Glycine betaine improves survival of fresh bovine spermatozoa

Fresh spermatozoa from bulls established as ‘good freezers’ and ‘poor freezers’ (consistently ≥50% or <20% motile spermatozoa after cryopreservation, respectively) were incubated for 96 h in Tes/Tris–egg yolk or TALP–egg yolk media at 37°, 20°, 5° or 0°C. The TALP extender contained 0, 100 or 200 mM glycine betaine (GB) to test the hypothesis that GB would efficiently maintain spermatozoa function during long-term incubation. The percentage of motile spermatozoa declined over time in a temperature- and medium-dependent fashion. No spermatozoa were motile by 24 h incubation at 37°C or by 72 h incubation at 0°C, and there were no significant differences in the percentage of motile spermatozoa from either category of bull when spermatozoa were incubated in any media for less than 24 h. Spermatozoa from poor freezers were significantly more motile than spermatozoa from good freezers after 96 h at 20° or 5°C in TALP alone; however, GB at both 100 and 200 mM increased the percentage of motile spermatozoa in poor and good freezers and eliminated these differences. Overall, the presence of GB at either 100 or 200 mM significantly improved the percentage of motile spermatozoa at 20°, 5° and 0°C, but not at 37°C.