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.
There has been increased interest in using switchgrass (Panicum virgatum) as a biomass crop. There are several challenges to developing this industry, and these have led to the potential use of switchgrass as hay for feeding beef cattle in Kentucky. The effect of increasing maturity on concentrations of CP, NDF, ADF, and other nutritive value indicators of switchgrass hay is well documented, but few in vivo intake and digestibility trials have been conducted to assess this effect on beef cattle performance. The objective of this research was to evaluate the effect of increasing plant maturity on DMI, apparent digestible DMI, and DM digestibility, and to investigate potential challenges for producers when incorporating switchgrass hay into their forage rotation for feeding beef cattle. Two in vivo intake and digestibility trials were conducted in 2011 in which Angus × Hereford beef steers (199.5 to 264.9 kg) were fed ad libitum Alamo and Cave-in-Rock switchgrass harvested as late vegetative, boot, and early flowering hay. Dry matter intake decreased by 1.0 and 0.6% of BW from late vegetative to early flowering stages with Alamo and Cave-in-Rock cultivars, respectively. Similarly, DM digestibility decreased by 15.9 and 18.5% and digestible DMI decreased by 1.0 and 0.6% of BW. Observed decreases in nutritive value, DMI, apparent digestible DMI, and DM digestibility indicate that producers should harvest Alamo and Cave-in-Rock switchgrass before it reaches the boot stage of maturity.
Central Kentucky horse pastures contain significant populations of tall fescue (Schedonorus arundinacea (Schreb.) Dumort) infected with an endophyte (Epichloë coenophialum (Morgan-Jones and Gams) Bacon and Schardl) known to produce several ergot alkaloids, with ergovaline in the highest concentration. While most classes of horses are not adversely affected by average levels of ergovaline in pastures, late term pregnant mares have a low tolerance to ergovaline and the related ergot alkaloids. Endophyte-infected tall fescue has been known to cause prolonged gestation, thickened placenta, dystocia, agalactia, and foal and mare mortality. The University of Kentucky Horse Pasture Evaluation Program utilizes ergovaline and endophyte testing, as well as pasture species composition, to calculate ergovaline in the total diet in broodmare pastures. This data is used to develop detailed management recommendations for individual pastures. Application of these recommendations has led to reduced tall fescue toxicity symptoms on these farms, as well as improved pasture management and improved forage quality and quantity.
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