Comparative efficacy of tannin-free grain sorghum varieties for the control of necrotic enteritis caused by Clostridium perfringens in broiler chickens.

A 28-day battery cage study was conducted to test the efficacy of tannin-free grain sorghum varieties fed to Cobb 500 male broiler chickens (n = 512) and challenged with Eimeria maxima (EM) and Clostridium perfringens (CP). Birds were fed 1 of 8 treatments (corn, red/bronze, white/tan, or U.S. No. 2 sorghum) and were grouped by challenge method (challenged with EM/CP or unchallenged). On d 14, birds in the challenge group were orally inoculated with ∼5,000 oocysts of EM, and on d 19, 20, and 21, birds were given a broth culture of CP with ∼108 CFU/mL once daily. On d 21, three birds were scored for the degree/presence of necrotic enteritis (NE) lesions. Birds and feed were group weighed (d 0, 14, 21, and 28) to calculate average feed intake (FI), body weight gain (BWG), and adjusted feed conversion ratio (AdjFCR). Intestinal integrity was assessed through histological analysis of intestinal tissues, and change in transcriptome was determined using mRNA-sequencing on intestinal mucosa. Relative concentrations of secondary metabolites in grain sorghum were determined by LC-MS/MS analysis. Data were analyzed as a 2-way ANOVA with factors of treatment, challenge and their interaction. Regardless of challenge from 14 to 21 d, birds on the corn, white/tan, and U.S. No. 2 treatments were more efficient than those fed red/bronze treatment (P = 0.0026). From 14 to 28 d, BWG was significantly higher for the white/tan treatment (P = 0.024) compared to the red/bronze treatment. At 21 d, a significant interaction was observed for lesion score (P = 0.0001) in which, challenged birds fed red/bronze and white/tan treatments had reduced intestinal lesions compared to U.S. No. 2 and corn treatments. No differences among treatments were observed in jejunum morphology, but differential expression analysis showed an upregulation in defense response to bacteria and biotic stress in the challenged red/bronze treatment compared to the challenged corn. This study demonstrated improved gut health and minimal impact on growth and efficiency of broilers fed select grain sorghum varieties when challenged with EM/CP.

Influence of work organization and work environment on missed work, productivity, and use of pain medications among construction apprentices.

BACKGROUND: Construction is among the most dangerous industries. In addition to traditional hazards for workplace injury and illness, other threats to health and well-being may occur from work organization and work environment factors, including irregular employment, long commutes, long work hours, and employer policies regarding health and safety. These nontraditional hazards may affect work and health outcomes directly, or through effects on health behaviors. The cumulative impacts of both traditional and nontraditional hazards on health-related outcomes among construction workers are largely unknown. METHODS: We conducted a survey among apprentice construction workers to identify relationships between work organization and environmental factors with five outcomes of economic relevance to employers: missed work due to work-related injury, missed work due to any pain or injury, self-reported workability, health-related productivity, and use of prescription medications for pain. RESULTS: A total of 963 surveys were completed (response rate 90%) in this young (mean age 28) working cohort. Multivariate Poisson regression models found associations between the outcomes of interest and multiple work factors, including job strain, safety behaviors of coworkers, and mandatory overtime. Univariate analysis showed additional associations, including precarious work, and supervisor support for safety. CONCLUSIONS: Findings from this cross-sectional study suggest that work organization and environment factors influence health and work outcomes among young construction trade workers. Future work with longitudinal data will examine the hypothesized paths between work factors, health behaviors, health outcomes, and work outcomes.

Development of targeted messages to promote smoking cessation among construction trade workers.

Blue-collar workers, particularly those in the construction trades, are more likely to smoke and have less success in quitting when compared with white-collar workers. Little is known about health communication strategies that might influence this priority population. This article describes our formative work to develop targeted messages to increase participation in an existing smoking cessation program among construction workers. Using an iterative and sequential mixed-methods approach, we explored the culture, health attitudes and smoking behaviors of unionized construction workers. We used focus group and survey data to inform message development, and applied audience segmentation methods to identify potential subgroups. Among 144 current smokers, 65% reported wanting to quit smoking in the next 6 months and only 15% had heard of a union-sponsored smoking cessation program, despite widespread advertising. We tested 12 message concepts and 26 images with the target audience to evaluate perceived relevance and effectiveness. Participants responded most favorably to messages and images that emphasized family and work, although responses varied by audience segments based on age and parental status. This study is an important step towards integrating the culture of a high-risk group into targeted messages to increase participation in smoking cessation activities.

Postgraze assessment of toxicosis symptoms for steers grazed on toxic endophyte-infected tall fescue pasture.

