Evaluation of Sperm Characteristics in Caspian Stallions Using Computer-Assisted Sperm Analysis

•The present study provided some seminal parameters of Caspian stallions.•There is individual variation among Caspian stallions for seminal parameters.•The shape of sperm head is correlated with sperm motility in stallion.

Knowledge of reference values for seminal parameters is a prerequisite for stallion breeding management. The present study was conducted to determine seminal characteristics of Caspian stallions. Fifty-two ejaculates were collected from seven healthy Caspian stallions (age: 8–16 years old) during the breeding season. Thirty-five ejaculates (five ejaculates per stallion) were used for calculation of mean values of seminal characteristics. After evaluation of pH and osmolality in initial collections, the semen was analyzed for volume, motility, and some morphometric parameters using computer-assisted sperm analysis (CASA). The overall mean ± standard deviation values for volume of ejaculate, concentration, total motility, progressive motility (PMS), curvilinear velocity (VCL), straight-line velocity (VSL), average path velocity, straightness (STR), linearity (LIN), amplitude of lateral head displacement, beat cross frequency, elongation, and area were 19.89 ± 10.65 mL, 234.82 ± 143.14 × 106 sperm/mL, 87.06 ± 7.62%, 44.54 ± 14.65%, 189.33 ± 30.64 μm/s, 82.88 ± 11.49 μm/s, 113.52 ± 13.02 μm/s, 71.20 ± 8.38%, 45.57 ± 9.12%, 6.68 ± 1.05 μm, 34.15 ± 9.37 Hz, 61.77 ± 4.85%, and 4.70 ± 1.25 μm2, respectively. There were significant differences among stallions in sperm velocity and head-related parameters (P < .05). Sperms with greater elongation and lower area had greater PMS, VSL, STR and LIN (P < .05), and lower VCL (P < .05). In conclusion, the present study provided the mean values for seminal parameters of Caspian stallions. Additionally, the results revealed that sperms with more elongated heads had greater straight velocity and were, in turn, more progressive.