Navigating bacterial contamination and antimicrobial resistance in boar semen for artificial insemination.

The global rise in antimicrobial resistance (AMR) has intensified calls for responsible antimicrobial use in livestock farming, including the Australian pork industry. While stewardship efforts largely focus on husbandry and biosecurity, the routine inclusion of antimicrobials in chilled boar semen extenders used for artificial insemination remains relatively underexamined. Despite widespread use, international studies consistently report bacteriospermia in extended semen, raising concerns regarding the efficacy of current practices and their contribution to AMR development. Australia's closed-herd system provides a unique opportunity to investigate bacterial dynamics within a contained environment; however, the seminal microbiota and associated AMR profiles remain poorly characterised. This review synthesises evidence from peer-reviewed literature, industry reports, and international guidelines to critically examine the composition of boar seminal microbiota, sources of bacterial contamination, and environmental influences on bacterial load. It explores the impacts of bacteriospermia on sperm quality and fertility, and it critically evaluates the rationale for antimicrobial inclusion in semen extenders, including commonly used agents such as gentamicin and neomycin and, in some cases, critically important antimicrobials like ceftiofur and enrofloxacin. Emerging non-antibiotic alternatives, including natural antimicrobials, nanoparticles, and probiotics, are discussed in the context of their feasibility and potential role in reducing AMR risk.