Computer assisted sperm analysis of fresh and frozen-thawed HF x Kankrej (F₁) bulls semen and their interrelationship

A total of 30 good quality semen ejaculates from 5 mature bulls of HF x Kankrej (F₁) breed were studied for sperm motility and velocity parameters of fresh and frozen-thawed spermatozoa using computer assisted sperm analyzer (CASA). The ejaculates immediately after collection in AV were assessed by CASA for fresh sperm motility and velocity parameters. A part of each ejaculate cryopreserved at −196°C in LN₂ using standard Tris-citric acid-fructose-yolk-glycerol extender was thawed and assessed for post-thaw analysis of motility and velocity traits on CASA using via-dent stain. The mean values of motile and progressively motile spermatozoa observed in fresh semen (74.73±1.71 and 51.57±2.61%) were highly significantly (P<0.01) reduced (50.80±1.36 and 30.23±1.16%, respectively) in post-thawed semen. The Average Path Velocity (VAP), Straight Line Velocity (VSL) and Curvilinear velocity (VCL) of spermatozoa noted in fresh semen were also reduced significantly (P<0.01) in frozen-thawed semen. Amplitude of Lateral Head displacement (ALH, m) and its Elongation (%) were increased, while Beat-Cross Frequency (BCF, Hz), Straightness (%), Linearity (%) and sperm area (m²) were decreased in post-thawed sperms. The proportion of rapidly motile sperm was significantly reduced and that of slow motile and static sperm increased in post-thawed semen, suggesting cryodamage to the spermatozoa. Most of the CASA traits of fresh and frozen-thawed spermatozoa were significantly and positively interrelated. Thus, CASA appeared to be the fast, accurate and precise means of qualitative evaluation of the fresh and frozen-thawed bull semen.