Study of the effects of low temperatures on the morphological status of ram spermatozoa

Abstract

The aim of the study was to evaluate how the process of cryopreservation influenced the morphological status of ram sperm. The experiment was carried out with 26 sexually matured, pure bred rams during their breeding campaign. The animals were divided in two groups according to the breed – 15 rams from Synthetic Population of Bulgarian Milk (SPBM) and 11 rams from Sofia breed (SB). The sperm morphology was evaluated under microscope (Nikon Eclipse E200, Japan) by staining with SpermBlue (Microptic, Spain), performed according to the manufacturer's protocol, and observed under bright field with magnification of ×40. Cryopreservation of semen straws was done by the method of Cassou (1964). After cryopreservation, the percentage of spermatozoa with normal morphology decreased and those with abnormal morphology increased. This difference was more pronounced at rams from SPBM compared to SB rams. After freezing, the percentage of spermatozoa with damage to the head at rams from both breeds increased. The percentage of the spermatozoa with damage in the midpiece and the tail was higher and significant (P<0.001) for the SPBM rams. The low temperatures of cryopreservation had a detrimental effect to the rams’ sperm structures. This damaging effect was much stronger for the rams from SPBM breed compared to rams from Sofia breed.