Epsilon poly-lysine in buffalo semen extender: A step towards reducing the development of antibiotic resistance

The use of antibiotics in semen extenders can contribute to the development of antibiotic resistance. The objective of the study was to evaluate epsilon-polylysine (Ɛ-PL) as a substitute for antibiotics in the buffalo semen extender. For this, 20 semen ejaculates were collected from four Murrah buffalo bulls. Each ejaculate was divided into three equal aliquots and extended into an egg yolk-based semen extender containing either antibiotics (strepto-penicillin) or different concentrations of Ɛ-PL (0.64 and 1.28 g/L) to make the final concentration 80 million sperm/mL and cryopreserved as per the standard procedure. The antibiogram sensitivity test confirmed that Ɛ-PL is an effective antimicrobial against microbes present in buffalo semen ejaculates. Furthermore, the addition of Ɛ-PL in the semen extender significantly reduces the colony forming unit (CFU)/mL in cryopreserved semen equivalent to strepto-penicillin. The sperm motility and kinematic parameters assessed by a computer-assisted sperm analyser showed that Ɛ-PL did not inhibit either sperm motility not kinematic parameters of cryopreserved sperm. The flow-cytometric evaluation of frozen-thawed sperm revealed interesting results. The extender supplemented with Ɛ-PL protected sperm acrosome and mitochondrial membrane potential greater than the extender supplemented with strepto-penicillin. Further, Ɛ-PL reduced significantly the production of superoxide anions from mitochondria during the cryopreservation process. In this way, Ɛ-PL may be a suitable alternative to antibiotics in semen extenders. In conclusion, Ɛ-PL at a concentration of 0.64 g/L acts as an effective antimicrobial as well as antioxidant in semen extender for cryopreservation of buffalo sperm.