Theses and Dissertations

ORCID

https://orcid.org/0000-0003-3644-6576

Advisor

Ngeukam-Feugang, Jean

Committee Member

Lemley, Caleb

Committee Member

Vance, Carrie

Committee Member

Tesfaye, Dawit

Date of Degree

5-15-2026

Original embargo terms

Visible MSU Only 6 months

Document Type

Dissertation - Campus Access Only

Major

Agricultural Science (Animal and Dairy Science)

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Agriculture and Life Sciences

Department

Department of Animal and Dairy Sciences

Abstract

Boar semen quality is influenced by various factors, including environmental conditions and changes in the biochemical composition of seminal plasma. Seminal plasma (SP) contains biomolecules, including proteins, metabolites, and extracellular vesicles (EVs). The primary objectives of this dissertation were to investigate the roles of seminal plasma–derived EV microRNAs, metabolites, and microbial composition in high-quality (Passed) and low-quality (Failed) seminal plasma (SP), and to evaluate their associations with boar semen quality. Semen was collected from Duroc boars at a commercial boar stud and assessed for sperm quality. Samples were centrifuged, and SP supernatants were extracted for subsequent analysis using SP-EV miRNA sequencing, untargeted metabolomics, and 16S/ITS rRNA gene sequencing. Statistical significance was set at p < 0.05. Differential expression analysis of miRNAs revealed 28 downregulated (e.g., ssc-miR-223, ssc-miR-202-3p, ssc-miR-205) and two upregulated (ssc-miR-551a and ssc-miR-7-3p) in the Passed SP-EV group. Upregulated miRNAs were involved in sperm-related biological processes and the PI3K-Akt, regulation of actin cytoskeleton, and ErbB signaling pathways (p < 0.05). In the untargeted metabolomics analysis, several metabolites were identified as potential seasonal indicators of boar semen quality during the summer (ergothioneine, Nona-2,4,7-trienedioylcarnitine, indole-3-methyl acetate, and avocadyne) and winter (LysoPC, dopamine, tyrosine, and betaine). These metabolites were associated with critical sperm functions, including energy metabolism, antioxidant defense, and capacitation, and were enriched in amino acid metabolic pathways. Additionally, microbial analysis demonstrated high relative abundances of the bacterial phyla Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Among the alpha diversity metrics, only the Shannon index differed significantly (p = 0.038), with no significant difference observed for beta diversity. Correlation analysis revealed a negative association between the bacterial phylum Tenericutes and sperm concentration (r = -0.90; p = 0.014). Furthermore, linear discriminant analysis identified several microbial signatures, including Rhodococcus, Streptococcus, and Sphingomonas, which were enriched in the SP group, whereas Lactobacillus and Empedobacter were enriched in the SF group. Their enrichment may indicate microbial dysbiosis that negatively influences sperm function and semen quality. In conclusion, these findings suggest that boar SP-EV miRNAs, metabolites, and microbiota could serve as potential indicators of semen quality and may help enhance reproductive efficiency in swine production systems.

Sponsorship (Optional)

U. S. Department of Agriculture, Agricultural Research Service, project 6066-31000-015-00D

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