|JOHNSON, JENNIFER - University Of Kentucky|
|PHILLIPS, TIM - University Of Kentucky|
|BARRETT, MIKE - University Of Kentucky|
|SCHRICK, F. - University Of Tennessee|
Submitted to: International Symposium on Fungal Endophytes of Grasses
Publication Type: Abstract Only
Publication Acceptance Date: 6/4/2010
Publication Date: 6/28/2010
Citation: Johnson, J.M., Aiken, G.E., Phillips, T., Barrett, M., Schrick, F.N. 2010. Grazing Evaluation of a Novel Endophyte Tall Fescue Developed for the Upper Transition Zone. International Symposium on Fungal Endophytes of Grasses. pp 52-53.
Technical Abstract: An endophyte (Neotyphodium coenophialum) infests tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] that imparts tolerances to moisture, heat, and grazing, but also produces ergot alkaloids that are toxic to grazing cattle. Novel endophytes have been developed that do not produce toxic ergot alkaloids. A 2-yr grazing experiment evaluated steer performance and physiology, and forage productivity of KYFA9301 infected with AR584 novel endophyte (AR584) as compared to KY31 wild-type endophyte (KY31), endophyte-free KYFA9301 (EF9301) and ‘Jesup’ fescue infected with AR542 novel endohyte (MaxQ). Fescue-endophyte combinations were assigned to 1.0-ha pastures in a randomized complete block design with three replications. Pastures were continuously grazed from 6 May to 23 July in 2008 and from 2 April to 25 June in 2009. Rectal temperatures were recorded and jugular blood was collected for assaying serum prolactin. Stocking rates were varied to maintain similar forage masses (2500 ± 250 kg DM ha-1). Average daily gain was lowest (P < 0.01) for KY31 [0.66 ± 0.05 (SEM) kg d-1], and was similar (P > 0.10) among EF9301 (0.80 ± 0.05 kg d-1), NE9301 (0.81 ± 0.08 kg d-1) and MaxQ (0.84 ± 0.04 kg d-1). Rectal temperatures were elevated (P < 0.05) in steers grazing KY31 as compared to those grazing AR584, MaxQ, and EF9301. Serum prolactin concentrations were similar (P > 0.15) for EF9301, NE9301, and MaxQ pastures, and these were greater than for KY31 pastures. By termination of grazing, stocking rates were highest (P < 0.001) in KY31 pastures, and rates in MaxQ pastures were less (P < 0.05) or tended (P < 0.15) to be less than EF9301 and AR584, respectively. Results indicated that KYFA9301 infected with the AR584 endophyte can improve weight gain and alleviate toxicosis, and provide higher carrying capacities than MaxQ in the early summer.