Herbage mass, botanical composition, forage nutritive value, and preference of grass–legume pastures under horse grazing

Cool-season perennial grasses are the foundation of productive horse pastures in the north-central United States. The addition of legumes in pastures can increase forage mass and digestible energy content, yet little research has investigated grass–legume pastures under horse grazing. The objectives of this research were to evaluate herbage mass, botanical composition, forage nutritive value, and preference of grass–legume pastures under horse grazing. Plots consisting of orchardgrass (Dactylis glomerata L.), Kentucky bluegrass (Poa pratensis L.), and meadow fescue (Festuca pratensis Huds.) were planted in monoculture and in binary mixtures with alfalfa (Medicago sativa L.) or white clover (Trifolium repens L.) and grazed by horses in Minnesota during the 2013, 2014, and 2015 grazing seasons. Herbage mass, weed mass, and forage nutritive values were determined prior to grazing, and horse preference was evaluated following grazing. When evaluating herbage mass, the inclusion of alfalfa resulted in a consistently higher mass than grass monoculture. Kentucky bluegrass mixtures resulted in a decreased mass of non-sown (weed) species and an increase in horse preference. Improved forage nutritive values were also observed with the inclusion of legumes regardless of grass species, including higher crude protein and neutral detergent fiber digestibility at 48 h and lower neutral detergent fiber. As a result, using grass–legume mixtures in pastures can provide benefits for grazing horses and pasture productivity.