Physiological and immune responses to endophyte-infected tall fescue exposure in beef heifers: impacts on performance, metabolism, and immune cell transcriptomics

Fescue toxicosis, resulting from the consumption of ergot alkaloids present in endophyte-infected tall fescue, remains a significant challenge to beef cattle health and productivity. This research investigated the physiological and immune consequences of fescue toxicosis in twenty-four commercial Angus heifers housed in a feedlot system. Twelve heifers received endophyte-infected (E+) tall fescue seeds (ergovaline dose: 20 μg/kg BW/day), and twelve received endophyte-free (E−) control seeds, both provided as part of a total mixed ration for 49 days. Animals were allocated to dietary treatments with balanced genetic representation. The first study evaluated whether E+ tall fescue seeds could replicate symptoms of fescue toxicosis. Key performance metrics (body weight, dry matter intake, and feeding behavior), thermoregulation (rectal temperature and respiration rate), and liver function (serum biochemical profile) were measured. E+ heifers showed significant reductions in body weight, dry matter intake, feeding rate, and meal size (P<0.05), along with elevated rectal temperatures and respiration rates emerging within two weeks of exposure. Serum analysis revealed elevated aspartate aminotransferase (AST), reduced alkaline phosphatase (ALP), and cholesterol levels in E+ heifers (P < 0.05), indicating hepatic and metabolic disruption. The second study investigated immune and metabolic disruptions by analyzing hematological and transcriptomic changes in peripheral blood mononuclear cells (PBMCs) on day 49. E+ heifers exhibited hematological alterations, including a reduced neutrophil-to-lymphocyte ratio, segmented neutrophil percentages, and mean corpuscular hemoglobin concentration (MCHC), along with increased lymphocyte percentages and basophil counts (P < 0.05). RNA sequencing of PBMCs identified 64 differentially expressed genes (11 upregulated and 53 downregulated; FDR < 0.05). Functional enrichment analysis revealed disruptions in pathways related to vascular development, inflammation, immune response, apoptosis, neuroinflammation, cholesterol metabolism, cytokine signaling, and adaptive thermogenesis. Together, these findings confirm that feeding endophyte-infected tall fescue seeds can mimic pasture-based toxicosis and induce systemic physiological, metabolic, and immune disruptions. The results revealed transcriptomic signatures in immune cells that offer mechanistic insight into the physiological and immune-related pathways disrupted by ergovaline exposure in beef cattle.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Godoy Takashe, Joao Vitor

Contributors dc:contributor

• Braz, Camila U.
• McCann, Joshua C
• Antonson, Adrienne

• Beef Cattle
• Ergot Alkaloids
• Fescue Toxicosis
• Gene Expression
• Immune Dysregulation
• Pbmcs.

Statement dc:rights

• Copyright 2025 Joao Godoy Takashe

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130227

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130227