Grazing Evaluation of a Novel Endophyte Tall Fescue Developed for the Upper Transition Zone.

A wild-type endophyte (Neotyphodium coenophialum) that infests tall fescue (Lolium arundinaceum) improves plant tolerance to drought, heat, and grazing stresses, but also produces ergot alkaloids that adversely affect performance and physiology of cattle. Novel endophytes can impart improved stress tolerance to increase fescue persistence and productivity, without the toxic ergot alkaloids.  A 2-yr grazing experiment is being conducted with yearling steers to evaluate steer performance/physiology and forage quality/productivity with a novel endophyte tall fescue, AR584-KYFA9301 (NE9301; not commercially released), compared to AR542-‘Jesup’ (MaxQ), endophyte-free KYFA9301 (EF9301), and wild-type ‘Kentucky 31 (KY31) tall fescues.  Entries were assigned to 1.0-ha pastures in a completely randomized design with three replications.  Pastures were planted in September of 2006.  Grazing with variable stocking (4 testers) was initiated in May 2008 and terminated in July 2008.  Shrunk bodyweights were taken at the beginning (mean bodyweight = 304 ± 34 kg) and end of the grazing season.  Rectal and skin temperatures were recorded on days 28, 56, and 77.  Average daily gains among MaxQ (0.87 kg d^-1), NE9301 (0.74 kg d^-1), and EF9301 (0.74 kg d^-1) were similar (P > 0.10), and these were greater (P < 0.05) than KY31 (0.57 kg d^-1).  Rectal and skin temperatures among NE9301, EF 9301, and MaxQ were similar (P > 0.10), and these were less (P < 0.05) than KY31.  Carrying capacities were similar (P > 0.10) among entries (431 ± 19 steer d ha^-1).  Results in the first year indicated steer performance and body temperature responses for NE9301 and EF9301 were similar to those for MaxQ.