A 2-yr pen experiment was conducted using 12 different crossbred Angus steers each year to determine if short-term changes in prolactin concentrations, body temperature, and vasoconstriction reflect recovery from fescue toxicosis after steers that previously grazed toxic endophyte (Neotyphodium coenophialum)-infected Kentucky 31 tall fescue [Lolium arundinaceum (Schreb.) Darbysh] are placed on nontoxic feed. Groups of 6 steers from toxic endophyte-infected and endophyte-free tall fescue grazing treatments were blocked by BW for assignment to pens as a randomized complete block design with 2 replications. Two environments were implemented by initiating the experiment on 18 August in yr 1 and on 8 September in yr 2 for durations of 30 and 21 d, respectively. Rectal temperatures were recorded, jugular blood was collected for assaying serum prolactin, and cross sections of the caudal artery were ultrasonically imaged at selected time points to evaluate temporal changes in the response variables. Rectal temperatures in steers on the toxic endophyte pasture treatment declined (P < 0.05) linearly over time in yr 1 and 2 and were similar (P > 0.10) to those on endophyte-free treatment on d 30 in yr 1 and by d 15 in yr 2. Prolactin concentrations in steers on the toxic endophyte pasture treatment showed curvilinear increases (P < 0.05) over time and were similar (P > 0.10) to steers on the endophyte-free treatment by d 15 in yr 1 and by d 10 in yr 2. Luminal areas of the caudal artery in toxic endophyte steers were less (P < 0.05) than those in endophyte-free steers across all dates in both years. Results indicated that rectal temperatures in steers after they are removed from toxic fescue may decrease over time, but temporal changes in rectal temperatures could be affected more by prevailing ambient temperatures than by actual mitigation of fescue toxicosis. Prolactin concentrations in steers after they are removed from toxic endophyte tall fescue can increase and stabilize in less than 2 wk, but alkaloid-induced vasoconstriction that causes a vulnerability to severe heat stress is not alleviated within 30 d.

Antagonism of lateral saphenous vein serotonin receptors from steers grazing endophyte-free, wild-type, or novel endophyte-infected tall fescue.

Pharmacologic profiling of serotonin (5HT) receptors of bovine lateral saphenous vein has shown that cattle grazing endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) have altered responses to ergovaline, 5HT, 5HT2A, and 5HT7 agonists. To determine if 5HT receptor activity of tall fescue alkaloids is affected by grazing endophyte-free (EF), wild-type [Kentucky-31 (KY31)], novel endophyte AR542-infected (MAXQ), or novel endophyte AR584-infected (AR584) tall fescue, contractile responses of lateral saphenous veins biopsied from cattle grazing these different fescue-endophyte combinations were evaluated in presence or absence of antagonists for 5HT2A (ketanserin) or 5HT7 (SB-269970) receptors. Biopsies were conducted over 2 yr on 35 mixed-breed steers (361.5 ± 6.3 kg) grazing EF (n = 12), KY31 (n = 12), MAXQ (n = 6), or AR584 (n = 5) pasture treatments (3 ha) between 84 and 98 d (Yr 1) or 108 to 124 d (Yr 2). Segments (2 to 3 cm) of vein were surgically biopsied, sliced into 2- to 3-mm cross-sections, and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O2/5% CO2; pH = 7.4; 37°C). Veins were exposed to increasing concentrations of 5HT, ergovaline, and ergovaline + 1 × 10(-5) M ketanserin or + 1 × 10(-6) M SB-269970 in Yr 1. In Yr 2, ergotamine and ergocornine were evaluated in presence or absence of 1 × 10(-5) M ketanserin. Contractile response data were normalized to a reference addition of 1 × 10(-4) M norepinephrine. In Yr 1, contractile response to 5HT and ergovaline were least (P < 0.05) in KY31 pastures and the presence of ketanserin greatly reduced (P < 0.05) the response to ergovaline in all pastures. However, presence of SB-269970 did not (P = 0.91) alter contractile response to ergovaline. In Yr 2, there was no difference in contractile response to ergotamine (P = 0.13) or ergocornine (P = 0.99) across pasture treatments, but ketanserin reduced (P < 0.05) the contractile response to both alkaloids. The 5HT2A receptor is involved in alkaloid-induced vascular contraction and alkaloid binding may be affected by exposure to different endophyte-fescue combinations.

Forages and pastures symposium: managing the tall fescue-fungal endophyte symbiosis for optimum forage-animal production.

