Quality assessment of frozen bull semen with the precursor A‐kinase anchor protein 4 biomarker

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/10x10 6 spermatozoa), moderate concentration (25 to 39 ng/10x10 6 spermatozoa) and high concentration (≥40 ng/10x10 6 spermatozoa). A positive correlation was found between the proAKAP4 level and total motility (TM 3 ), progressive motility (PM 3 ), VSL 3 and VCL 3 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/10 6 spermatozoa and higher preserved the TM 3 and PM 3 motility characteristics. In conclusion, the proAKAP4 has the potential to become a biomarker protein to evaluate in the quality analysis of frozen‐thawed semen.