Effect of different thawing temperatures on viability, kinematic parameters and progressive motility of frozen goat sperm
Caprine artificial insemination (AI) is generally based on the use of frozen semen straws, cryopreserved in liquid nitrogen. Thawing straws requires appropriate methods. The aim of the current study was to determine the best among different practical methods of thawing on the total motility, progressive motility, vitality and kinematic parameters of caprine semen such as: (i) curvilinear velocity (VCL) ; (ii) average path velocity (VAP) ; (iii) straight line velocity (VSL) ; (iv) amplitude of lateral head displacement (ALH) ; (v) beat cross-frequency (BCF) ; (vi) wobble coefficient (WOB, %) ; (vii) linearity (LIN, %) ; and (viii) straightness (STR, %). All of these parameters were measured during a short-term incubation period, in order to adopt the most efficient method for preserving sperm qualities. We thawed goat semen straws by four (04) different methods: 37 ºC for 40 seconds (s), 50 ºC for 15 s, 70 ºC for 5 s, and by using hot air (HA) at ±60 ºC for 10 s. The frozen semen was analyzed by the Computer Assisted Semen Analyzer (CASA) system. Our findings highlighted the existence of a significant effect of the thawing method on the sperm mobility and vitality, and came up with the most reliable method. In conclusion, on one hand, the method of thawing at 50 ºC/15 s gave better results concerning the total motility and vitality of goat frozen sperm. On the other hand, the 70 ºC/5 s thawing method was observed to show better performances regarding progressive mobility and dynamic parameters. Very poor results were obtained after thawing with HA±60 ºC/10 s. After two hours of post-thaw incubation at 50ºC/15 s, higher proportions of spermatozoa vitality and spermatozoa with fast and progressive movement were observed. However, it is unknown whether this minor difference affects in vivo fertilizing ability of thawed caprine frozen semen straws.