In this study, motion characteristics of spermatozoa was assessed by computer assisted semen analyser (CASA) for evaluating fertility potential of Sahiwal bulls. Twelve bulls were selected and grouped into two on the basis of age (AGI < 50 months old; AGII > 50 months old) and scrotal circumferences (SCI < 33 cm; SCII > 33 cm). The following CASA parameters i.e., velocity average path (VAP, μm/s), velocity straight line (VSL, μm/s), velocity curvilinear (VCL, μm/s), amplitude of lateral head displacement (ALH, μm), motility (%)(the percentage motile cells of the total) and straightness (STR) were recorded. Results of the study revealed that there is no significant different (p>0.05) in progressive motility either in age or Sc groups of bulls. However, significantly (p<0.05) higher mean post thaw motility was observed after 24 h cryopreservation for the younger (76.40±3.07) than the older (65.00±3.50) bulls and for larger SC than smaller SC bulls (65.56±3.78 vs. 56.56±3.78, p<0.05). Similar trends observed at 0 h after freezing were not significantly different (p>0.05) for both age and SC groups. In most motion characteristics especially in motility and linearity of the motion, younger bulls and bulls with larger SC performed better than older bulls and bulls with smaller SC indicating the possibility of selecting bulls at an early age on the basis of testis size to save the money, space and time which otherwise spent on rearing such inferior bulls. This study also clearly indicated that CASA is a good supplementation to aid for selection of breeding bulls.
Key words: Sahiwal bull, computer-assisted semen analysis (CASA) parameters, spermatozoa motion characteristics.
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