Background: Antibiotic-free approaches to boar semen preservation are gaining importance to counter emerging antimicrobial resistance. Hypothermic storage at 5 °C, instead of the conventional 17 °C, is a promising strategy to eliminate antibiotics still commonly used in extenders. For practical adoption, the method must be simple and compatible with on-farm routines. Objective: To assess fertility when cooling was initiated on farm one day after delivery, and to evaluate the robustness of cold-stored semen to temporary warming and subsequent re-cooling, mimicking typical handling on insemination days. Methods: Individual ejaculates (n = 34) from six boars were extended in Androstar® Premium either without antibiotics (5 °C) or with gentamicin (17 °C control). One day after collection, antibiotic-free doses were cooled on farm to 5 °C and used alongside controls in routine insemination of 270 sows. Sperm quality was evaluated by computer-assisted semen analysis and flow cytometry, and bacterial counts were monitored. In a separate test, cold-stored doses were exposed to 20 °C for 60 min and re-cooled to 5 °C. Results: Farrowing rates and litter sizes did not differ between groups (p > 0.05). In antibiotic-free samples after 120 h, bacterial counts were mostly not detectable or low (80%, comparable to controls (p > 0.05). Temporary warming did not affect sperm quality or bacterial counts. Conclusions: Antibiotic-free semen storage at 5 °C is easy to implement in practice and maintains fertility under field conditions. Broader validation under routine conditions is encouraged in support of the One Health concept.
Reckinger et al. (Tue,) studied this question.