Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2007
Publication Date: 9/1/2007
Citation: Brink, G.E., Casler, M.D., Hall, M. 2007. Canopy structure and forage quality differences among temperate grasses. Crop Science. 47:2182-2189. Interpretive Summary: A wide range of cool-season grasses are available to farmers who employ a grazing-based system to feed dairy cattle. Although total yield is a typical measure of grass productivity, little is known about the distribution and quality of forage from the top to the bottom of the canopy, a property that may more accurately reflect what is consumed by the grazing animal. When measured at a height representing typical grazing management (10 inches), we found significant differences in the canopies of Kentucky bluegrass, perennial ryegrass, orchardgrass, timothy, tall fescue, soft-leaf tall fescue, meadow fescue, smooth bromegrass, reed canarygrass, and common quackgrass. Timothy, smooth bromegrass, and quackgrass produced more forage in the upper and middle portions of the canopy than perennial ryegrass and meadow fescue in the spring, but the opposite was true in the summer. Forage quality declined from the top to the bottom of the canopy in most grasses, but digestibility of perennial ryegrass, timothy, and meadow fescue was unchanged. The results suggest that depending on the grasses present and the season of the year, producers can improve utilization of high quality pasture forage by increasing or decreasing the quantity of forage consumed.
Technical Abstract: Grass canopy structure may influence grazing behavior and intake of grazing animals. Our objective was to determine the vertical distribution of dry matter (DM) and quality within swards of diverse temperate grasses. The study was conducted on swards of 10 temperate grasses in 2004 and 2005 on a Loyal silt loam (fine-loamy, mixed, superactive, frigid Oxyaquic Glossudalf). When mean canopy height of each grass reached approximately 25 cm during the spring, summer, and fall, the sward was harvested by layers: 20 to 25, 15 to 20, and 10 to 15 cm. Differences in DM distribution among and within grass canopies were influenced by season. Quackgrass [Elytrigia repens (L.) Nevski], smooth bromegrass (Bromus inermis Leyss.), and timothy (Phleum pratense L.) produced more DM in the upper and middle portions of the canopy than orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), and meadow fescue (Festuca pratensis Huds.), while the opposite occurred in the summer. From the top to the bottom of the canopy, mean crude protein and neutral detergent fiber digestibility (NDFD) decreased 5% and 3%, respectively, except in perennial ryegrass, timothy, and meadow fescue, where NDFD was unchanged. These results suggest that at equivalent heights, significant differences in canopy structure exist among temperate grasses, and that forage quality differences between canopy layers may permit greater utilization of some grasses than others without forcing the animal to consume poorer quality forage.