Submitted to: Meeting Proceedings
Publication Type: Other
Publication Acceptance Date: 8/10/2005
Publication Date: 10/9/2005
Citation: Klotz, J.L., Schafer, W.D., Smith, D.K., Smith, L.L., Arrington, B.C., Bush, L.P., Strickland, J.R., Aiken, G.E., Schardl, S., Hesse, U., Dinkins, R.D. 2005. Annual progress report for USDA-ARS-FAPRU to SERA-IEG 8 Tall Fescue Toxicosis/Endophyte Workshop. Meeting Proceedings. pgs 30-36. Interpretive Summary: Non-technical summary: The following projects are reported in the annual report to SERAIEG 8. Project: Response of Bovine Vasculature to Increasing Concentrations of Lysergic Acid. Personnel: Klotz, Shafer, Smith, Smith, Arrington, Bush, and Strickland. Objective: Evaluate the vasoconstrictive effects of increasing concentrations of d-lysergic acid in the isolated bovine lateral saphenous vein. Impact: Data showed that lysergic acid is a weak vasoconstrictor (only at very high dosages) in the in vitro blood vessel screening model. As vasoconstriction is a major component of fescue toxicosis, these data indicate that lysergic acid may play a minor role in the onset of intoxication. Project: Post-Graze Heat Stress and Growth Performance of Yearling Steers Exhibiting Symptoms of Fescue Toxicosis. Personnel: Aiken. Objective: An experiment was conducted to determine the effects of pasture supplementation and post-graze implantation on weight gain and changes in rectal temperature and serum prolactin following grazing and placement on a fescue-free diet. Results: Average daily gain on pasture was higher with supplementation (0.45 kg/d) than without (0.66 kg/d). At termination grazing (23 Sept.), 97.5% of the cattle had rough haircoats. Serum prolactin increased rapidly between 0 and 20 d and stabilized for the remainder of the pen phase. Initial rectal temperature averaged 40.2oC and was not affected by supplementation, but declined to 39.2 oC by day 5. Least square means, adjusted for initial BW, for ADG and final BW of implanted steers were higher with pasture supplementation (2.28 kg/d and 443 kg, respectively) than without (1.83 kg/d and 413 kg). Furthermore, least square means for ADG and final BW for steers without pasture supplemenation were higher with implantation than without (1.42 kg/d and 382 kg). Project: Fescue-Endophyte Sequencing. Personnel: Schardl, Dinkins, and Hesse. Objective: This project is aimed at addressing the hypothesis that different tissues and stages in host plant development entail different host responses to endophytes and vice versa, and that many such responses are manifested at the level of gene expression. Results: Sequence analysis of fescue and fescue/endophyte plants revealed a high number of single copy cDNAs. Of the 24,000 sequencing reactions, we have determined that 15,641 are unique sequences, or unigenes. A subsample of genes have shown that approximately 70% of the genes have homology to known plant genes, 17% with homology to fungal genes and 13% of which the origin is unknown or previously uncharacterized. Impact: From the sequences, plant and fungal unigene sets will be identified, and replicate microarrays will be produced for each. These will be hybridized to probes from various tissues of endophyte-symbiotic and aposymbiotic plants. The results will indicate profiles of plant gene expression in response to endophyte, and of endophyte gene expression in response to developmental changes in the plant as well as to different environmental conditions. Such results should provide clues as to the mechanisms of host benefits conferred by the endophytes, and the remarkable stability of the grass-endophyte symbiose
Technical Abstract: Annual Progress REport SERAIEG8 Tall Fescue Toxicosis/Endophyte Workshop See Interperative Summary for more information.