37 Present address: 1 Senior Scientist (haidermeraj@ rediffmail.com), 2 Young Professional II (papiyasinha10@ gmail.com), 3 Junior Research Fellow (samudrabikash06@ gmail.com), 4 Scientist (perumalponraj@gmail.com); Animal Reproduction Division. Till now, assessment of semen quality (i.e. sperm concentration, motility, and morphology) was based on subjective microscopic techniques (Rijselaere et al. 2005). Yet, the inconsistency of results obtained with the use of conventional methods of semen evaluation is high (Iguer– ouada et al. 2001). Computer-assisted sperm analysis (CASA) system allows an accurate, repeatable, reliable and objective assessment of different semen parameters such as concentration, total and progressive motility, and different velocity parameters (Rijselaere et al. 2012) based on the measurement of individual sperm cells. Recent reports suggested that CASA does not only measure the proportion of motile spermatozoa but also measures other sperm motion parameters derived from individual sperm cells and it has more predictive power on fertility potential of semen ejaculates (Mortimer 1994). Spermatozoa kinematic parameters such as forward progressive motility (PFM), straight line velocity (VSL), curvilinear velocity (VCL), amplitude of lateral head displacement (ALH), and linearity (LIN) were positively correlated with bull fertility (Perumal et al. 2011). A spermatozoon has significantly higher VCL and ALH, indicating that there is major bending of the mid piece and large amplitude of lateral head displacement. This signifies the hyperactivation of the spermatozoa. Hyperactivation in turn implies high energy state of the spermatozoa, which is essential for sperm penetration through cervical mucus, zona pellucida, fuse with the oocytes, and successful fertilization (Aitken et al. 1985). Study of CASA parameters was reported in domestic animal species such as cattle (Perumal et al. 2011). Hence, the aim of this study was to determine the sperm motile parameters of mithun semen using a computer assisted sperm analyser. MATERIALS AND METHODS Mithun semen ejaculates (50) were collected during March 2015 to March 2016. Semen samples were collected through rectal message method from adult healthy mithun, maintained in the mithun farm of National Research Centre on Mithun (ICAR), Jharnapani, Nagaland, India with age ranging between 3–5 years and body weight approximately 300–450 kg. During the study, the animals were handled as per regulations of Institutional Animals Ethics Committee. Immediately after collection, the semen samples were kept in a water bath at 37°C and transported to the laboratory in an insulated flask maintaining 37°C for routine analysis (volume, consistency, colour and pH) within an hour. After the preliminary evaluations, ejaculates were subjected to the initial dilution with pre-warmed (37°C) tris-citrate extender. Semen samples were assayed using CASA (Hamilton Thorne Sperm Analyser, IVOS 11; HTM-IVOS, Version 10.8, Hamilton Thorne Research, Beverly, MA, USA) equipment. This CASA system is equipped with a phase-contrast microscope, camera, minitherm heating stage and image digitizer attached with a computer. The settings for CASA system are shown in Table 1. Diluted semen (2 μl) was mounted in a disposable Leja counting chamber Indian Journal of Animal Sciences 87 (3): 293–296, March 2017/Article Study on sperm motility and velocity parameters of freshly collected mithun semen through computer-assisted sperm analyser (CASA) M H KHAN 1 , PAPIYA SINHA 2 , S B HAZARIKA 3 and P PERUMAL 4 National Research Centre on Mithun, Jharnapani, Medziphema, Nagaland 797 106 India Received: 3 May 2016; Accepted: 21August 2016 ABSTRACT The objective of this study was to evaluate the quality of mithun semen by computer assisted sperm analysis (CASA). Ejaculates (50) were analysed by CASA. Semen motility was evaluated for kinetics parameters. The percentage of total motile and progressive motile spermatozoa were determined. Several velocities parameters were also determined viz., average path velocity (VAP, μm/s), track speed (VCL, μm/s), progressive velocity (VSL, μm/s), lateral amplitude (ALH), beat frequency (BCF, Hz), straightness (%), elongation (%), linearity (%), and area (μm sq). The result revealed a strong positive correlation between various CASA parameters (PMOT- VAP, PMOT- VSL, VAP-VSL, VAP-ALH, VSL-ALH, STR-LIN).The present study confirmed the usefulness of CASA for a quick and objective analysis of sperm concentration, motility and other velocity parameters. Key words: CASA, Mithun, Sperm motility, Velocity parameters https://doi.org/10.56093/ijans.v87i3.68849