Effect of Extender and Equilibration Time on Post Thaw Motility and Chromatin Structure of Buffalo Bull (Bubalus Bubalis) Spermatozoa

Objective: the aim of the present study was to investigate the effects of four equilibrationtimes (2, 4, 8 and 16 hours) and two extenders (tris or bioxcell®) on cryopreservationof buffalo semen.materials and methods: in this experimental study, split pooled ejaculates (n=4), possessingmore than 70% visual sperm motility were divided in two aliquots and diluted in bioxcell® and tris-citric egg yolk (tce) extenders. semen was cooled to 4?c within 2 hours,equilibrated at 4?c for 2, 4, 8 and 16 hours, then transferred into 0.5 ml french straws,and frozen in a programmable cell freezer before being plunged into liquid nitrogen. postthawmotility characteristics, plasma membrane integrity, acrosome morphology and dnaintegrity of the buffalo sperm were studied after thawing.results: there were significant interactions between equilibration times and extendersfor sperm motility and membrane integrity. post thaw sperm motility (pmot), progressivemotile spermatozoa (prog), plasma membrane integrity (pmi) and normal apical ridge(nar) measures were lower for sperm equilibrated for 2 hours in both tce and bioxcell®extender compared to others equilibration times. pmot, pmi and nar for sperm equilibratedfor 4, 8 and 16 hours showed no significant differences in either extender, althoughprog measures were superior in bioxcell® compared to tce at all equilibration times(p < 0.05). kinematic parameters such as average path velocity, curvilinear velocity andlinearity in the bioxcell® extender were superior to those in the tce extender studied. incontrast to motility and viability, the dna integrity of post thaw spermatozoa remainedunaffected by different equilibration times.conclusion: equilibration time is necessary for preservation of the motility and integrity ofbuffalo sperm membranes. equilibration times of over than 2 hours resulted in the greatestpreservation of total semen parameters during cryopreservation. there were no significantinteractions between equilibration times over 4 hours and type of extender which lead togreater post thaw sperm survival.