S. Ray Smith

Ergovaline stability in tall fescue based on sample handling and storage methods

Ergovaline is an ergot alkaloid produced by the endophyte Neotyphodium coenophialum (Morgan-Jones and Gams) found in tall fescue [Schedonorus arundinacea (Schreb.) Dumort.] and blamed for a multitude of livestock disorders. 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 ergovaline in tall fescue samples. Fresh tall fescue was collected from a horse farm in central Kentucky at three harvest dates and transported on ice to the University of Kentucky Veterinary Diagnostic Laboratory. Plant material was frozen in liquid nitrogen, milled and mixed before being allocated into different sub-samples. Three sub-samples were assigned to each of 14 sample handling or storage treatments. Sample handling included increased heat and UV light to simulate transportation in a vehicle and on ice in a cooler per standard transportation recommendations. Storage conditions included storage at 22°C, 5°C, and −20°C for up to 28 days. Each sub-sample was then analyzed for ergovaline concentration using HPLC with fluorescence detection and this experiment was repeated for each harvest date. Sub-samples exposed to UV light and heat lost a significant fraction of ergovaline in 2 h, while sub-samples stored on ice in a cooler showed no change in ergovaline in 2 h. All sub-samples stored at 22°C, 5°C, and −20°C lost a significant fraction of ergovaline in the first 24 h of storage. There was little change in ergovaline in the freezer (−20°C) after the first 24 h up to 28 days of storage but intermittent losses were observed at 22°C and 5°C. To obtain results that most closely represent levels in the field, all samples should be transported on ice to the laboratory immediately after harvest for same day analysis. If immediate testing is not possible, samples should be stored at −20°C until analysis.

Composition of Horse Diets on Cool-Season Grass Pastures using Microhistological Analysis

Grazing patterns and diet composition can be difficult to determine with horses, but are important when pastures contain species that have the potential to cause animal toxicity. The objective of this study was to determine the composition of domesticated horse diets when grazing mixed cool-season pastures using microhistology of fecal samples. Samples of tall fescue, Kentucky bluegrass, and orchardgrass were evaluated for microscopically unique characteristics from plant fragments in fecal material. Grazing studies were conducted in cool-season grass pastures in November 2006 and April 2007 in Lexington, KY. Eight mature Thoroughbred mares were placed in individual paddocks of varying botanical compositions and grazed for six days. Fecal samples from manure piles were taken from each paddock to determine diet composition. There was a high correlation between tall fescue and orchardgrass in the pasture and in the diet (0.90 and 0.80, respectively), but no correlation with bluegrass. For each percent increase of tall fescue or orchardgrass in the pasture, there was a corresponding increase of 0.44% and 0.42%, respectively, in the diet. In conclusion, microhistological analysis of plant fecal fragments showed that horses consume tall fescue and orchardgrass in similar proportions to those found in their pastures.

Effects of Sampling Time, Cultivar, and Methodology on Water- and Ethanol-Soluble Carbohydrate Profiles of Three Cool-Season Grasses in Central Kentucky

Abstract Cool‐season grasses (CSGs) accumulate variable amounts of water‐soluble carbohydrates (WSCs, monosaccharides and disaccharides, and fructans), depending on climate, time of day and year, and genotype. Fructan concentrations in CSG are sometimes estimated as the difference between concentrations of WSC and ethanol‐soluble carbohydrates (ESCs, monosaccharides and disaccharides, and variable amounts of fructan). Characterizing both WSC and ESC may improve understanding of soluble carbohydrate profiles in pastures and inform grazing management decisions, particularly for horses at risk for laminitis. Three CSG cultivars from Kentucky pastures were collected in the morning and afternoon on two springtime dates. Water‐soluble carbohydrates and ESC were extracted with water or 80% ethanol, respectively, and analyzed by high‐performance liquid chromatography (HPLC) and a colorimetric assay. Method of analysis (HPLC or colorimetry), and extraction solvent, affected the composition of WSC or ESC determined in CSG samples, demonstrating the need to consider methodology when interpreting results. Total soluble carbohydrate (mean of WSC and ESC) concentrations across cultivars and harvests were generally higher in the afternoon than in the morning, based on both HPLC (P = .0023) and colorimetric (P < .0001) analysis. The diurnal variation was mainly due to sucrose (P < .0001). Among cultivars, monosaccharides and disaccharides constituted the majority of the averaged WSC and ESC concentrations. The proportions of water‐ and ethanol‐soluble fructan (P = .0101), and fructan chain lengths detected in water and ethanol extracts (P < .0001), differed among CSG cultivars. In choosing CSG cultivars for pastures, both soluble carbohydrate composition and concentrations should be considered. HighlightsMonosaccharides and disaccharides constituted the majority of total water‐soluble carbohydrate (WSC) or ethanol‐soluble carbohydrate (ESC) in three cultivars of different cool‐season grasses collected in mid‐springtime from central Kentucky plots.Relative amounts of glucose, fructose, and sucrose detected depended on extraction parameters.Most diurnal variation in the averaged WSC and ESC concentrations was due to sucrose, not to fructan.Fructan concentration and chain length varied with cultivar.In one cultivar, short‐chain fructans were abundant in both WSC and ESC extracts. Therefore, using the difference between WSC and ESC concentrations to calculate fructan is not a correct practice.

Converting Abandoned Hayfield to Switchgrass Increases Small Mammal Relative Abundance

Abstract Switchgrass (Panicum virgatum L.) has been identified as a versatile and broadly useful bioenergy feedstock, with potential for use in coal-fired power plants as well as ethanol production. However, in order for switchgrass use to markedly influence energy production, conversion to this grass species must occur at a large scale. Little is known about the potential ecological consequences of widescale conversion of land to switchgrass. This study was conducted to identify potential effects of switchgrass planting on small mammal populations. An abandoned perennial cool season grass hayfield in central Kentucky was subdivided into two fields; one field was planted with switchgrass and the control field was maintained as an unmanaged hayfield. Small mammal relative abundance was quantified using a tracking method through the third year following switchgrass planting. Small mammal relative abundance was greater in the switchgrass field than in the control field. Vegetative community analysis showed the control field was dominated by tall fescue, suggesting that thickness of stand and/or fescue toxicity may have been a factor in reduced small mammal abundance. These data suggest that conversion of abandoned old fields to switchgrass will not have a negative effect on small mammal populations. Further research should target potential mechanisms for this variation in small mammal relative abundance, as well as other species in the community which may be affected by conversion to switchgrass.