The composition of the sperm microbiome in bulls (Bos taurus) may influence reproductive function. This study aimed to examine the taxonomic composition of the sperm microbiome in bulls to establish its possible link with semen quality. The study investigated the composition of the sperm microbiome of 21 Holstein bulls with varying sperm quality, including subfertile animals. The quality of sperm was assessed using standard methods. Analysis of the microbial community of the semen was performed using targeted next-generation sequencing (NGS). The data indicated significant species richness of microorganisms in the semen of the studied bulls. At least 15 different bacterial phyla were identified in the semen samples. Significant differences in the microbiome composition were revealed in samples of different sperm quality groups. Higher relative abundance of Actinobacteriota (from 1.9 ± 0.12% to 14.1 ± 1.02%) was observed in bulls with excellent semen quality. Bacteroides fragilis was detected in 75% of samples of low-quality sperm. At the same time, the analysis revealed individual differences in the microbial composition of samples. Our results indicate a link between the microbiome composition and qualitative indicators of the sperm of bulls. This suggests that the identified taxonomic markers may serve as additional bioindicators for assessing fertility in males.
Yildirim et al. (Mon,) studied this question.