Fescue Toxicosis occurs when animals are fed or grazing on Tall Fescue (Festuca arundinacea) syn. (Lolium arudinacea [Schreb]) grass that is infected with the endophytic fungus Neotyphodium coenophialum (Bacon et al., 1977). This disease affects cattle, sheep, and horses causing reduced feed consumption, average daily gain (ADG), and reproductive performance (Hoveland, 2003). The disease is caused by ergot alkaloids within the fungus, which lives in the plant (Hoveland et al., 1980). Fescue toxicosis is a major concern because at least 35 million acres in the United States contain Tall Fescue (Faulkner, 1999); areas impacted include southern Illinois, Kentucky, Tennessee, northern Mississippi, northern Louisiana, Georgia, West Virginia, Arkansas and Missouri and in some areas of the Pacific coast such as Oregon (Roberts et al., 2004). Due to the effects of this disease, producers lose an estimated 609 million dollars per year (Paterson et. al, 1995). The aim of this research project was to determine if the herbal supplement, Blessed Thistle, could be used to counteract the effects of fescue toxicosis in cattle. Eighteen Angus first calf heifers and their calves were divided into three treatment groups (n = 6); negative control fed non-endophyte infected Max Q hay (EN), positive control fed endophyte infected KY-31 fescue hay (E+), or treatment fed KY-31 fescue hay and Blessed Thistle extract (E+/BT). Heifers fed E+/BT diet maintained pretreatment prolactin levels throughout the study. Additionally, the change in prolactin levels E- and E+/BT were not significantly different suggesting a protective effect from the blessed thistle. The change in heifer BCS was insignificant except for the E+/BT group which was significantly different (P = 0.02) before and after. The differences between the calf weights were trending (P = 0.088) indicating the ability of the E+/BT calves to perform similarly to the E- calves. The milk production estimate was insignificant (P = 0.497). The rectal temperatures data indicated a difference at the beginning and end of the study (P < 0.001). However, no differences were detected between treatment groups. These results suggest that Blessed Thistle can ameliorate some symptoms of fescue toxicosis however, further research is needed.

Visceral toxicosis of catfish (VTC) is a sporadic, often devastating disease in catfish aquaculture, caused by botulinum neurotoxin serotype/E (BoNT/E). The median lethal dose of BoNT/E for channel catfish (Ictalurus punctatus) fingerlings is 13.7 pg/fish. The diagnosis of VTC is suspected if clinical signs and lesions are produced when affected serum is injected into sentinel-catfish and confirmed if this effect is neutralized with BoNT/E antitoxin. However, the assay is complicated in diagnostic cases by small serum samples from affected fish, lack of standardization and availability of small catfish (~10g). Therefore a zebrafish (~0.4g) bioassay for VTC diagnosis was tested and validated. Susceptibility was tested with other serotypes of toxin to help establish zebrafish as a diagnostic model for BoNTs. BoNT/E consist of100kD heavy chain (HC) and 50kD light chain (LC) linked by a disulfide bond. The HC transports the LC into the cytosol of the neuron, where LC (Zn2+-endoprotease) cleaves the SNAP-25 protein thereby blocking the signal transduction at the neuromuscular junction. The HC-based vaccines can induce protective immunity in mammals. To evaluate HC immunogenicity in catfish, rBoNT/E/HC vaccine produced by USAMRIID was tested; this vaccine did not induce a robust antibody response, but western blot analysis demonstrated specific antibody production in 3 of 11 vaccinated fish. We then developed four channel catfish virus (Ictaluridherpesvirus 1, CCV) recombinants expressing synthetic BoNT/E/HC using our established Gateway CCV recombination system to determine if the virus vector could improve the response. Catfish were vaccinated with these recombinants or with a control vector that expressed Escherichia coli beta-galactosidase (CCV-lacZ). No significant protective immunity or BoNT/E antibodies were observed but CCV-lacZ induced a strong antibody response. These results suggest that BoNT/E/HC has low immunogenicity in channel catfish and deviates from the high immunogenicity observed in mammals. To develop a protective vaccine for VTC, it will be necessary to enhance the BoNT/E /HC immunogenicity in channel catfish. Development of recombinant animals which are resistant to BoNT/E was explored as another potential way to prevent VTC. However, the attempts to modify SNAP-25 of zebrafish by genome editing using Transcription Activator-Like Effector Nucleases were unsuccessful.

No description available.