Alkaloids produced by the fungal endophyte (Neotyphodium coenophialum) that infects tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] are a paradox to cattle production. Although certain alkaloids impart tall fescue with tolerances to environmental stresses, such as moisture, heat, and herbivory, ergot alkaloids produced by the endophyte can induce fescue toxicosis, a malady that adversely affects animal production and physiology. Hardiness and persistence of tall fescue under limited management can be attributed to the endophyte, but the trade-off is reduced cattle production from consumption of ergot alkaloids produced by the endophyte. Improved understanding and knowledge of this endophyte-grass complex has facilitated development of technologies and management systems that can either mitigate or completely alleviate fescue toxicosis. This review discusses the research results that have led to development of 5 management approaches to either reduce the severity of fescue toxicosis or alleviate it altogether. Three approaches manipulate the endophyte-tall fescue complex to reduce or alleviate ergot alkaloids: 1) use of heavy grazing intensities, 2) replacing the toxic endophyte with nonergot alkaloid-producing endophytes, and 3) chemical suppression of seed head emergence. The remaining 2 management options do not affect ergot alkaloid concentrations in fescue tissues but are used 1) to avoid grazing of tall fescue with increased ergot alkaloid concentrations in the late spring and summer by moving cattle to warm-season grass pasture and 2) to dilute dietary alkaloids by interseeding clovers or feeding supplements.

Alterations in serotonin receptor-induced contractility of bovine lateral saphenous vein in cattle grazing endophyte-infected tall fescue.

As part of a 2-yr study documenting the physiologic impact of grazing endophyte-infected tall fescue on growing cattle, 2 experiments were conducted to characterize and evaluate effects of grazing 2 levels of toxic endophyte-infected tall fescue pastures on vascular contractility and serotonin receptors. Experiment 1 examined vasoconstrictive activities of 5-hydroxytryptamine (5HT), α-methylserotonin (ME5HT; a 5HT(2) receptor agonist), d-lysergic acid (LSA), and ergovaline (ERV) on lateral saphenous veins collected from steers immediately removed from a high-endophyte-infected tall fescue pasture (HE) or a low-endophyte-infected mixed-grass (LE) pasture. Using the same pastures, Exp. 2 evaluated effects of grazing 2 levels of toxic endophyte-infected tall fescue on vasoconstrictive activities of (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), BW 723C86 (BW7), CGS-12066A (CGS), and 5-carboxamidotryptamine hemiethanolate maleate (5CT), agonists for 5HT(2A),( 2B), 5HT(1B), and 5HT(7) receptors, respectively. One-half of the steers in Exp. 2 were slaughtered immediately after removal from pasture, and the other one-half were fed finishing diets for >91 d before slaughter. For Exp. 1, maximal contractile intensities were greater (P < 0.05) for steers grazing LE pastures than HE pastures for 5HT (73.3 vs. 48.9 ± 2.1%), ME5HT (52.7 vs. 24.9 ± 1.5%), and ERV (65.7 vs. 49.1 ± 2.6%). Onset of contractile response did not differ for 5HT (P = 0.26) and ERV (P = 0.93), but onset of ME5HT contraction was not initiated (P < 0.05) in HE steers until 10(-4) compared with 10(-5) M in LE-grazing steers. For Exp. 2, maximal contractile intensities achieved with DOI were 35% less (P < 0.05), whereas those achieved with 5CT were 37% greater (P < 0.05), in steers grazing HE pastures. Contractile response to CGS did not differ between pasture groups, and there was an absence of contractile response to BW7 in both groups. There were no differences between endophyte content in contractile responses after animals were finished for >91 d. Experiment 1 demonstrated that grazing of HE pastures for 89 to 105 d induces functional alterations in blood vessels, as evidenced by reduced contractile capacity and altered serotonergic receptor activity. Experiment 2 demonstrated that grazing HE pastures alters vascular responses, which may be mediated through altered serotonin receptor activities, and these alterations may be ameliorated by the removal of ergot alkaloid exposure as demonstrated by the absence of differences in finished steers.

Constriction of bovine vasculature caused by endophyte-infected tall fescue seed extract is similar to pure ergovaline.

