Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2011
Publication Date: 9/1/2011
Citation: Brink, G.E., Soder, K.J. 2011. Relationships among sward characteristics and herbage intake of grazed temperate grasses. Crop Science. 51:2289-2298.
Interpretive Summary: Cool-season grasses are the primary component of pasture-based dairy systems. The more grass that dairy cows are able to consume while grazing, the more milk will generally be produced. The characteristics of these grasses that may influence consumption include their yield, height, nutritive value, and distribution of the leaf and stem fraction throughout the canopy. Our study determined which characteristics have the most influence on intake by grazing cattle in order to better understand how productivity of grazing cattle can be improved. We found that the characteristic of a pasture most relevant to consumption is the quantity of leaves available to the cattle. This trait was more important than the total yield, height, and nutritive value of the pasture.
Technical Abstract: Differences in sward structure influence intake by grazing cattle. Our objective was to determine relationships between dry matter intake (DMI) and sward characteristics of four diverse temperate grasses grazed by dairy heifers. Meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], orchardgrass (Dactylis glomerata L.), quackgrass [Elymus repens (L.) Gould], and reed canarygrass (Phalaris arundinacea L.) were grazed by four heifers at a vegetative stage during 1-week periods of the spring, summer, and fall of two years at a forage allowance two to three times the expected daily intake of dairy heifers. Dry matter yield and sward height were measured pre- and post-grazing, and pre-graze canopy structure and nutritive value were measured in 5-cm increments.There were few differences in DMI among the grasses in the spring of either year (mean of 610 and 420 kg/ha/d). In the summer, DMI was greatest on orchardgrass (720 kg/ha/d) and in the fall, DMI was greatest on meadow fescue and orchardgrass (mean of 760 kg/ha/d). Although a minor portion of the sward, the stem fraction increased with canopy depth of all grasses. Nutritive value of meadow fescue was generally greater than that of the other grasses. At vegetative stage, DMI of these grasses was most highly correlated with leaf yield of the canopy layers grazed by cattle (R2 = 0.66). The results indicate that the quantity of leaves in the canopy has the greatest influence on grazing intake of vegetative grasses.