Ingestion of endophyte infected (E+) fescue by pregnant mares can cause significant reproductive problems. Plateau® and Cimarron® herbicides suppress fescue while leaving desired forages unharmed. To determine if these herbicides are harmful to pregnant mares, they were allowed to graze pastures treated with Plateau®, Cimarron®, or vehicle carrier. Pregnancies were monitored via ultrasonography, blood chemistry, and hematology. Of the components measured only creatinine differed among treatments over time (P=0.0003) and that increase was only significant in one of four studies. Two additional experiments were conducted to determine the effect of the herbicides on alkaloids within E+ fescue. A greenhouse experiment utilizing 52 pots of E+ fescue treated with Plateau®, Cimarron®, or nothing was inconclusive, as some alkaloids increased while others decreased. These results indicated that UV light may be required for normal plant death. In a field experiment 12 plots of mixed vegetation were sprayed with the same treatments, and herbicides decreased ergovaline, N-formylloline, and lysergic acid content (P=0.0460, P=0.0324, P=0.0093 respectively). In conclusion, the herbicides did not alter blood components outside physiological norms, but the alkaloids were still present in dying E+ fescue. It may be safest to remove late gestation mares until E+ fescue is completely decayed.

Ergovaline is produced by the endophyte Neotyphodium coenophialum (Morgan-Jones and Gams) in tall fescue (Schedonorus arundinacea (Schreb.) Dumort. = Festuca arundinacea Schreb.) and is blamed for a multitude of costly livestock disorders. Testing of pastures is common in both research and on farm situations. Since ergovaline is known to be unstable and affected by many variables, the objective of this study was to determine the effect of sample handling and storage on the stability of this compound. Homogeneous milled tall fescue sub-samples were analyzed for ergovaline concentration using HPLC after a range of sample handling procedures or storage. Ergovaline was unstable in milled material after 24 hours in storage, regardless of temperature. The decrease in ergovaline after 24 hours ranged from 17 to 60%. These results show that tall fescue sample handling and storage have a significant effect on ergovaline concentrations. In conclusion, accurate laboratory analysis of ergovaline content may require that samples be transported immediately to the laboratory on ice for immediate analysis. Most laboratories are not equipped for same day analysis, therefore researchers and producers should acknowledge that laboratory ergovaline results may be lower than the actual content in the field.

Tall fescue is a widely used forage grass in the eastern USA and can form a symbiosis with a fungal endophyte, which can be beneficial for the plant but can cause livestock health issues. Little is known regarding the symbiotic response to predicted climate change. To address this knowledge gap, I analyzed tall fescue variety trial data collected throughout the U.S., exploring relationships between climate variables and yield for two different fescue cultivars that were either endophyte-free or infected. This study showed no endophyte or cultivar effect on fescue yield, but identified temperature, precipitation and location as significant predictors of yield, suggesting that local conditions were more important than endophyte presence or fescue genotype for this dataset. Using a field experiment located in central Kentucky, I quantified the ecophysiological responses of four tall fescue genotypes to endophyte presence, elevated temperature and increased growing season precipitation. In this study, tall fescue genotype was as important as endophyte presence in determining ecophysiological responses to climate change treatments. My thesis illustrates that tall fescue response to climate change will depend on host genetics, the presence and genetics of the fungal endophyte symbiont, and the specific changes to the environment experienced at a site.