Ergot alkaloid exposure during gestation alters: III. Fetal growth, muscle fiber development, and miRNA transcriptome

Authors: GREENE, MASLYN - CLEMSON UNIVERSITY; BRITT, JESSI - CLEMSON UNIVERSITY; POWELL, R. REIGERS - CLEMSON UNIVERSITY; FELTUS, F. - CLEMSON UNIVERSITY; BRIDGES, JR., W. - CLEMSON UNIVERSITY; BRUCE, T. - CLEMSON UNIVERSITY; Klotz, James; MILLER, MARKUS - CLEMSON UNIVERSITY; DUCKETT, SUSAN - CLEMSON UNIVERSITY

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2019
Publication Date: 5/3/2019
Citation: Greene, M.A., Britt, J.L., Powell, R., Feltus, F.A., Bridges, Jr., W.C., Bruce, T., Klotz, J.L., Miller, M.F., Duckett, S.K. 2019. Ergot alkaloid exposure during gestation alters: III. Fetal growth, muscle fiber development, and miRNA transcriptome. Journal of Animal Science. https://doi.org/10.1093/jas/skz153.
DOI: https://doi.org/10.1093/jas/skz153

Interpretive Summary: The toxin ergovaline is produced by a fungal endophyte that lives symbiotically within tall fescue grass. Livestock consuming the grass also consume the toxin and can suffer from the syndrome fescue toxicosis. Pregnant ruminant livestock exposed to this toxin have newborns with reduced birthweights. The objective of this study was to evaluate how feeding tall fescue seed (ergovaline) alters fetal growth, muscle development and gene expression. This was done by feeding 36 pregnant ewes fungally infected or uninfected seed from d35 to d133 of gestation. Samples were collected on d133 when gestation was terminated. This study demonstrated that ewes receiving infected tall fescue seed during gestation, late in gestation in particular, produced smaller fetuses with lighter muscle and organ weights. Muscle fiber numbers were also reduced for these fetuses. Analysis of gene expression pathways demonstrated that cellular energy metabolism is altered from exposure to ergovaline during gestation potentially contributing to this change in growth. This study provides conclusive evidence on the negative impact that ergovaline exposure has on fetal development at animal, tissue, and molecular levels. Researchers focused on improving the understanding of how ergot alkaloids like ergovaline alter animal physiology will benefit directly from this work. This work also has long-term implications on eventual recommendations on management of pregnant ruminant livestock on tall fescue pasture as we are beginning to better understand the timing of the observed negative effects.

Technical Abstract: Tall fescue [Lolium arundinaceum (Schreb.) Darbysh] is the primary cool season forage grass in the Southeastern U.S. Most tall fescue contains an endophytic fungus (Epichloë coenophiala) that produces ergot alkaloids and upon ingestion induce fescue toxicosis. The objective of this study was to assess how exposure to ergot alkaloids during two stages of gestation alters fetal growth, muscle fiber formation and miRNA. Ewes (n =36; BW = 83.26 + 8.14 kg; 4/group; 9 groups) that were confirmed pregnant were randomly assigned to one of four treatments: E-/E-, E-/E+, E+/E-, or E+/E+ within group. Ewes were fed a total mixed ration containing endophyte-infected (E+) or endophyte-free (E-) fescue seed according to treatment assignment during MID (d 35 to 85) and LATE (d 86 to 133) with “/” denoting the switch in fescue treatment at d 85. Terminal surgeries were conducted on d 133 of gestation for collection of fetal data and muscle samples. Feeding E+ seed to ewes during LATE gestation, E-/E+ and E+/E+, reduced (P = 0.0079) fetal weight at d 133 of gestation by 599 g and 684 g, respectively, compared to fetuses from ewes fed E-/E- seed. Fetuses from ewes fed E+ seed had smaller (P < 0.05) liver, pancreas, spleen and kidney weights compared to E-/E-. Fetal brain weight did not differ by fescue treatment and resulted in a larger percentage of brain to fetal body weight for E+ fescue, which is indicative of intrauterine growth restriction (IUGR). Muscle histology of fetal ST muscle revealed that primary muscle fiber number was reduced (P < 0.05) for E-/E+, E+/E-, and E+/E+ when compared to E-/E- fetuses. Secondary muscle fiber number and secondary:primary fiber ratio was increased (P < 0.05) for fetuses from E-/E+, E+/E-, and E+/E+ dams. miRNA sequencing showed differential expression (P < 0.01) of six novel miRNAs including: bta-miR-652_R+1, mdo-miR-22-3p, bta-miR-1277_R-1, ppy-miR-133a_L+1_1ss5TG, hsa-miR-129-1-3p, and ssc-miR-615 in fetal ST tissue. Several of these miRNA are involved in insulin resistance and KEGG pathway analyses showed that cellular energy metabolism, and intracellular and extracellular signaling may be also be affected by feeding E+ fescue seed during gestation.