Relationship between Herbage Intake and Sward Structure of Grazed Temperate Grasses
- Geoffrey E. Brink *a and
- Kathy J. Soderb
Temperate grasses differ in sward structure, which may influence herbage intake of grazing cattle. We compared herbage intake of meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], orchardgrass (Dactylis glomerata L.), quackgrass [Elymus repens (L.) Gould], and reed canarygrass (Phalaris arundinacea L.) grazed by dairy heifers, and determined its relationship with sward structure. Grasses were grazed at vegetative stage for 24 h over 5-d periods in the spring, summer, and fall of 2 yr. Forage dry matter (DM) allowance was a minimum of two times expected daily intake (11 kg animal−1 d−1). Sward characteristics were measured before grazing (height, mass, vertical distribution of leaf and stem bulk density and nutritive value). Herbage DM intake was estimated daily (pregraze minus postgraze herbage mass). Despite species differences in pregraze sward height (range of 29–49 cm across seasons), herbage mass (range of 1480–2540 kg DM ha−1), and neutral detergent fiber (NDF) digestibility (range of 713–843 g kg−1 NDF), no differences in leaf bulk density and herbage intake were found among grasses during four of six grazing seasons. Herbage intake differences during two seasons were related to either sward leaf bulk density (r = 0.79) or stem bulk density (r = −0.84), and the associated changes in leaf and stem mass of the canopy layers grazed by cattle, indicating that these sward characteristics were the primary determinants of grazed herbage intake in vegetative meadow fescue, orchardgrass, quackgrass, and reed canarygrass.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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