Ergovaline has been extensively used to study vasoactive effects of endophyte- (Neotyphodium coenophialum) infected tall fescue (Lolium arundinaceum). However, initial results indicated that an extract of toxic tall fescue seed (E+EXT) is more potent than ergovaline alone in a right ruminal artery and vein bioassay. The E+EXT induced a greater contractile response than an equal concentration of ergovaline alone in the ruminal artery of heifers (P = 0.018). This led to a hypothesis that other compounds in the seed extract contribute to vasoconstriction. Thus, experiments were conducted to determine if vasoactivity of an E+EXT is different from a mixture of ergot alkaloids (ALK; ergovaline, ergotamine, ergocristine, ergocryptine, ergocornine, ergonovine, and lysergic acid) of similar concentrations and to determine if the vasoactivity of an E+EXT differs from an endophyte-free tall fescue seed extract (E-EXT). Segments of lateral saphenous vein and right ruminal artery and vein were collected from Holstein steers (n = 6) shortly after slaughter. Vessels were cleaned of excess connective tissue and fat and sliced into segments that were suspended in a multimyograph chamber with 5 mL of continually oxygenated Krebs-Henseleit buffer, equilibrated for 90 min, and exposed to a reference compound (120 mM KCl for ruminal vessels and 0.1 mM norepinephrine for saphenous vein). Increasing concentrations of each treatment (E+EXT, E-EXT, ALK, and ergovaline) were added to the respective chamber every 15 min after buffer replacement. Data were normalized as a percentage of maximal contractile response of the reference compound and fit to a sigmoidal concentration response curve. Ergovaline, ALK, and E+EXT induced similar responses in the saphenous vein, ruminal artery, and ruminal vein. The E+EXT displayed a smaller EC(50) (half maximal effective concentration) than ergovaline or ALK in the saphenous vein and ruminal vein (P < 0.008), but not the ruminal artery (P = 0.31). Extrapolated maximum response was greatest in the saphenous vein for ergovaline, least for E+EXT, and intermediate for ALK (P < 0.0001). The E-EXT did not induce a contractile response in any vessel tested (P > 0.1). Data from this study indicate that ergovaline is largely responsible for the locally induced vasoconstriction of bovine vasculature observed with endophyte-infected tall fescue.

Bovine neuronal vesicular glutamate transporter activity is inhibited by ergovaline and other ergopeptines.

l-Glutamate (Glu) is a major excitatory neurotransmitter responsible for neurotransmission in the vertebrate central nervous system. Vesicular Glu transporters VGLUT1 and VGLUT2 concentrate (50mM) Glu [Michaelis constant (measuring affinity), or K(m),=1 to 4mM] into synaptic vesicles (SV) for subsequent release into the synaptic cleft of glutamatergic neurons. Vesicular Glu transporter activity is dependent on vacuolar H(+)-ATPase function. Previous research has shown that ergopeptines contained in endophyte-infected tall fescue interact with dopaminergic and serotoninergic receptors, thereby affecting physiology regulated by these neuron types. To test the hypothesis that ergopeptine alkaloids inhibit VGLUT activity of bovine cerebral SV, SV were isolated from cerebral tissue of Angus-cross steers that were naive to ergot alkaloids. Immunoblot analysis validated the enrichment of VGLUT1, VGLUT2, synaptophysin 1, and vacuolar H(+)-ATPase in purified SV. Glutamate uptake assays demonstrated the dependence of SV VGLUT-like activity on the presence of ATP, H(+)-gradients, and H(+)-ATPase function. The effect of ergopeptines on VGLUT activity was evaluated by ANOVA. Inhibitory competition (IC(50)) experiments revealed that VGLUT-mediated Glu uptake (n=9) was inhibited by ergopeptine alkaloids: bromocriptine (2.83±0.59µM)

Board-invited review: St. Anthony's Fire in livestock: causes, mechanisms, and potential solutions.

After a brief history of ergot alkaloids and ergotism, this review focuses on the metabolism and mechanisms of action of the ergot alkaloids. The authors provide models of how these alkaloids afflict grazing livestock under complex animal-plant/endophyte-environmental interactions. Alkaloid chemistry is presented to orient the reader to the structure-function relationships that are known to exist. Where appropriate, the medical literature is used to aid interpretation of livestock research and to provide insight into potential modes of action and alkaloid metabolism where these are not known for livestock. In closing the paper, we discuss management of ergot alkaloid intoxication in livestock and future research needs for this field of study.

Effect of ergot alkaloids on contractility of bovine right ruminal artery and vein.

