Original Research Evaluation of Sperm Characteristics in Caspian Stallions Using Computer-Assisted Sperm Analysis Alireza Rezagholizadeh, Faramarz Gharagozlou, Amir Niasari-Naslaji * , Vahid Akbarinejad, Soudeh Ziapour Department of Theriogenology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran article info Article history: Received 2 December 2014 Received in revised form 25 January 2015 Accepted 2 February 2015 Available online xxxx Keywords: Caspian stallion Seminal parameter CASA abstract Knowledge of reference values for seminal parameters is a prerequisite for stallion breeding management. The present study was conducted to determine seminal charac- teristics of Caspian stallions. Fifty-two ejaculates were collected from seven healthy Cas- pian 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  10 6 sperm/mL, 87.06  7.62%, 44.54  14.65%, 189.33  30.64 mm/s, 82.88  11.49 mm/s, 113.52  13.02 mm/s, 71.20  8.38%, 45.57  9.12%, 6.68  1.05 mm, 34.15  9.37 Hz, 61.77  4.85%, and 4.70  1.25 mm 2 , 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. Ó 2015 Elsevier Inc. All rights reserved. 1. Introduction The Caspian miniature horse is one of the oldest horse breeds in the world, which was originated from the southern coast of Caspian Sea and northern areas of Alborz Mountains, and is believed to be the first horse to be used in the Middle East [1]. Interestingly, it was rediscovered in 1965 [2]. This breed is considered critically endangered with the registered population of approximately 150 horses in Iran [2]. This small population resulted in inbreeding [3,4], which in turn could adversely impact fertility in this breed [5–7]. Therefore, the limited population of Caspian horses requires intensive attention in terms of breeding management. Undoubtedly, reproductive management of stallions would be one of the cornerstones of breeding management programs for preservation of Caspian horses. In this regard, the variation in sperm characteristics of stallions needs to be assessed to define the standards for selection of a stallion based on his sperm characteristics [8]. The present study was conducted to determine the seminal characteristics of Caspian stallions including computer-assisted sperm analysis (CASA), which provides the opportunity to analyze several seminal parameters * Corresponding author at: Amir Niasari-Naslaji, Department of Ther- iogenology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. E-mail address: niasari@ut.ac.ir (A. Niasari-Naslaji). Contents lists available at ScienceDirect Journal of Equine Veterinary Science journal homepage: www.j-evs.com 0737-0806/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jevs.2015.02.003 Journal of Equine Veterinary Science xx (2015) 1–5