Author ORCID Identifier

https://orcid.org/0009-0006-4355-382X

Semester

Summer

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Ibukun Ogunade

Committee Co-Chair

Ida Holaskova

Committee Member

Ida Holaskova

Committee Member

Janet Tou

Abstract

Immune system function is critical to maintaining the health and increasing productivity of cattle, affecting both their growth and their disease resistance. In an efficient immune system, the liver assumes an integral function in detoxification and metabolic processes and contributes substantially to overall production and immunity. In this study, we evaluated the hepatic mRNA expression of genes involved in innate and adaptive immunity in crossbred beef steers with either a positive or negative residual body weight gain (RADG). Positive-RADG beef steers (n = 8; RADG = 0.76 kg/d) and negative-RADG beef steers (n = 8; RADG = -0.64 kg/d) were identified from a group of 108 growing crossbred beef steers (average BW = 286± 380kg) after a 56-d performance testing period. At the end of the 56-d period, liver tissue samples were collected from the beef steers for total RNA extraction and cDNA synthesis. The mRNA expression of 84 genes involved in innate and adaptive immunity were analyzed using pathway-focused PCR-based arrays. The mRNA expression of genes with false discovery rate-adjusted P-values (FDR) ≤ 0.05 and absolute fold change (FC) ≥ 1.2 were determined to be differentially expressed. Out of the 84 genes analyzed, four genes (IL-2, MYD88, CD-80, NFkB-1) were differentially expressed. All four genes were upregulated in positive compared with negative-RADG beef steers. Gene ontology pathway enrichment analysis of the differentially expressed genes revealed that pathways related to positive regulation of interleukin-17 production, cellular response to lipopolysaccharide, and positive regulation of lymphocyte activation were enriched in the positive-RADG steers (P ≤ 0.05). In conclusion, our study revealed that positive-RADG beef steers had increased expression of genes and pathways involved in pathogen recognition and initiation of responses to effectively fight off infections while mitigating excess inflammatory reactions compared to negative-RADG steers, which potentially explains, in part, the improved feed efficiency of these beef animals.

Keywords: feed efficiency, immunity, pathogen recognition, gene expression, liver, beef steer

Download

Share

COinS