Dilution factor affects the ability of ram sperm to survive cryopreservation: Short communication

Abstract

In this preliminary study, the fresh and frozen-thawed sperm from the original Valachian sheep breed were analysed for its quality. Semen was collected from two rams by electroejaculation and used for motility analysis using computer-assisted sperm analysis immediately after collection and following 60 and 120 min of incubation at 37 °C, or for rapid freezing. Semen was equilibrated at 15 °C for 20 min and diluted with a commercial diluent OviXcell (IMV Technologies) supplemented with 100 mM trehalose to a ratio of 1:1 (DR 1:1 group) or 1:2 (DR 1:2 group) (v:v). After 90 min of equilibration at 5 °C, the straws were suspended horizontally in liquid nitrogen vapours for 10 min before being plunged into a liquid nitrogen for storage. After one month, the straws were thawed by immersing into a water bath at 38 °C for 60 s. Sperm motility analysis was done immediately after thawing and after 30 and 60 min of incubation at 37 °C, as stated above. Our results showed that the dilution ratio has considerable effect on ram sperm survivability. Higher percentage of total motility and progressive movement (P ≤ 0.05) was found in the DR 1:2 when compared to the DR 1:1 group. In addition, our results confirmed inter-male variability in the susceptibility to the cryopreservation process. Nevertheless, results of this study are of preliminary character. Experiments using higher number of samples (individuals) as well as other methodology approaches need to be tested in order to find the best procedure for semen cryopreservation of Slovak national sheep breeds.