Abstract

Semen quality is a key determinant of reproductive performance in breeding boars, and emerging evidence suggests the seminal microbiome may influence sperm function. However, the composition of the seminal plasma microbiome and its relationship to sperm quality remain poorly characterized. This study aimed to investigate the microbial composition of boar seminal plasma and its association with sperm quality. Semen ejaculates collected from Duroc boars were analyzed and classified as Passed (≥70% normal morphology) or Failed (<70% normal morphology). Seminal plasma was isolated by centrifugation and analyzed using 16S/ITS rRNA gene sequencing. The dominant bacterial phyla were Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. The most abundant genera included Porphyromonas, Bacteroides, and Cladosporium. Only the Shannon diversity index was significantly higher in Failed samples for the bacterial microbiome (p = 0.038). Furthermore, correlation analysis showed a negative association between Tenericutes and sperm concentration (r = −0.90; p = 0.014). Linear discriminant analysis identified microbial biomarkers associated with sperm quality, including Rhodococcus, Sphingomonas, Lactobacillus, Streptococcus, and Empedobacter. The increased abundance of these genera in Failed samples suggests disruption of the normal seminal microbial community. In conclusion, boar seminal plasma harbors a distinct bacterial and fungal microbiome that is associated with sperm morphology.

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