|Johnson, Jennifer -|
Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: July 28, 2010
Publication Date: September 1, 2010
Citation: Johnson, J.M., Aiken, G.E. 2010. Grazing evaluation of a novel endophyte tall fescue developed for the upper transition zone. Agricultural Experiment Station Publication. Pgs. 21-26. Interpretive Summary: Tall Fescue is a cool-season perennial bunchgrass that has been utilized in the United States for decades. Kentucky 31 has become the most commonly used and economically important perennial grass in the US. Tall fescue is widely adapted and is persistent under poor management. These superior agronomic qualities have been associated with the presence of an endophytic fungus, which also has been linked to fescue toxoicosis. This malady typically reduces growth rates and increases core body temperature and respiration rates, and decreases prolactin concentrations. Novel endophyte strains have been suggested to provide the desirable agronomic qualities without the negative side-affects to grazing animals. A grazing study evaluated the steer performance and forage productivity of a late-maturing experimental population (KYFA9301) infected with the AR584 novel endophyte in comparison to Kentucky 31, ‘Jesup’ MaxQ, and endophyte-free KYFA9301. Results indicated that steer weight gains were improved, and negative side-effects were not detected in those steers grazing the new experimental population when compared to toxic Kentucky 31 tall fescue. Results indicated KYFA9301 tall fescue provided animal performance and pasture productivity that make it a viable option for alleviating the negative effects caused by grazing toxic Kentucky 31 tall fescue.
Technical Abstract: A grazing experiment determined that a late-maturing tall fescue developed by University of Kentucky has potential for grazing in the U.S. upper transition zone. Steers were grazed in a 2-yr experiment using variable stocking rates to compare steer performance and physiology, and forage productivity of KYFA9301 infected with the nontoxic AR584 novel endophyte (NE9301) with Kentucky 31 infected with the toxic wild-type endophyte (KY31), endophyte-free KYFA9301 (EF9301), and ‘Jesup’ infected with non-toxic AR542 (MaxQ). Fescue-endophyte combinations were assigned to 1.0-ha pastures in a randomized complete block design with three replications. Average daily gains among nontoxic fescues were similar and greater than KY31. Rectal and skin temperatures, and prolactin concentrations were similar among the nontoxic fescues and were improved relative to those for KY31. Stocking rates in the latter half of the grazing were highest for KY31, were higher for EF9301 than for MaxQ and NE9301, and tended to be higher for NE9301 than for MAXQ. Results indicate that KYFA9301 supports higher stocking rates in the late spring and early summer than MaxQ to make it an option to KY31 in the upper transition zone.