The objectives of this study were to document the negative effects of endophyte-infected fescue consumption on cow physiological responses after stress challenge and to assess the ability of blessed thistle to ameliorate these responses. Twenty -seven Angus crossbred cows approximately 5-7 years of age and a body weight of (634 ± 80 kg) were equally divided into 3 treatments. Each treatment was divided into 3 replicates, leaving pens of 3 cows per treatment replicate. Each pen was balanced for initial body weight and low age. Each experimental group was randomly assigned to one of three replicates and one of three treatment dietary regimens: control/endophyte-free (EF) fescue, endophyte-infected (EI) fescue, endophyte-infected fescue + blessed thistle supplementation (EIBT). Ergovaline, one alkaloid compound thought to be deleterious in the endophyte-infected fescue metabolites was detected in EI seed analysis performed before the trial commenced. Endophyte-free seed samples were negative for total ergot alkaloids. No treatment interaction was observed for heart rate, body temperature, prolactin and urinary alkaloid analysis rate (P >0.05). A replicate interaction was observed for prolactin (P <0.05). There was an effect of stress point between before and after samples taken on D-1 and D 29 on body temperature, heart rate and cortisol (P <0.05). Results suggest treatments were ineffectual at inducing symptoms of fescue toxicosis. The full capability of blessed thistle to ameliorate symptoms of fescue toxicosis may not be fully represented in this study. Further research and knowledge into the mechanism by which fescue toxicosis impacts health and productivity of livestock is needed to develop sustainable treatment regimens.

Fescue toxicosis is a common problem in beef cattle grazing endophyte-infected (E+) tall fescue. Symptoms include decreases in feed intake, weight gain, and reproductive efficiency along with vasoconstriction. The mechanisms by which fescue toxicosis affects the bovine reproductive tract have yet to be discovered. The objective of this study was to determine if the onset of fescue toxicosis conditions would alter the blood perfusion observed in the CL and peripheral concentrations of progesterone in cattle. We hypothesized that during fescue toxicosis, the vasoconstrictive symptoms would lead to a reduction in CL blood perfusion thus decreasing peripheral concentrations of progesterone. Overall, fescue toxicosis was induced as cows fed an E+ treatment diet had greater rectal temperatures and reduced pulse pressure and mean arterial pressure measurements; however, total blood perfusion of the CL and peripheral concentrations of progesterone did not differ in cattle under fescue toxicosis compared to those without.

Fescue toxicosis is a condition that afflicts livestock grazing endophyte-infected tall fescue and is particularly detrimental to pregnant mares. A two year evaluation study of a novel endophtye-infected cultivar, AGRFA-144 (A-144), did not induce fescue toxicosis in late-term pregnant mares. All mares delivered viable foals except in E+ group which had two viable foals, one stillborn-dystocia and one compromised foal which was euthanized at 72 h pp. Serum P4 concentrations were similar among A-144, NE+, and E- mares (p>0.05). Foal BW and foal/placental weight ratios were similar for A-144, NE+, and E- (p>0.05). Foal serum P4 was similar on 1 d and 2 d in all groups, but was lower (p = 0.049) in the A-144 group than the E- foals on day 0. Neutrophil/lymphocyte ratios were similar (~5:1) in all foals on d 0 and 2. IgG values were similar (p>0.05) among A-144, NE+, and E-.

Sixty steers were grazed on toxic tall fescue for 104 days to determine the effects of hair coats and steroidal ear implants on physiological measurements. Steers were stratified by body weight and hair coat color for assignment to six, 3.0-ha pastures of 'Kentucky 31' tall fescue. Main plot treatments of either ten clipped or ten unclipped steers were randomly assigned to pastures. Five steers in each pasture were implanted with Synovex-S (200 mg progesterone-20 mg estradiol) and five were implanted with Compudose (25 mg estradiol) as sub-plot treatments. Hair growth rate averaged 0.29 mm/day. Sweating rate declined (P andlt; 0.001) over the grazing period and was higher (Pandlt; 0.10) with the estradiol implant. Rectal temperatures were lower (P andlt; 0.05) in clipped cattle (39.3 vs. 39.5??C) when the highest ambient temperature (33??C) of the study was recorded. At high environmental temperatures, percentage of steers actively grazing was negatively correlated (P andlt; 0.10) with ambient temperature. Winter hair coat retention, continuous hair growth, and reduced sweating caused impaired thermoregulation and thus decreased grazing frequency resulting in poor animal performance.

