Location: Forage-animal Production ResearchTitle: Dietary exposure to ergot alkaloids decreases contractility of bovine mesenteric vasculature Author
Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2013
Publication Date: 7/8/2013
Citation: Egert, A.M., Kim, D., Harmon, D.L., Klotz, J.L. 2013. Dietary exposure to ergot alkaloids decreases contractility of bovine mesenteric vasculature. J. Anim. Sci. Vol. 91, E-Suppl. 2:214. Interpretive Summary:
Technical Abstract: Ergot alkaloids are hypothesized to cause vasoconstriction in the midgut, and prior exposure may affect vasoactivity of these compounds. Objectives were to profile vasoactivity of ergot alkaloids in mesenteric artery and vein and determine if previous exposure to endophyte-infected tall fescue affected vasoactivity of ergonovine (ERN), ergocryptine (ERP), ergotamine (ERT), ergocristine (ERS), ergocornine (ERO), ergovaline (EXT), lysergic acid (LSA), and 5-hydroxytryptamine (5HT). Ruminally cannulated Angus steers (n=12; BW=547±31 kg) were paired by weight and randomly assigned to 6 blocks. Steers were ruminally dosed daily with 1 kg of either endophyte-infected (E+; 4.45 ppm ergovaline) or endophyte-free (E-) tall fescue seed for 21 d prior to slaughter. Branches of mesenteric artery (MA) and vein (MV) supporting the distal jejunum were collected after slaughter, placed in a modified Krebs-Henseleit buffer on ice, cleaned of fat and connective tissue, and sectioned into 2 mm segments. Vessels were equilibrated to 1.0 g tension for 90 min in a multi-myograph chamber with 5 mL of Krebs-Henseleit buffer and constant oxygenation (95 %O2/5% CO2; pH=7.4; 37°C). Final working concentrations of alkaloids ranged from 1x10-6 to 5x10-10 M for EXT and 1x10-4 to 5x10-9 M for all other agonists. Contractile response was normalized to a maximum KCl response. Data were analyzed using PROC MIXED of SAS for effects of seed treatment, agonist concentration, and the interaction. There were seed x concentration interactions (P<0.01) for ERP, ERT, ERS, ERO, EXT, ERN, and 5HT in MA indicating that E- steers had a greater contractile response than E+ steers. Steers receiving E- had a greater MV contractile response to ERP, ERN, and 5HT (P<0.01) and tended to for EXT (P=0.09). No response was evident for ERN, ERP, ERS, LSA, and 5HT in MA and ERN, LSA, and 5HT in MV of E+ steers. These data show that steers exposed to E+ had diminished contractility in small intestine vasculature and suggests initial exposure to ergot alkaloids has potential to alter nutrient absorption from the midgut, but the response may be transient.