Ergot alkaloids produced by the endophyte (Neotyphodium coenophialum) associated with tall fescue (Lolium arundinaceum) are implicated in the clinical signs of fescue toxicosis. These compounds were hypothesized to correspondingly affect foregut vasculature. The objective of this study was to determine vasoconstrictive potentials of ergovaline, ergotamine, ergocryptine, ergocristine, ergonovine, ergocornine, and lysergic acid on right ruminal artery and vein. Segments of right ruminal artery and vein were collected from the ventral coronary groove of predominantly Angus heifers (n = 10) shortly after slaughter and placed in a modified Krebs-Henseleit buffer on ice. Vessels were cleaned of excess connective tissue and fat, sliced into 2- to 3-mm segments, and suspended in a multi-myograph chamber with 5 mL of continuously oxygenated Krebs-Henseleit buffer (95%O(2)/5% CO(2); pH 7.4; 37°C). Arteries and veins were equilibrated to 1.0 and 0.5 g, respectively, for 90 min followed by the reference addition of 120 mM KCl. Increasing concentrations of each alkaloid were added to the respective chamber every 15 min after buffer replacement. Data were normalized as a percentage of the contractile response induced by KCl. Alkaloid (P < 0.0001), concentration (P < 0.0001), and vessel type (artery or vein; P = 0.004) affected contractility. No arterial response was observed until 10(-6) M for ergovaline and ergotamine; 10(-5) M for ergocryptine, ergocornine, and ergonovine; and 10(-4) M for ergocristine. Lysergic acid did not induce a contractile response in the ruminal artery. No venous contractile response was observed until concentrations of 10(-6) M for ergovaline, 10(-5) M for ergotamine, and 10(-4) M for ergocryptine and ergocristine were achieved. Lysergic acid, ergonovine, and ergocornine did not induce a contractile response in the ruminal vein. A greater arterial maximal response was observed for ergovaline (P < 0.0001), whereas the arterial and venous responses were not different for ergotamine (P = 0.16), ergocryptine (P = 0.218), and ergocristine (P = 0.425). These results indicate that ergot alkaloids associated with toxic endophyte-infected tall fescue are vasoactive and can potentially alter arterial blood supply and venous drainage from the bovine foregut.

A vascular contractility bioassay using bovine right ruminal artery and vein.

Endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) produces ergot alkaloids that are associated with peripheral vasoconstriction in grazing animals, and ingestion of these alkaloids may affect splanchnic vasculature. Peripheral effects of ergot alkaloids have been well documented previously in cattle using a lateral saphenous vein bioassay. Because of significant differences in morphological and functional characteristics between vasculature supporting digestive and peripheral tissues, the bovine foregut vascular model required validation. Experiments were conducted, using dose-responses to norepinephrine and serotonin that were normalized to either 0.12 M KCl, or 0.1 mM norepinephrine or serotonin, to compare responses of vessels equilibrated at different tensions on the day of collection or the day after collection. Segments of a branch of right ruminal artery and vein were collected from the ventral coronary groove of healthy cattle of mixed breed, age, and sex (n = 20) at local abattoirs. Cross-sections of the artery and vein were suspended on luminal supports in a chamber of a multimyograph containing continuously oxygenated Krebs-Henseleit buffer (95% O(2)/5% CO(2), pH 7.4; 37°C). Vessels were allowed to equilibrate at either 0.5 or 1.0 g of tension for 1.5 h before exposure to a reference compound. Increasing concentrations of each biogenic amine were administered in 15-min intervals after buffer replacement. Data were normalized as a percentage of the contractile response induced by the reference compound for each tension and day of analysis. The ruminal artery and vein were both more responsive to KCl as a reference compound (P < 0.05) than to norepinephrine or serotonin and did not differ between days when normalized with KCl. Ruminal arteries had greater contractile responses (P < 0.05) when tension was set to 1.0 g, compared with 0.5 g, during equilibration. The ruminal vein response had a more stable maintenance of baseline tension in vessels equilibrated at 0.5 g of resting tension. Development of this bioassay allows separation of the effects tall fescue alkaloids exert on both the right ruminal artery and vein as representative vessels that service tissues functioning in nutrient absorption.

Contractile response of fescue-naive bovine lateral saphenous veins to increasing concentrations of tall fescue alkaloids.

Various alkaloids found in endophyte-infected tall fescue have been shown to elicit different effects in the grazing animal. As part of an ongoing characterization of vascular response generated by different alkaloids, the objective of this study was to examine the vasoconstrictive potentials of ergonovine (a simple lysergic acid derivative) and alpha-ergocryptine, ergocristine, and ergocornine (all ergopeptine alkaloids) using bovine lateral saphenous veins (cranial branch) biopsied from fescue-naïve cattle. Segments (2 to 3 cm) of vein were surgically biopsied from healthy crossbred yearling cattle (n = 18; 274 +/- 8 kg of BW). Veins were trimmed of excess fat and connective tissue, sliced into 2 to 3 mm sections, and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O(2)/5% CO(2); pH = 7.4; 37 degrees C). Tissue was allowed to equilibrate at 1 g of tension for 90 min before initiation of treatment additions. Increasing doses of each alkaloid (1 x 10(-10) to 1 x 10(-4) M) were administered every 15 min after buffer replacement. Data were normalized as a percentage of contractile response induced by a reference dose of norepinephrine (1 x 10(-4) M). Exposure of vein segments to increasing concentrations of ergocryptine, ergocristine, and ergonovine did not result in a contractile response until 1 x 10(-7) M, and ergocornine was even less potent (P < 0.05). Ergonovine had a greater maximal contractile intensity than ergocristine and ergocryptine (P < 0.05), with the 1 x 10(-4) M responses of ergonovine, ergocristine, ergocryptine, and ergocornine reaching maximums of 68.5 +/- 4.1, 45.5 +/- 4.5, 42.9 +/- 4.1%, and 57.2 +/- 9.9% of the norepinephrine maximum, respectively. The contractile response to increasing concentrations of ergonovine vs. ergocryptine, ergocristine, and ergocornine were opposite from previous evaluations of ergoline (e.g., lysergic acid) and ergopeptine (e.g., ergovaline) alkaloids using this bioassay, where the ergopeptine generated the greater contractile intensity. These data indicate that ergopeptines structurally different only at a single position of the peptide moiety do not exhibit differing contractile responses when considering contractile intensity. This difference may alter the potency when considering ergocornine was less potent than ergocryptine or ergocristine. These alkaloids may need to be considered when evaluating causative agents vasoconstriction associated with tall fescue-induced toxicosis.

