Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2006
Publication Date: 7/25/2006
Citation: Coblentz, W. K., K. P. Coffey, T. F. Smith, D. S. Hubbell, III, D. A. Scarbrough, J. B. Humphry, B. C. McGinley, J. E. Turner, J. A. Jennings, C. P. West, M. P. Popp, D. H. Hellwig, D. L. Kreider, and C. F. Rosenkrans, Jr. 2006. Using orchardgrass and endophyte-free fescue versus endophyte-infected fescue overseeded on bermudagrass for cow herds: four-year summary of forage characteristics. Crop Science. 46:1919-1928. Interpretive Summary: Toxins produced by the fungus associated with tall fescue forages are known to limit livestock performance in the southeastern US, especially during summer months. Animal performance throughout this region could be improved by utilizing non-toxic, cool-season perennial forages, but (historically) these forages have not persisted adequately in the southern Ozarks. In this study, toxic, endophyte-infected tall fescue was killed with a single application of glyphosate, and either non-toxic orchardgrass or endophyte-free tall fescue forage was established with no-till seeding techniques. Intensive grazing management was then used throughout a 4-year cow-calf grazing trial to maintain these non-toxic forages within these pastures. Generally, the rotational grazing strategies utilized in these studies coupled with the strict avoidance of overgrazing were effective at maintaining populations of endophyte-free fescue and orchardgrass, and at limiting the competitiveness of the base sod of bermudagrass. Conditions regulating reinfection of renovated pastures remain incompletely defined, and threshold levels of toxicity and/or dilution required to affect livestock performance either negatively or positively remains equally unclear. Pasture mixtures of endophyte-infected tall fescue and bermudagrass are common throughout the southern Ozarks; however, the toxicity loads within these pastures can be reduced substantially for at least five years with a single application of glyphosate followed by establishment of non-toxic perennial cool-season forages.
Technical Abstract: A systems trial was designed to evaluate forage characteristics within mixed-species pastures consisting of: i) endophyte-infected tall fescue (Festuca arundinacea Schreb.; E+) mixed with common bermudagrass [Cynodon dactylon (L.) Pers.] and other forages; ii) endophyte-free tall fescue (E-) overseeded into dormant common bermudagrass; and iii) orchardgrass (OG; Dactylis glomerata L.) established under the same conditions as E-. The E- and OG pastures were grazed with either twice weekly (2W) or twice monthly (2M) rotation schedules, but E+ was grazed only as 2M. Over 41 sampling dates (2000 through 2003) the mean forage mass across all forage systems was 3809 kg ha-1, and there was an interaction of forage system and sampling date (P = 0.001). In vitro dry matter disappearance (IVDMD) and crude protein (CP) varied (P < 0.0001) with sampling date in seasonal patterns that were generally predictable. Frequencies of tall fescue in E- and E+ pastures increased (P < 0.10) over years, reaching numerical maxima (61 to 72%) at the end of the trial. For OG, frequencies reached numerical maxima of 52 and 42% in 2W and 2M pastures, respectively, but then declined (P < 0.10) over time, ending at 39 and 24%, respectively. At the end of the trial, reinfection of OG pastures by rogue E+ plants reached a numerical maximum frequency of only 10%, and concentrations of total ergot alkaloids in tall fescue plants from E- pastures were only about 25% of those for E+ pastures, thereby suggesting that pasture toxicity can be reduced substantially for at least five years using these alternative forage systems.