Effect of artificial heat stress on Belgian blue bull’s semen quality after thawing

This study was aimed to evaluate whether high ambient temperature (heat stress, HS) can affect sperm quality parameters in Belgian blue bulls. For this purpose, semen samples were collected from three healthy mature Belgian blue bulls which were located in a breeding company under uniform feeding and management conditions. After semen collection, and the primary evaluations, the ejaculates with more than 60 percent total motility were subjected to the freezing process. After thawing the samples were used to assess the motion parameters, morphological abnormalities, acrosome integrity, chromatin condensation, viability, hydrogen peroxide (H2O2) and hydroxyl ion production. The results indicated that total and progressive motility and straight-line velocity were lower in the HS group compared to the control (P≤0.05), moreover, the generation of H2O2, hydroxyl ions, percentage of aberrant chromatin condensation, total morphological abnormal sperm cells, spermatozoa with bent tails and proximal protoplasmic droplets were higher in the HS compared to the control (P≤0.05) while the percentage pf damaged acrosome was not differ between HS and control (P≥0.05). In conclusion, these findings show that elevated ambient temperature can decrease the quality of frozen-thawed bull spermatozoa may leading to a lower fertility rate.