The role of different trehalose concentrations and cooling rates in freezing of ram semen

The aim of this study was to determine the influence of different cooling rates and trehalose concentrations on standard semen parameters after the freezing-thawing of ram spermatozoa. Ejaculates collected using artificial vagina from 4 Akkaraman rams were evaluated and pooled at room temperature. Semen samples diluted with a Tris-based extender containing different concentrations (50, 100 and 150 mM) of trehalose and no additives (control) were cooled to 5°C and frozen at slow (a rate of 0.5°C/min from 5°C to -25°C; -50°C/min from -25°C to -130°C), and fast (a rate of 10°C/min from 5°C to -25°C; -50°C/min from -25°C to -130°C) cooling rates and plunged into liquid nitrogen. Frozen straws were thawed individually at 37°C for 20 sec in a water bath for evaluation. In conclusion, 50 and 100 mM trehalose and slow cooling rate were found to significantly (p<0.05) improve the freezability of ram spermatozoa which were assessed regarding post-thawing sperm motility, morphologic sperm abnormalities, viability and membrane integrity. But, 100 mM trehalose concentration and slow cooling rate were observed superior than other treatment groups.