescue increased from initial percentage of the mixtures, Kentucky bluegrass remained constant and meadow fescue and perennial ryegrass had the greatest rate of decline (Figure 2). Orchardgrass became the dominate species, regardless of initial percentage in the mixture. Mixtures containing endophyte-free tall fescue, perennial ryegrass, Kentucky bluegrass and timothy should be planted in Midwestern U.S. horse pastures; however, mixtures will likely transition to endophyte-free tall fescue and Kentucky bluegrass dominated pastures over time.
Take home message: Planting mixtures similar in composition to Agassiz CHS #4 and La Crosse BLM #4 should result in a high yielding, persistent and preferred grass pasture for horses in the Midwest U.S.
Table 1. Initial composition, forage yield (ton per acre) and preference (percent removal) of eight cool-season grass mixtures grazed by horses in Minnesota.
|Mixture||Species||Initial mixture composition (%)||Yield (tons/acre)||Preference
|Agassiz CHS #4||Tall Fescue||40||3.1||88|
|Agassiz MN-G||Meadow Bromegrass||30||3.2||45|
|CR Heavy||KY Bluegrass||45||2.7||46|
|CR Light||KY Bluegrass||40||3.1||48|
|Dan Patch||KY Bluegrass||40||3.0||59|
|La Crosse BLM #4||Perennial Ryegrass||30||2.8||91|
|Waconia Mix||KY Bluegrass||35||3.1||63|
2016, Reviewed by Harlan Anderson, Ron Genrick, John Strohfus and Dan Foor