https://www.selleckchem.com/products/bay-11-7082-bay-11-7821.html Sub-fertility is a major problem in crossbred bulls. Identification of subtle differences in the quality of cryopreserved spermatozoa among bulls belonging to different fertility rankings would help determine the latent fertility of semen before their use at field conditions. In the present study, we assessed the status of tyrosine phosphorylation, membrane integrity and acrosome reaction of cryopreserved spermatozoa in crossbred bulls (n = 22) with different levels of field fertility and assessed their relationship with fertility. Bulls were categorized into above-average (n = 4), average (n = 14) and below-average (n = 4) based on their different field fertility rates. The progressive sperm motility was significantly (P less then 0.05) higher in above-average fertile bulls compared to either average or below-average fertile bulls whereas sperm membrane integrity and acrosomal reaction status did not differ among the three groups. The proportion of live tyrosine-phosphorylated spermatozoa were significantly (P less then 0.05) higher in below-average and average fertile bulls compared to above-average bulls. Immunolocalization of protein tyrosine phosphorylation in spermatozoa revealed that the proportion of spermatozoa showing tyrosine phosphorylation at acrosome and post-acrosomal area (APA) and at acrosome, post-acrosome and tail (APAT) were significantly (P less then 0.05) higher in below-average fertile bulls than other groups. The APA pattern (r = -0.605; P less then 0.01) and APAT (r = 0.507; P less then 0.05) pattern were significantly and negatively correlated with bull fertility. It was concluded that the proportion of live tyrosine-phosphorylated spermatozoa in cryopreserved semen was negatively related to bull fertility. The presence of serum in embryo culture medium has been implicated for increased embryo's sensitivity to cryopreservation, compromised viability, abnormal embryo and fetal