Bioaccumulation of ergovaline in bovine lateral saphenous veins in vitro.

Ergot alkaloids have been associated with vasoconstriction in grazing livestock affected by the fescue toxicosis syndrome. Previous in vitro investigations studying how ergot alkaloids caused vasoconstriction have shown that ergovaline has a distinct receptor affinity and sustained contractile response. A similar contractile response has not been noted for lysergic acid. The objectives of this study were to determine if repetitive in vitro exposure of bovine lateral saphenous vein to lysergic acid or ergovaline would result in an increasing contractile response and if a measurable bioaccumulation of the alkaloids in the vascular tissue occurs over time. Segments of vein were surgically biopsied from healthy, Angus x Brangus cross-bred, fescue-naïve yearling heifers (n = 16) or collected from healthy mixed breed and sex cattle immediately after slaughter (n = 12) at a local abattoir. Veins were trimmed of excess fat and connective tissue, sliced into cross-sections, and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O(2)/5% CO(2); pH = 7.4; 37 degrees C). Contractile responses to repetitive additions of ergovaline (1 x 10(-9) and 1 x 10(-7) M) and lysergic acid (1 x 10(-5) and 1 x 10(-4) M) were evaluated using the biopsied veins. For the bioaccumulation experiments, veins collected at the abattoir underwent repetitive additions of 1 x 10(-7) M ergovaline and 1 x 10(-5) M lysergic acid and the segments were removed after every 2 additions and media rinses for alkaloid quantification via HPLC/mass spectrometry. Contractile data were normalized as a percentage of contractile response induced by a reference dose of norepinephrine (1 x 10(-4) M). Repetitive additions of 1 x 10(-9) M ergovaline and 1 x 10(-5) and 1 x 10(-4) M lysergic acid resulted in contractile response with a negative slope (P < 0.02). In contrast, repetitive addition of 1 x 10(-7) M ergovaline resulted in a contractile response that increased with each addition (P < 0.01). Lysergic acid and ergovaline were detected at all 4 exposure levels (2x to 8x), but only the 1 x 10(-7) M ergovaline treatment resulted in increased tissue content as the number of exposures increased (P < 0.05). These data indicate that ergovaline, but not lysergic acid, bioaccumulates with repetitive exposure in vitro. These results suggest that ergovaline may have a greater potential for inducing toxicosis in grazing animals than lysergic acid because of its potential to bioaccumulate at the cellular site of action.

Hemodynamics are altered in the caudal artery of beef heifers fed different ergot alkaloid concentrations.

Doppler ultrasonography was used to compare blood flow characteristics in the caudal artery of heifers fed diets with endophyte (Neotyphodium coenophialum) noninfected (E-, 0 microg of ergovaline/g of DM), a 1:1 mixture of endophyte-infected and E- (E+E-; 0.39 microg of ergovaline/g of DM), or endophyte-infected (E+, 0.79 microg of ergovaline/g of DM) tall fescue (Lolium arundinaceum) seed. Eighteen crossbred (Angus x Brangus) heifers [345 +/- 19 kg (SD)] were assigned to individual pens and fed chopped alfalfa hay plus a concentrate that contained E- tall fescue seed for 7 d during an adjustment period. A 9-d experimental period followed with feeding treatments of chopped alfalfa hay plus a concentrate with E+, E-, or E+E- seed being assigned randomly to pens. Doppler ultrasound measurements (caudal artery luminal area, peak systolic velocity, end diastolic velocity, mean velocity, heart rate, and flow rate) and serum prolactin were monitored during the adjustment (3 baseline measures) and during the experimental period (7 measures). Statistical analyses compared proportionate differences between baseline and responses at 3, 27, 51, 75, 171, and 195 h from initial feeding of the experimental diets. Serum prolactin concentrations for E+ and E+E- diets were less (P < 0.001) than baseline concentrations beginning at 27 and 51 h, respectively, from initial feeding of the diets. Although baseline measures were taken when ambient temperatures were likely below thermoneutrality, caudal artery luminal cross-sectional area in E+ heifers had declined (P = 0.004) from baseline by 27 h and remained less (P < 0.02) until 195 h, and caudal artery luminal area declined (P = 0.004) in E+E- heifers from baseline by 51 h and remained less (P < 0.07) until 171 h. Blood flow rate was slower than the baseline rate at 51 h for E+ (P = 0.058) and E+E- (P = 0.02 heifers, but blood flow remained slower in E+E- heifers for 48 h, whereas it remained slower in E+ heifers for 96 h. Adjustments in artery luminal area and blood rate with the 3 diets appeared to parallel the increases in ambient temperature. Heifers fed a diet containing a larger amount of ergot alkaloids had less of a response to ambient temperature than heifers consuming the diet with less or no ergot alkaloids.

