Effect of Freezing on Spermatozoa from Tigaie Rams Belonging to the Mountain Ecotype

Our aim was to study the influence of freezing on the viability and frequency of abnormalities in frozen ram spermatozoa. Sperm was collected form 20 rams belonging to the mountain ecotype of the Tigaie breed using the artificial vagina technique and volume and motility were assessed. Afterward it was diluted with Tryladil (1:4) supplemented with 20% egg yolk and heated at 37°C. Subsequently the temperature decreased at a rate of 0.2°C/minute until reaching 4°C and an equilibration time of 2 hours followed. During this time the diluted sperm was packaged in 0.25 ml straws. After sealing these were kept 6 cm above liquid nitrogen level for 13 minutes (-120°C) and then plunged into nitrogen. Volume, motility and concentration were assessed before freezing. After thawing sperm morphology was assessed using Hancock’s method and at the same time the endurance (at 10, 30 and 60 minutes) and HOST tests were performed. The highest motility (0.40) was graded at 30 minutes. It could be correlated with the increased percentage of HOST positive spermatozoa, 27.78%. The percentage of abnormal spermatozoa was also high (47.89%), 38.44% of them having acrosome flaws. Cryopreservation has a negative effect on the characteristics of sperm cells from Tigaie rams belonging to the mountain ecotype.