The effects of antibiotic type and extender storage method on sperm quality and antibacterial effectiveness in fresh and cooled-stored stallion semen.

This study assesses the effects different antibiotics and their storage methods can have on the quality of stallion sperm and the control of bacterial growth. The findings reveal subtle differences in sperm quality based on the antibiotic used, with PEN-AMIK and MERO having the best antibacterial efficacy, but none of the antibiotics significantly controlling bacterial growth when faced with a high concentration of Pseudomonas aeruginosa.

Objective of the Research

• The main objective of this research was to determine the influence of different antibiotics and storage methods on the quality of stallion sperm and their effectiveness in controlling bacterial growth. Two experiments were conducted to achieve this aim.

Investigations and Findings

• Experiment 1 involved diluting ejaculates with extenders containing different antibiotics. These antibiotics were potassium penicillin G-amikacin disulfate (PEN-AMIK), ticarcillin disodium-potassium clavulanate (TICAR-CLAV), piperacillin sodium/tazobactam sodium (PIP-TAZ), and meropenem (MERO). In freshly extended semen, some antibiotic treatments showed slight differences in total sperm motility, curvilinear velocity, and viable acrosome-intact sperm. These differences were also noted in cool-stored semen, where slight differences were seen in curvilinear velocity and chromatin integrity.
• Experiment 2 involved diluting ejaculates with an extender that then either had no bacterial spiking, or a low or high dose of K. pneumoniae or P. aeruginosa added. After cooled storage, fewer signs of bacterial growth (colony forming units/ml or CFU/mL) were seen in the PEN-AMIK and MERO treatment groups as compared to the TICAR-CLAV or PIP-TAZ groups. Still, none of the antibiotic types completely controlled bacterial growth, especially when the semen had been spiked with a high concentration of P. aeruginosa.

Significance in Results

• The results reveal that the type of antibiotic used can subtly affect the quality of stallion sperm, specifically their motility, curvilinear velocity, chromatin integrity, and acrosome intactness. Additionally, these results show that while antibiotics can reduce bacterial growth, they may not completely eliminate it, especially in the case of high concentrations of certain bacteria.
• The experiment also showed that freezing and thawing the extender before usage didn’t negatively impact sperm quality or the efficacy of the antibiotics.
• Overall, it was concluded that of the antibiotics tested, PEN-AMIK and MERO yielded the best results in terms of both sperm quality and antimicrobial efficacy.

Impact of the Study

• The findings of this study could contribute to improvements in the process of storing and preserving stallion sperm, potentially increasing fertility rates of insemination.
• The findings also highlight the need for further investigation into effective methods to completely control bacterial growth in extended semen.