Abstract / Summary
Abstract Background Semen doses for artificial insemination include antibiotics to inhibit bacterial growth but this routine use of antibiotics may contribute to the emergence of antimicrobial resistance. An alternative is needed to inhibit growth of the seminal bacterial load. Recently, protocols for slow cooling of boar semen were developed, raising the possibility that hypothermic storage could replace antibiotics in semen doses. The aim of this study was to determine the effects of hypothermic storage on bacterial counts in boar semen doses stored in the presence or absence of antibiotics. Aliquots were taken for bacteriology and sperm quality analyses on arrival, and for bacteriology on day 3 and 7. Results On arrival, bacterial counts were similar in samples with and without antibiotics ( p = 0.28). Notably, bacteria were isolated even from samples containing antibiotics, indicating potential antimicrobial resistance to the antibiotics in the extender. The bacterial load in samples containing antibiotics remained stable during storage. However, in samples without antibiotics, bacterial counts increased substantially at Day 3 and Day 7 in samples stored at 17 °C ( p < 0.0003 and p < 0.0001, respectively), although there was no significant increase in samples stored without antibiotics at 4 °C ( p = 1.0). Considerable variation in bacterial count was observed among individual samples. Conclusions These results indicate that although hypothermic storage can prevent bacterial multiplication in some antibiotic-free boar semen samples, it is not consistently effective across all samples. Therefore, hypothermic storage alone is not sufficient to inhibit bacterial growth; alternative strategies are clearly needed to help control bacterial contamination in pig insemination doses.