Ergot alkaloids reduce circulating serotonin in the bovine

High deoxynivalenol and ergot alkaloid levels in wheat grain: effects on growth performance, carcass traits, rumen fermentation, and blood parameters of feedlot cattle

This study was designed to assess the impacts of a mixture of deoxynivalenol (DON) and ergot alkaloids (EAs) on growth performance, rumen function, blood parameters, and carcass traits of feedlot cattle. Forty steers (450 ± 6.0 kg) were stratified by weight and randomly allocated to 1 of 4 treatments; control-low (CON-L), control-high (CON-H) which contained low or high wheat screenings that lacked mycotoxins at the same level as the mycotoxin-low (MYC-L; 5.0 mg/kg DON, 2.1 mg/kg EA), and mycotoxin-high (MYC-H: 10 mg/kg DON, 4.2 mg/kg EA) diets that included wheat screening with mycotoxins. Steers were housed in individual pens for a 112-day finishing trial. Intake was 24.8% lower (P < 0.001) for MYC steers compared to CON steers. As a result, average daily gains of MYC steers were 42.1% lower (P < 0.001) than CON steers. Gain to feed ratio was also lower (P < 0.001) for MYC steers compared to CON steers. Platelets, alanine aminotransferase, globulins, and blood urea nitrogen were lower (P ≤ 0.008), and lymphocytes, glutathione peroxidase activity (GPx), and interleukin-10 (IL-10) were elevated (P ≤ 0.002) in MYC steers compared to CON steers. Hot carcass weights and backfat thickness were reduced (P < 0.001) in MYC steers, resulting in leaner (P < 0.001) carcasses and higher (P < 0.007) meat yield compared to CON steers. Results suggest that a mixture of DON and EAs negatively impacted health, performance, and carcass traits of feedlot steers, with the majority of this response likely attributable to EAs. However, more research is needed to distinguish the relative contribution of each mycotoxin to the specific responses observed.

The C-8-S-isomers of ergot alkaloids - a review of biological and analytical aspects

Ergot alkaloids are secondary metabolites that are produced by fungi and contaminate cereal crops and grasses. The ergot alkaloids produced by Claviceps purpurea are the most abundant worldwide. The metabolites exist in two configurations, the C-8-R-isomer (R-epimer) and the C-8-S-isomer (S-epimer). These two configurations can interconvert to one another. Ergot alkaloids cause toxic effects after consumption of ergot-contaminated food and feed at various concentrations. For bioactivity reasons, the C-8-R-isomers have been studied to a greater extent than the C-8-S-isomer since the C-8-S-isomers were considered biologically inactive. However, recent studies suggest the contrary. Analytical assessment of ergot alkaloids now includes the C-8-S-isomers and high concentrations of specific C-8-S-isomers have been identified. The inclusion of the C-8-S-isomer in regulatory standards is reviewed. This review has identified that further research into the C-8-S-isomers of ergot alkaloids is warranted. In addition, the inclusion of the C-8-S-isomers into regulatory recommendations worldwide for food and feed should be implemented. The objectives of this review are to provide an overview of historic and current studies that have assessed the C-8-S-isomers. Specifically, this review will compare the C-8-R-isomers to the C-8-S-isomers with an emphasis on the biological activity and analytical assessment.

5-hydroxytryphophan mitigates ergot alkaloid-induced suppression of serotonin and feed intake in cattle

The impact of ergot toxicosis on livestock industries is detrimental and treatments are needed in many countries. The objective of this study was to evaluate the effects of acute exposure to ergot alkaloids and 5-hydroxytryptophan (5-HTP) supplementation on feed intake, serotonin metabolism, and blood metabolites in cattle. Eight Holstein steers (538 ± 18 kg) fitted with ruminal cannulas were used in a replicated 4 × 4 Latin Square design experiment with a 2 × 2 factorial treatment structure. The treatments were the combination of 0 (E-) or 15 µg ergovaline/kg BW (E+) and 0 (5HTP-) or 0.5 mg of 5-hydroxy-l-tryptophan/kg BW (5HTP+) administered daily for 6 d. Toxic endophyte-infected tall fescue seed was used to supply the daily dose of ergovaline. Endophyte-free seed was used to equalize seed intake between treatments. Ground seed was placed into the rumen immediately before feeding. The 5-HTP was dissolved in water and infused into the abomasum via the reticulo-omasal orifice. Blood was collected from a jugular vein catheter at 0, 1, 2, 4, 8, and 24 h after treatment administration. Ergovaline without 5-HTP (E+/5HTP-) decreased dry matter intake (DMI) in comparison to steers without ergovaline and 5-HTP (E-/5HTP-). However, 5-HTP infusion in association with ergovaline (E+/5HTP+) normalized the DMI. Although E + did not affect (P > 0.05) the area under the curve (AUC) of serum 5-HTP, 5-hydroxyindoleacetic acid, tryptophan, and kynurenine, serum and plasma serotonin concentrations were decreased (P < 0.05). The infusion of 5-HTP increased (P < 0.05) the AUC of serum 5-HTP, serum and plasma serotonin, and serum 5-hydroxyindoleacetic acid. In conclusion, acute exposure to ergot alkaloids reduced DMI and circulating serotonin in cattle but 5-HTP administration showed potential to normalize both circulating serotonin and feed intake.

