In many studies the presence of bacteria in boar semen is associated with conservation or fertility issues [1]. Some bacteria may be associated with significant decreases in sperm motility, litter size, or impairment of sperm capacitation in vitro, making bacteriospermia a major factor affecting the quality of the extended semen [2]. The costly and time-consuming methods of culture are still unable to reveal full bacterial diversity. Reducing the use of antibiotics used to secure commercialized semen is also a major concern. Metagenomic analysis based on the high-throughput sequencing of a portion of the gene encoding 16S rRNA makes it possible to exploit the microbiota profile (its taxon composition) and its diversity indices (related to the number of taxa observed in a microbiota at a given time). We applied these methods in a multi-center pilot study to determine which parameters influence the composition of the porcine seminal microbiota.
A total of 192 samples were collected (Collectis® or Safemate), the microbial DNA extracted from these semen samples was sequenced (Miseq, Illumina). Statistical analysis revealed a significant difference in the microbial composition and diversity indices of the microbiota from different semen production centers. One of the main variables associated with these differences was the type of soil on which the boar was bred. For semen samples taken before dilution, animals reared on slatted floor had a higher microbial diversity and a different seminal microbial profile than animals reared on sawdust. After dilution, these differences converged towards a similar diversity and composition. All the semen tested in this analysis showed fertility indicators in accordance with the industry standards.
This pilot study demonstrated that high-throughput sequencing can be considered for the quality control of semen by assessing the conformity of the porcine seminal microbiota.