Forage Nutritive Value and Preference of Cool-Season Grasses under Horse Grazing

Cool-season grasses are rarely evaluated under horse grazing. The objectives of this study were to evaluate preference and forage nutritive value of cool-season grasses while grazed by horses (Equus caballus L.). Research was conducted in 2010 and 2011 in Minnesota. Four horses rotationally grazed tall fescue [Schedonorus phoenix (Scop.) Holub], meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], quackgrass [Elymus repens (L.) Gould], smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (Bromus biebersteinii Roem. & Schult.), reed canarygrass (Phalaris arundinacea L.), perennial ryegrass (Lolium perenne L.), timothy (Phleum pratense L.), Kentucky bluegrass (Poa pratensis L.), creeping foxtail (Alopecurus arundinaceus Pior.), and orchardgrass (Dactylis glomerata L.) monthly during the growing season. Kentucky bluegrass, timothy, and meadow fescue were the most preferred grasses, with most grazing events removing >60% of the available forage, while meadow bromegrass, creeping foxtail, reed canarygrass, and orchardgrass were less preferred, with grazing removing <50% of available forage (P <= 0.0027). Perennial ryegrass, quackgrass, and smooth bromegrass had a higher concentration of crude protein than Kentucky bluegrass, orchardgrass, creeping foxtail, or timothy (Poa 0.0027). Quackgrass had a lower neutral detergent fiber (NDF) concentration than creeping foxtail or smooth bromegrass (P = 0.0001). Perennial ryegrass and meadow fescue were higher in NDF digestibility, while creeping foxtail and Kentucky bluegrass were lower (P = 0.0001). Timothy, Kentucky bluegrass, meadow fescue, and perennial ryegrass had higher nonstructural carbohydrate (NSC) concentrations than meadow bromegrass, orchardgrass, or reed canarygrass (P= 0.0001). Horses showed distinct preferences among grasses; however, only NSC was positively correlated with horse preference.