LAUSR

In this study, the quality of frozen bull semen was evaluated with the proAKAP4 level test. Sixty straws of frozen bull semen from various batches (n = 30) belonging to six bulls were used in the current study. The frozen bull semen samples were analysed in terms of proAKAP4 levels, sperm morphology and sperm movement parameters at hour 0 and hour 3 after thawing. The semen samples were divided into three groups according to the proAKAP4 levels: low concentration (<25 ng/10x106 spermatozoa), moderate concentration (25 to 39 ng/10x106 spermatozoa) and high concentration (≥40 ng/10x106 spermatozoa). A positive correlation was found between the proAKAP4 level and total motility (TM3), progressive motility (PM3), VSL3 and VCL3 values obtained after the third‐hour thermoresistance test (p < .05). There was a negative correlation between the percentage of sperm abnormal tail and the proAKAP4 level (p < .01). In addition, it was observed that the semen samples with proAKAP4 concentrations of 25 ng/106 spermatozoa and higher preserved the TM3 and PM3 motility characteristics. In conclusion, the proAKAP4 has the potential to become a biomarker protein to evaluate in the quality analysis of frozen‐thawed semen.