Author ORCID Identifier

https://orcid.org/0000-0001-6136-2337

Semester

Spring

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

christopher Ashwell

Committee Co-Chair

Ibukun Ogunade

Committee Member

Joe Moritz

Committee Member

Jennifer Stueckle

Abstract

Immune and metabolic disruption during weaning represents a major challenge to health and productivity in beef cattle. This dissertation tested the hypothesis that supplementation with multi-strain direct-fed microbials (DFMs) modulates immune regulation and metabolic pathways associated with adaptation to weaning stress. To address this, whole-blood transcriptomics and plasma metabolomics were used to evaluate molecular and metabolic responses in newly weaned beef steers during the receiving period. Transcriptomic analysis identified differential expressions of genes associated with immune signaling and inflammatory regulation, indicating modulation of immune-related pathways without changes in growth performance. Metabolomic analysis revealed alterations in circulating metabolites related to amino acid metabolism, energy pathways, and oxidative balance, with enrichment of key metabolic pathways during and after supplementation. When considered together, these findings suggest coordinated changes in immune and metabolic processes during the weaning transition. Overall, this work provides systems-level insight into molecular responses associated with DFM supplementation and supports future research aimed at understanding mechanisms of adaptation and developing precision nutritional strategies in beef cattle.

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