Media viscosity affects post-thaw ram sperm rheotactic behaviour

The aim of this experiment was to assess the effect of media viscosity on ram sperm motility, kinematics and rheotaxis in vitro by using methylcellulose as a media thickener. Frozen-thawed semen of three rams was thawed and diluted in Tyrode's albumin lactate pyruvate (TALP) media supplemented with 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6% and 0.7% w/v of methylcellulose. Sperm motility and kinematic characteristics were analysed using computer-assisted sperm analysis (CASA). The rheotactic behaviour was assessed in a microfluidic channel, and the number of spermatozoa that passed the 10 mm point of a microfluidic channel over a 2min period against a flow rate of 30 μm/sec was assessed. The use of media with higher viscosity (higher levels of methylcellulose) resulted in significantly lower (p < .05) sperm motility and kinematic parameters. Moreover, higher levels of methylcellulose reduced (p < .05) the number of spermatozoa that exhibited positive rheotaxis. In conclusion, viscosity affected the kinematic properties and rheotactic behaviour of ram sperm.