Growing steers grazing high versus low endophyte (Neotyphodium coenophialum)-infected tall fescue have reduced serum enzymes, increased hepatic glucogenic enzymes, and reduced liver and carcass mass.

It is well established that grazing Neotyphodium coenophialum-infected forages results in reduced BW gain and serum prolactin concentrations of cattle. The objective of this study was to determine the potential effects of toxic endophyte-infected tall fescue consumption on blood metabolites, carcass characteristics, and content of proteins critical for AA metabolism in the liver, kidney, and LM tissue of growing steers. Steers grazed a low toxic endophyte (LE; 0.023 microg/g ergot alkaloids) tall fescue-mixed grass pasture (n = 9; BW = 266 +/- 10.9 kg; 5.7 ha) or a high toxic endophyte (HE; 0.746 microg/g of ergot alkaloids) tall fescue pasture (n = 10; BW = 267 +/- 14.5 kg; 5.7 ha) from June 14 through at least September 11 (> or =89 d). No difference was observed for BW (P < 0.10) for the overall 85-d growth period. Also, no differences were observed for ribeye area/100 kg of HCW (P > 0.91), backfat (P > 0.95), or backfat/100 kg of HCW (P > 0.67). However, ADG (P < 0.01), final BW (P < 0.05), HCW (P < 0.01), dressing percentage (P < 0.01), ribeye area (P < 0.01), whole liver wet weight (P < 0.01), and whole liver wet weight/100 kg of end BW (P < 0.01) were greater for LE steers than HE steers. After 85 d of grazing, serum concentrations of alkaline phosphatase (P < 0.05), alanine aminotransferase (P < 0.01), aspartate aminotransferase (P < 0.03), cholesterol (P < 0.01), lactate dehydrogenase (P < 0.01), and prolactin (P < 0.01) were less for HE than LE steers. At slaughter, hepatic content of cytosolic phosphoenolpyruvate carboxykinase (P < 0.01) was greater in HE steers than LE steers. Hepatic content of aspartate aminotransferase (P < 0.01) also was greater, whereas renal and LM content were not (P > or = 0.42). No differences (P > or = 0.15) were observed for hepatic, renal, and LM content of alanine aminotransferase, glutamate dehydrogenase, glutamine synthetase, and 3 glutamate transport proteins. These data indicate that the HE steers displayed classic endophyte toxicity symptoms for growth and blood variables, classic symptoms that were concomitant with novelly identified altered glucogenic capacity of the liver and decreases in carcass characteristics.

Technical note: Comparison between two tracing methods with ultrasonography to determine lumen area of the caudal artery in beef cattle.

Two experiments were conducted to compare variation between 2 tracing methods in measuring cross-sectional lumen area of the caudal artery in 5 beef heifers on 3 different dates (Exp. 1) and to compare tracing methods in detecting changes in artery lumen area after 5 heifers were switched from a diet containing nonendophyte-infected tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] seed to one containing endophyte-infected tall fescue seed (Exp. 2). Lumen area determined by tracing the Doppler flow signal was 25% less than that determined by tracing the intima of the connective tissue, but there was no difference (P = 0.90) in the variation of measures between the 2 methods in Exp. 1. Declines in lumen area were detected at the same level of significance (P < 0.01) for both tracing methods after cattle in Exp. 2 were switched from noninfected to infected tall fescue diets. Variation in lumen areas was different between noninfected and infected diets with tracing the Doppler flow signal (P < 0.05) or the intima of the connective tissue (P < 0.01). Results indicated that lumen area of the caudal artery can be measured with similar precision by tracing the intima of the connective tissue in the artery wall or the outer boundary of the Doppler flow signal.

