Date of Award
Doctor of Philosophy (PhD)
Animal and Veterinary Sciences
Dr. Susan Duckett, Committee Chair
Dr. Jim Strickland
Dr. John Andrae
Dr. William Bridges
Tall fescue is the primary cool season perennial forage grass in southeastern US for grazing livestock. Tall fescue the is known to be drought tolerant , disease resistant, grazing tolerant and overall very hardy. Many of these attributes common to fescue are due to a symbiotic relationship between the fescue plant and an endophyte, Epichloë coenophiala , which produces a class of mycotoxins known as ergot alkaloids. These ergot alkaloids are similar in structure to several biogenic amines, such as epinephrine, norepinephrine, and dopamine. When consumed, ergot alkaloids cause a syndrome known as fescue toxicosis which causes problems with weight gain and reproduction and is known to suppress circulating prolactin conc ergot alkaloid found in endophyteentrations. Ergovaline, the predominant infected tall fescue, is a potent vasoconstrictor and could impair uteroplacental blood flow during gestation.
Three live animal experiments, two histological studies, and expression project were conducted one gene to determine the effect of ergot alkaloids uteroplacental development and f etal growth. The first study sou on ght to determine how feeding endophyte during MID (d 35 –- infected (E+) or endophyte 85) and LATE (d 86 –- free (E) tall fescue seed 133) gestation would alter maternal performance and placental development. Results su ggested that exposure to ergot alkaloids during LATE gestation had the greatest impact on placental development as indicated by placentome weight. The resulting placental insufficiency reduced total fetal weight per ewe by 15% for ewes on E+ fescue ii iii seed during LATE gestation. It was hypothesized that exposure to E+ fescue seed during LATE gestation stunts development of the placenta, likely due to the vasoconstrictive effects of ergot alkaloids, during the crucial period of placental remodeling when the majority of fetal growth occurs.
The second study analyzed gene expression through the use of RNAsequencing technology to assess differences in the cotyledonary transcriptome of ewes consuming E+ fescue seed treatment from d 35 – 133 of gestation. This study concluded that, at d 133 of gestation, vascular and growth factors were not impacted based on E+ fescue seed treatment. Clusters of upregulated genes associated with responses to glucose, carbohydrates, and xenobiotic stimuli and lipid and protein metabolism were upregulated in ewes on E+ fescue treatment from d 35 – 133 of gestation. The complement and coagulation cascade and PPAR signaling pathway were also found to be enriched for ewes on E+ treatment. The increase in protein and lipid metabolism for ewes on E+ fescue seed treatment may work to supply the fetus with additional substrates. Additionally, an upregulation in carbohydrate biosynthesis and enrichment of the coagulation and complement cascade have been linked to placental insufficiency in humans and was also noted for ewes on E+ fescue seed treatment.
The third study, the initial histological evaluation, sought to assess how feeding tall fescue seed containing ergot alkaloids from d 35 – 133 of gestation affects the structure and vascular development of the ovine placenta. Regions of iv residual amorphous connective tissue within the fetal villi and the luminal vessel area were increased in the placentome of ewes on E+ fescue treatment. This suggests that exposure to ergot alkaloids from d 35 – 133 of gestation slowed placental remodeling and altered vasculature development of the ovine placenta which may limit the capacity for fetal growth during late gestation.
The second live animal project focused on how feeding tall fescue seed containing ergot alkaloids during MID and/or LATE gestation alters parturition and maternal characteristics, mammary development and lactation, and lamb growth pre- and post-weaning. All E+ fescue seed treatments (E-/E+, E+/E-, and E+/E+) experienced depressed milk production by 65 – 85% compared to E-/E- treatment. LATE gestational exposure appeared to have a greater impact immediately following parturition while MID gestational exposure limited the capacity for long term production. Additionally, E+/E+ fescue seed treated dams produced lambs with reduced weaning weights and overall ADG through the preweaning period as well as a reduced likelihood of successful breeding during their first year.
The final live animal project, which also includes a histological evaluation, sought to evaluate the impact that ergot alkaloid consumption has on fetoplacental growth and development at multiple stages during the LATE gestational period using serially harvested sheep. This study concluded that exposure to E+ fescue seed beginning at d 86 of gestation stunts the placental remodeling process thereby limiting the capacity for nutrient exchange to the fetus. It was hypothesized that the placental insult caused by exposure to ergot alkaloids found in E+ fescue seed occurs noticeable by d 110 of gestation. Though 133, the fairly quickly post exposure the placenta appears and is compensate by d previously reported reductions in fetal weight at d 133 and in birth weight may represent the placenta’s inability to compensate for the earlier pe of restricted fetal growth.
Britt, Jessica Lynn, "The Impact of Ergot Alkaloid Consumption During Gestation on Maternal Performance and Fetoplacental Development" (2019). All Dissertations. 3165.