Effect of Repeated Freezing and Thawing on Nguni Sperm Parameters Evaluated by Computer Assisted Sperm Analyzer System

Abstract

The aims of the current study were to assess the effect of double freezing and thawing on Nguni semen parameters. Semen was collected from Nguni bulls. The Sperm Class Analyzer^® system was used to evaluate sperm motility rates prior and post freezing, repeatedly. Semen samples were diluted with egg yolk citrate extender. Cooled semen samples were loaded into straws and placed inside the programmable freezer for freezing. The frozen semen straws were stored inside liquid nitrogen tank. The frozen semen straws were then thawed at 15°C (1^st and 2^nd freezing and thawing followed the same process) for a duration of 5 min and further assessed post-thawed at 0 and 15 min during in vitro liquid storage at 15°C. The treatment means were analyzed using Fisher’s protected t-test least. There was no significant differences recorded on raw semen sperm total motility (93.2%) and 1^st frozen-thawed at 0 min (82.6%), with recovery rate of 88.6% of the sperm total motility. There was a drastic decline observed in sperm total motility during the 1^st frozen-thaw at 15 min (77.6%), 2^nd frozen-thaw at 0 min (31.3%) and 2^nd frozen-thaw at 15 min (30.1%; P<0.05). In conclusion, the freezing and thawing process did not decrease the bull’s sperm total motility percentage during the 1^st freezing and thawing process, as compared with raw semen. However, a drastic decline was observed during the 2^nd freezing-thawing process, as compared with raw semen.