Preliminary study on effects of bovine frozen semen storage using a liquid nitrogen-independent method on the quality of post-thaw spermatozoa

摘要

Frozen semen of eight bulls was used to assess effects of storage temperature and length of storage time on frozen-thawed bovine sperm quality. In experiment 1, 25 straws of frozen semen of each bull were allocated to 3 groups. The control was still maintained in liquid nitrogen (LN2). The rest were abruptly moved from LN2 to -80 degrees C and -30 degrees C mechanical freezers, respectively. After thawing, it was found that the sperm motility, vitality and membrane integrity were comparable (P>0.05) between the control and the -80 degrees C samples and were significantly inferior (P0.001) in the -30 degrees C samples, irrespective of storage time (1-day, 1-week and 1-month). In experiment 2, two out of the three parts (16-18 straws) of frozen semen of each bull were rapidly removed from LN2 and further kept in the freezer (-80 degrees C). One day before being thawed, half of the samples in the freezer were promptly put back to LN2. The results showed that the frozen-thawed sperm quality was not significantly affected (P>0.05) both by storage temperature (-196 degrees C, -80 degrees C and -80 & -196 degrees C) and storage time [day-2, day-8 (1-week) and day-31 (1-month)]. At the same storage times, the quality measures at different temperatures were not significantly different from one another (P>0.05). In conclusion, a -80 degrees C mechanical freezer was as effective as LN2 in preserving in vitro quality of frozen-thawed bovine spermatozoa throughout 1-month of storage. When required for use, frozen semen stored in the freezer could be thawed immediately or transferred to the LN2 tank for thawing elsewhere. (C) 2016 Elsevier B.V. All rights reserved.