Effect of rapid freezing–thawing techniques on the sperm parameters and ultrastructure of Chinese Taihang black goat spermatozoa

• Ultrastructure of spermatozoa and sperm parameters of freezing‐thawing of goat semen was described.
• Using the computer‐assisted semen analysis (CASA) system evaluated the semen kinematic parameter and motility.
• Freezing–thawing resulted in a significant reduction in spermatozoa motility and increase in unmovable cells.
• Ultrastructure observations showed an intuitive deformity in sperm head (nucleus), midpiece and mitochondria causing by cryo‐injury.

Supercooling sperm in liquid nitrogen vapour is a feasible and economic technique for the practical production. The study aimed to reveal the negative effects of this rapid freezing and thawing processes on Taihang black goat spermatozoa and to find out the changing of spermatozoa motility and ultrastructure by using CASA and TEM. Qualified semen samples, which collected from twenty Chinese Taihang black goats using artificial vagina were pooled and investigated the kinematics parameters and ultrastructural morphology. The results showed that freezing–thawing caused a significant reduction in the spermatozoon total motility (P < 0.001), in rapid and medium cell numbers (P < 0.001) and motility parameters (VAP, VSL, VCL, ALH and BCF) (P < 0.01). Immotile spermatozoa number was increased significantly after freezing–thawing (P < 0.001). In the ultrastructural analysis, the shape with a sperm nucleus characterized by ruptures, bend and deformity was observed. The plasma membranes were broken, and nucleoplasm erupted. The mitochondria in the middle piece were disturbed by partial absence or additional accumulations. Swelling, coiling, vacuolization and structural disorganization of mitochondria were also observed. In conclusion, Freezing–thawing procedure has a detrimental effect on motility, membrane integrity and mitochondria of goat spermatozoa. Transmission electron microscopy provides an intuitive observation to investigate deformity spermatozoa.