Effects of selected combinations of tall fescue alkaloids on the vasoconstrictive capacity of fescue-naive bovine lateral saphenous veins.

Vasoconstriction is a response associated with consumption of toxic endophyte-infected tall fescue. It is not known if endophyte-produced alkaloids act alone or collectively in mediating the response. Therefore, the objective of this study was to examine the vasoconstrictive potentials of selected ergot alkaloids, individually or in paired combinations, using bovine lateral saphenous veins biopsied from fescue-naïve cattle. Segments (2 to 3 cm) of vein were surgically biopsied from healthy crossbred yearling heifers (n = 22; 330 +/- 8 kg of BW). Veins were trimmed of excess fat and connective tissue, sliced into 2- to 3-mm sections, and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O(2)/5% CO(2); pH = 7.4; 37 degrees C). Increasing doses of ergovaline, lysergic acid, and N-acetylloline individually or in combination were evaluated. Contractile data were normalized as a percentage of the contractile response induced by a reference dose of norepinephrine (1 x 10(- 4) M). Increasing concentrations of lysergic acid did not result in an appreciable contractile response until the addition of 1 x 10(- 4) M lysergic acid. In contrast, the vascular response to increasing concentrations of ergovaline was apparent at 1 x 10(- 8) M and increased to a maximum of 104.2 +/- 6.0% with the addition of 1 x 10(- 4) M ergovaline. The presence of N-acetylloline did not alter the onset or magnitude of vascular response to either lysergic acid or ergovaline. The presence of 1 x 10(- 5) M lysergic acid with increasing concentrations of N-acetylloline and ergovaline generated an increased contractile response during the initial additions compared with the responses of N-acetylloline and ergovaline alone. In the presence of 1 x 10(- 7) M ergovaline, the contractile response increased with increasing concentrations of N-acetylloline and lysergic acid. Neither N-acetylloline nor lysergic acid elicited an intense contractile response individually (maximum contractile responses of 1.9 +/- 0.3% and 22.6 +/- 4.1%, respectively), suggesting that this was the result of the repetitive addition of 1 x 10(- 7) M ergovaline. These data indicate that ergovaline is a more potent vascular toxicant than lysergic acid or N-acetylloline. The contractile responses of the ergovaline and lysergic acid combinations appeared to differ from the individual dose responses. These data support the possibility that an additive alkaloid exposure effect may exist and should be considered during evaluations of ergot alkaloids.

Ergovaline-induced vasoconstriction in an isolated bovine lateral saphenous vein bioassay.

Ergovaline has been proposed as a toxic component of endophyte-infected tall fescue. As many of the symptoms of fescue toxicosis are a result of compromised circulation, the objective of this study was to examine the vasoconstrictive potentials of ergovaline and a more documented ergopeptine, ergotamine, using a bovine, lateral (cranial branch) saphenous vein bioassay. Segments of the cranial branch of the lateral saphenous vein (2 to 3 cm) were collected from healthy, mixed breed cattle (n = 12 and n = 5 for the ergovaline and ergotamine experiments, respectively) at local abattoirs. The veins were trimmed of excess fat and connective tissue, sliced into 2- to 3-mm cross sections, and suspended in a myograph chamber containing 5 mL of a modified Krebs-Henseleit, oxygenated buffer (95% O2 + 5% CO2; pH = 7.4; 37 degrees C). The tissue was allowed to equilibrate at 1 g of tension for 90 min before of the addition of treatments. Increasing doses of ergovaline (1x10(-11) to 1 x10(-4) M) or ergotamine (1 x10(-11) to 1 x 10(-5) M) were administered every 15 min after buffer replacement. Contractile response data were normalized to a percentage induced by a reference dose of norepinephrine (1 x10(-4) M). Contractile responses of saphenous veins were similar for ergovaline and ergotamine. Initial contractile responses began at 1 x10(-8) M for both ergovaline and ergotamine (4.4 +/- 0.8% and 5.6 +/-1.1%, respectively). Vascular tension continued to increase as the alkaloid concentrations increased (maximums: 43.7 +/-7.1% at 1 x10(-5) M ergotamine; 69.6 +/- 5.3% at 1 x10(-4) M ergovaline). Interestingly, ergovaline-induced contractions (1 x10(-4) M) were not reversed by repeated buffer replacement over a 105-min period. As previously shown with ergotamine, these results confirm that ergovaline is a potent vasoconstrictor. The resistance of an ergovaline-induced contraction to relaxation over an extended period of time suggests a potential for bioaccumulation of this ergopeptine alkaloid and may aid in understanding its toxicity within the animal.