Submitted to: Forage and Grazinglands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 5, 2012
Publication Date: June 28, 2012
Repository URL: http://handle.nal.usda.gov/10113/56493
Citation: Brink, G.E., Casler, M.D. 2012. Yield and nutritive value differences among cool-season grasses. Forage and Grazinglands. DOI:10.1094/FG-2012-0619-01-RS. Interpretive Summary: Because grasses lose nutritive value as they mature, pasture management is often a balancing act between letting the plants grow long enough for adequate growth but not so long that the nutritive value declines appreciably. The leaf portion of a grass has more nutrient value than the stem, and livestock prefer to consume the leaf portion; but the leaf’s contribution to forage growth depends on the type of grass and season of the year. Depending on the location, a wide variety of cool-season grasses are used in pastures. We conducted a study to determine what differences in growth and nutritive value exist among the grasses typically grown in the Northeastern and Midwestern United States. These grasses were grown in two different environments and sampled during the spring, summer, and fall. We found that nutritive value of grass leaves declines slightly in the spring, but changes little during the summer and fall. The production of stems during the spring was the primary factor contributing to the increase in yield and decline in quality of the total forage. Meadow fescue and timothy generally maintained the highest nutritive value. Depending on livestock nutrition needs, producers should utilize most grasses before appreciable stems are produced in the spring. Pasture management during the remainder of the season can be flexible because nutritive value changes very little. This information will help grazing-based livestock producers better manage their pasture grasses for both adequate growth and nutritive value.
Technical Abstract: Grasses are typically utilized at a vegetative stage of maturity under managed intensive rotational grazing. We compared the yield and nutritive value of the leaf and stem fraction, and total herbage of eight erect-growing, perennial cool-season grasses during 30-day intervals in the spring, summer, and fall at two Wisconsin locations. Total herbage production of all grasses was greatest during the spring, as expected, but, with the exception of smooth bromegrass, differences in leaf yield were relatively small. During the summer and fall, endophyte-infected and endophyte-free tall fescue produced the greatest leaf yield, and quackgrass and smooth bromegrass the least. Significant leaf crude protein (CP) concentration differences among the eight grasses occurred during the spring, summer, and fall, but leaf CP of all grasses exceeded 16% and any differences would likely be inconsequential. Lowest neutral detergent fiber (NDF) and greatest NDF digestibility were measured in leaves of meadow fescue or timothy. Because yield differences among these grasses during the spring can be attributed primarily to the stem fraction, and spring yield constitutes a large proportion of annual yield, a producer’s perception of value to a grazing system may be biased by total yield estimates. The greater nutritive value of grasses like meadow fescue must be balanced against slightly lower productivity.