The present investigation was designed to investigate the use of blessed thistle (Cnicus benedictus) in amelioration of fescue toxicosis in beef cattle. Twenty-seven crossbred Angus cows were blocked by age and weight into groups of three. Each group (n=9) was then randomly assigned to one of three dietary treatments: endophyte-free (EF), endophyte-infected (EI), or endophyte-infected with addition of cut and stemmed blessed thistle (EIBT). Each group was also randomly assigned to one of three 29-day replicates. Parameters measured during this trial included: urinary ergot alkaloid concentration (ng ergot alkaloids/mg creatinine), body weight (kg), rectal temperature (°C), serum progesterone (ng/ml), and serum prolactin (ng/ml). No effect of treatment (P>0.05) was detected in any of these parameters. A treatment x time interaction (P<0.0001) was observed for progesterone concentrations, likely a result of estrous cyclicity of cows. Results of this study suggest that we were unsuccessful in inducing fescue toxicity in test subjects assigned to EI and EIBT treatments. Minimal dietary ergovaline (1.72 μg kg-1) and cool ambient temperatures (-6.7°C to 23.3°C) likely contributed to this inability. Data from this research do suggest, however, that C. benedictus can be successfully incorporated into cattle diets. Further research will need to be performed to fully elucidate what, if any, benefits blessed thistle can have in the treatment of fescue toxicity.

Endophyte infected Tall fescue (Festuca arundinacea Schreb.) is the most dominant grass used for pasture in the Southeastern U.S. As a result, fescue toxicosis is a major concern. Producers need alternative forages for grazing cattle that do not have this negative aspect. The objective of this experiment was to determine the grazing behavior of cattle grazing Lakota (L) prairie grass (Bromus catharticus Vahl.), endophyte infected (E+), endophyte free (E-), and novel endophyte (Q) tall fescues. Angus-crossbred steers (279±8 kg) steers wore electronic behavior data recorders in four sampling periods, and direct visual appraisals of behavior were taken in five sampling periods during the months of May to September, 2004. Overall, during the visual appraisal phase steers grazing L spent most time (P<0.05) grazing while E+ spent the least time grazing. Overall, steers grazing E+ spent more time (P<0.05) idling than those on L, E-, or Q. Steers grazing E+ spent more time (P<0.05) standing than steers grazing Q. Steers grazing Q and E- spent more time (P<0.05) lying than those grazing E+. During the data recorder phase there were no significant differences between treatments for time spent grazing. Steers grazing E+ spent less time (P<0.05) lying and ruminating than steers grazing Q or L. Conversely, time spent standing and idling for steers grazing E+ was higher (P<0.05) than for steers grazing Q or L. These results indicate that L, E-, and Q may offer benefits to producers due to more time spent in productive activities during summer months. / Master of Science

Tall fescue (Lolium arundinaceum) is the principal cool-season species within pastures of the southeastern USA and is known to have a mutualistic relationship with a fungal endophyte (Neotyphodium coenophialum) that produces the ergot alkaloids responsible for tall fescue toxicosis. Management of the reproductive growth of tall fescue is necessary, as the seedheads contain the highest concentrations of ergot alkaloids, and livestock have been documented to selectively graze these tissues. Recently, the herbicide Chaparral™ has been shown to be an effective method to prevent seedhead production in tall fescue pastures while also increasing steer gains at a low stocking rate. The objective of this study was to compare the impact of Chaparral on steer and pasture production under multiple grazing intensities (GI). Chaparral (0 and 140 g ha-1) and two levels of GI (low: 3300±250 kg ha-1 & moderate: 2500±250 kg ha-1) treatments were arranged in a factorial combination as RCBD with three replications. Tall fescue seedhead densities were decreased (P < 0.05) within the Chaparral-treated pastures, but efficiency of the inhibition varied slightly between growing seasons. Chaparral-treated pastures had lower (P < 0.05) forage availabilities and contained forage with higher (P < 0.05) concentrations of crude protein (CP) and in vitro digestible dry matter (IVDDM) during both growing season. Steers within the Chaparral-treated pastures and low GI treatment had higher average daily gains (ADG). Carrying capacities (CC) were lowest and highest within the Chaparral-low GI and control-moderate GI treatments, respectively. Estimates of CC were not different (P > 0.15) between the Chaparral-moderate GI and control-low GI treatments. The higher ADG compensated for the lower CC of the Chaparral and low GI treatments and resulted in no difference (P > 0.60) in total gain per hectare (GPH) between grazing intensities and herbicide treatments in 2011. In 2012, the GPH were higher within the control and moderate GI treatments due to a lessening in the magnitude of difference between the herbicide and GI treatments. The effects of these treatments for alleviating symptoms of tall fescue toxicosis were inconclusive due to the low levels of ergot alkaloids production.