Duration of ergovaline exposure influences serotonin-mediated vasoactivity of bovine mesenteric vasculature

Ergovaline (ERV), produced in toxic endophyte-infected tall fescue, causes potent vasoconstriction of bovine peripheral and visceral vasculature. Ergovaline acts as both an agonist and an antagonist in bovine gut blood vessels through serotonin (5-HT) receptors and it appears that the type of action could be influenced by the extent of ERV exposure. Because it was unclear how the duration of ERV exposure influences 5-HT-mediated vasoactivity, experiments were designed to evaluate how simultaneous or prior ERV exposure influenced 5-HT-mediated vasoactivity of mesenteric artery (MA) and vein (MV) segments from Holstein steers (N = 10). Vessels were incubated in Krebs-Henseleit buffer containing 0, 0.01, or 0.1 μM ERV for 24 h prior to the 5-HT dose-response or exposed to fixed concentrations of 0, 0.01, or 0.1 μM ERV simultaneously during the 5-HT dose-response. Vessels were suspended in chambers of a multimyograph containing Krebs-Henseleit buffer and equilibrated to 1 g tension for 90 min. Vessels were exposed to increasing concentrations of 5-HT (5 × 10-8 M to 1 × 10-4 M) every 15 min and contractile responses were normalized as a percentage of the maximum contractile response induced by 120 mM KCl reference addition. Two-way analysis of variance was used to separately analyze data for each vessel type and duration of exposure using the MIXED procedure of SAS. When 5-HT concentration increased from 5 × 10-8 to 1 × 10-6 M, simultaneous addition of 0.1 μM ERV increased (P < 0.01) the contractile response of MV compared with additions of 0 and 0.01 μM ERV. At 1 × 10-4 M 5-HT, the simultaneous presence of 0.01 and 0.1 μM ERV decreased (P < 0.01) the contractile response of both MA and MV compared with 0 μM ERV addition. As 5-HT concentrations increased, the contractile response increased (P < 0.01) in both MA and MV with no previous ERV exposure, but decreased in MA and MV with 24 h prior exposure to 0.01 and 0.1 μM ERV. These data demonstrate that the duration of ERV exposure influences 5-HT-mediated vasoconstriction and likely vasorelaxation in bovine mesenteric vasculature. If ERV and 5-HT exposure occur simultaneously, ERV can act as a partial agonist of 5-HT-mediated vasoconstriction. If 5-HT exposure occurs after blood vessels have had prior ERV exposure, it appears that 5-HT may induce vasorelaxation of blood vessels. More research is needed to identify cellular and molecular mechanisms involved with 5-HT-mediated vasoactivity.

Influence of Prolonged Serotonin and Ergovaline Pre-Exposure on Vasoconstriction Ex Vivo

Ergot alkaloid mycotoxins interfere in many functions associated with serotonergic neurotransmitters. Therefore, the objective was to evaluate whether the association of serotonin (5-hydroxytryptamine, 5-HT) and ergot alkaloids during a 24 h pre-incubation could affect the vascular contractile response to ergot alkaloids. To evaluate the effects of 24 h exposure to 5-HT and ergot alkaloids (ergovaline, ERV), two assays were conducted. The first assay determined the half-maximal inhibitory concentration (IC₅₀) following the 24 h pre-exposure period, while the second assay evaluated the effect of IC₅₀ concentrations of 5-HT and ERV either individually or in combination. There was an interaction between previous exposure to 5-HT and ERV. Previous exposure to 5-HT at the IC₅₀ concentration of 7.57 × 10⁻⁷ M reduced the contractile response by more than 50% of control, while the exposure to ERV at IC₅₀ dose of 1.57 × 10⁻¹⁰ M tended to decrease (p = 0.081) vessel contractility with a response higher than 50% of control. The 24 h previous exposure to both 5-HT and ERV did not potentiate the inhibitory response of blood vessels in comparison with incubation with each compound alone. These results suggest receptor competition between 5-HT and ERV. More studies are necessary to determine the potential of 5-HT to treat toxicosis caused by ergot alkaloids.