Evaluation of Enrofloxacin for Use in Cryopreservation of Zebu Bull (Bos indicus) Semen

Abstract

Aim: The present study was designed to evaluate enrofloxacin (EN), a fluoroquinolone broad-spectrum antibacterial drug for use in cryopreservation of Zebu bull semen. Materials and Methods: Semen was collected from three Zebu bulls of the Sahiwal breed (Bos indicus) for 3 weeks (replicates) for each experiment. Experiment I: semen samples were cultured for isolation of bacteria and in vitro sensitivity tests against streptomycin, penicillin, and EN. Proteus spp., Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli were isolated. P. aeruginosa was found to be resistant to streptomycin and penicillin (SP), while Proteus spp. was resistant to streptomycin. EN effectively inhibited the growth of all four bacteria in an in vitro sensitivity test. Experiment II: in vitro dose toxicity of EN (0-2000 μg/mL) for bull sperm was assessed in 2.9% sodium citrate buffer. EN up to a concentration of 1200 μg/mL was found to be safe for motility and viability of bull spermatozoa. Experiment III: semen was cryopreserved in a tris-citric acid extender containing either SP or EN (400 μg/mL) or without antibiotics as the control. Results: Post-thaw sperm motility was found to be higher in the extender containing EN and SP compared to control. Nevertheless, sperm viability was recorded higher (p < 0.05) with EN compared to SP and control. Sperm chromatin integrity did not differ (p > 0.05) in EN, SP, and controls. The total aerobic bacterial count was recorded as zero in the extender containing EN compared to SP and control. The fertility rate was higher (p < 0.05) with 400 μg/mL EN (59%) compared to SP (44%). Conclusions: It is concluded that EN is capable of controlling the bacterial load in frozen Zebu bull semen, resulting in a higher fertility rate under field conditions.

Keywords: antibiotics; bacteriospermia; bull semen; enrofloxacin.