HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Griffin, J. L. Articles by Jung, G. A. Search for Related Content PubMed Articles by Griffin, J. L. Articles by Jung, G. A. Agricola Articles by Griffin, J. L. Articles by Jung, G. A.

Forage Quality Evaluation of Two Warm–Season Range Grasses Using Laboratory and Animal Measurements¹

The shortage of available forage during mid–summer is considered a major factor limiting the size of beef cowcalf herds in the Northeast. Consequently, using warmseason perennial range grasses as a supplement to existing cool–season grass forage programs is being considered. Animal feeding trials were conducted to assess the forage quality of ‘NY 1145’ big bluestem (Andropogon gerardi Vitman), and ‘Blackwell’ switchgrass (Panicum virgatum L.) grown in Pennsylvania. Laboratory and animal estimates of digestibility were compared.

Warm–season grass hays harvested at early head emergence, 2 weeks later, and at a regrowth stage in fall were fed with protein supplement to growing wether sheep in the first trial. In vivo digestible dry matter (DDM) of the hays ranged from 67 to 74%. Big bluestem and switchgrass DDM decreased 0.50 and 0.36 percentage units/ day, respectively, when harvest was delayed 2 weeks after head emergence, but dry matter intake (DMI) was not affected. Warm–season grass DDM and DMI were equal or superior to those for summer or fall harvested ‘Ky 31’ tall fescue (Festuca arundinacea Schreb.). In the second trial, DDM of big bluestem and switchgrass hays harvested at early head emergence and fed to mature wether sheep without protein supplement ranged from 56 to 69%. Digestible dry matter and DMI for the warm–season grasses were generally lower than those for tall fescue harvested in spring at the same growth stage.

In both animal studies, rankings of the grass hays using in vitro dry matter digestibility (IVDMD) and DDM estimates did not differ. The IVDMD technique did underestimate DDM by approximately 17 percentage units. This emphasizes the importance of animal evaluation in supporting laboratory forage quality analyses. Results suggest that big bluestem and switchgrass forage, harvested at early head emergence or later, appear most suitable for animals with lower nutrient requirements, such as beef cows.

Key Words: Andropogon gerardi Vitman • Panicum virgatum L. • Big bluestem • Switchgrass • Digestible dry matter • Dry matter intake

² Former graduate research assistant, Pennsylvania State Univ., presently assistant professor of agronomy, Rice Exp. Stn., Louisiana State Univ., Crowley, LA 70526; associate professor of animal nutrition, Pennsylvania State Univ., University Park, PA 16802; and research agronomist, U.S. Regional Pasture Res. Lab., University Park, PA 16802, respectively.

Received for publication November 19, 1979.