Ergot alkaloid exposure during gestation alters: 3. Fetal growth, muscle fiber development, and miRNA transcriptome1

Abstract

The objective of this study was to assess how exposure to ergot alkaloids during 2 stages of gestation alters fetal growth, muscle fiber formation, and miRNA expression. Pregnant ewes (n = 36; BW = 83.26 ± 8.14 kg; 4/group; 9 groups) were used in a 2 × 2 factorial arrangement with 2 tall fescue seed treatments [endophyte-infected (E+) vs. endophyte-free (E−)] fed during 2 stages of gestation (MID, days 35 to 85 vs. LATE, days 86 to 133), which created 4 possible treatments (E−/E−, E+/E−, E−/E+, or E+/E+). Ewes were individually fed a total mixed ration containing E+ or E− fescue seed according to treatment assignment. Terminal surgeries were conducted on day 133 of gestation for the collection of fetal measurements and muscle samples. Data were analyzed as a 2 × 2 factorial with fescue treatment, stage of gestation, and 2-way interaction as fixed effects. Fetuses exposed to E+ seed during LATE gestation had reduced (P = 0.0020) fetal BW by 10% compared with E− fetuses; however, fetal body weight did not differ (P = 0.41) with E+ exposure during MID gestation. Fetuses from ewes fed E+ seed during MID and LATE gestation tended to have smaller (P = 0.058) kidney weights compared with E− fetuses. Liver weight was larger (P = 0.0069) in fetuses fed E− during LATE gestation compared with E+. Fetal brain weight did not differ by fescue treatment fed during MID (P = 0.36) or LATE (P = 0.40) gestation. The percentage of brain to empty body weight (EBW) was greater (P = 0.0048) in fetuses from ewes fed E+ fescue seed during LATE gestation, which is indicative of intrauterine growth restriction (IUGR). Primary muscle fiber number was lower (P = 0.0005) in semitendinosus (STN) of fetuses exposed to E+ during MID and/or LATE gestation compared with E−/E−. miRNA sequencing showed differential expression (P < 0.010) of 6 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 STN muscle. These miRNA are associated with glucose transport, insulin signaling, intracellular ATP, hypertension, or adipogenesis. This work supports the hypothesis that E+ tall fescue seed fed during late gestation reduces fetal weight and causes asymmetrical growth, which is indicative of IUGR. Changes in primary fiber number and miRNA of STN indicate that exposure to E+ fescue fed during MID and LATE gestation alters fetal muscle development that may affect postnatal muscle growth and meat quality.

Use of Oral Citrulline Administration as a Mitigation Strategy for Fescue Toxicosis in Sheep

“…Treatment began on d 86 of gestation and continued until parturition. This time period (d 86 to parturition) was chosen based on previous research that identi ed d86 to d133 as a critical time for fetal growth when exposed to E + tall fescue seed (Britt et al, 2019;Greene et al, 2019). Two ewes, H2O, were removed from the study after the start of treatment due to abortions, and one CITM ewe was removed due to having a singleton female.…”

“…Seed was fed to ewes daily in a total mixed ration (TMR) at a total dose level to supply 1772 µg hd − 1 d − 1 of ergovaline and ergovalinine and was based on previous research (Aiken et al, 2009;Duckett et al, 2014a;Britt et al, 2019). Seed and TMR samples were taken for nutrient analysis, and daily rations were established to meet NRC requirements for gestating ewes from d 86 to parturition (Britt et al, 2019). Seed was mixed by hand with TMR daily and fed to each ewe individually.…”

“…Unfortunately, the fungus also produces ergot alkaloids (Stuedemann and Hoveland, 1988), which have been linked to decreased weight gain (Schmidt et al, 1982), reproductive problems (Peters et al, 1992;Porter and Thompson, 1992), and vasoconstriction (Dyer, 1993;Klotz et al, 2010;Aiken and Flythe, 2014). Feeding endophyte-infected (E+) fescue to pregnant livestock has been reported to cause intrauterine growth restriction (IUGR) that is evident at d 133 of gestation in sheep (Greene et al, 2019) and at birth in sheep and cattle (Watson et al, 2004;Duckett et al, 2014a). Reductions in fetal weight caused by ergot alkaloid exposure are speculated to be due to placental insu ciency caused by increased vasoconstriction (Britt et al, 2019).…”

“…Feeding endophyte-infected (E+) fescue to pregnant livestock has been reported to cause intrauterine growth restriction (IUGR) that is evident at d 133 of gestation in sheep (Greene et al, 2019) and at birth in sheep and cattle (Watson et al, 2004;Duckett et al, 2014a). Reductions in fetal weight caused by ergot alkaloid exposure are speculated to be due to placental insu ciency caused by increased vasoconstriction (Britt et al, 2019). Additionally, Klotz et al (2019) found that ovine dams dosed with ergot alkaloids from tall fescue seed had increased vasoconstriction in umbilical arteries.…”

“…Reductions in fetal weight caused by ergot alkaloid exposure are speculated to be due to placental insu ciency caused by increased vasoconstriction (Britt et al, 2019). Additionally, Klotz et al (2019) found that ovine dams dosed with ergot alkaloids from tall fescue seed had increased vasoconstriction in umbilical arteries. Little research has been conducted to determine if the oral administration of citrulline may improve lamb birth weight or IUGR associated with dam consumption of ergot alkaloids.…”