The antibacterġal effect of sericin in the short- term storage of rabbit sperm

Tuzlalıoğlu G. Aydin Adnan Menderes University Institute of Health Sciences, Department of Reproduction and Artificial Insemination (Veterinary) PhD Thesis, Aydin, 2025. Objective: In this study, the antimicrobial potential of sericin was investigated as an alternative solution to the problem of bacterial contamination encountered during the short-term preservation of rabbit semen. Aiming to reduce dependence on conventional antibiotics, the effects of sericin—added at various concentrations—on microbial load were evaluated in experimental groups. Additionally, the potential cytotoxic effects of sericin on sperm parameters were examined. Material and Methods: Semen samples were collected using the artificial vagina method from five New Zealand White male rabbits that were deemed genitally healthy. In the first experiment, the cytotoxicity level of sericin was analyzed by comparing control and sericin-treated groups. In the second experiment, in addition to control groups with and without antibiotics, groups containing different doses of sericin were formed. The semen samples were incubated at +5°C in Tris-citric acid-glucose (TCG) extender, and bacterial growth levels were compared at 0, 8, and 24 hours using microbiological culturing methods. In the third experiment, the swim-up technique was employed to remove seminal plasma from the semen samples, allowing for the assessment of its contribution to bacterial contamination. Results: In Experiment 1, the addition of 0.1% and 0.5% sericin had no significant adverse effects on sperm motility, membrane integrity, or viability, indicating that sericin was not cytotoxic under short-term storage conditions (P>0.05). In Experiment 2, although a reduction in bacterial counts was observed in the sericin-treated groups, the difference was not statistically significant (P>0.05). In Experiment 3, however, the removal of seminal plasma by the swim-up method resulted in a significant reduction in bacterial growth (P<0.05). Conclusion: The findings revealed that sericin possesses antimicrobial properties and, when used at appropriate concentrations, does not exert toxic effects on sperm cells. Moreover, seminal plasma was found to have a significant influence on bacterial growth. Keywords: Antimicrobial activity, Cytotoxic Effect, Rabbit Semen, Sericin, Swim-up.