Freezing of Spermatozoa from Tigaie Rams Belonging to The Hill Ecotype

Abstract

Our purpose 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 hill 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 straws. After sealing these were kept 6 cm above liquid nitrogen level for 13 minutes (-120°C) and then plunged into nitrogen (-196,8oC). Volume, motility and concentration were assessed before freezing. After thawing the Hancock, endurance (at 10, 30 and 60 minutes) and hypoosmotic tests were performed. Abnormalities of the head, midpiece and tail were also investigated using the Hancock method. After thawing motility sperm decreased to 0.32-0.42, while only 25% of the spermatozoa were HOST positive. The percentage of abnormal spermatozoa was as high as 50%, the acrosome being flawed in most cases (34.20%). Cryopreservation has a negative effect on sperm cells from Tigaie rams belonging to the hill ecotype.

Keywords

• freezing
• hill ecotype
• ram semen
• tsigaie