Fu et al. 2019 have recently identified the marker AKAP4 in the spermatozoa from fertile normozoospermic buffalos, bulls or swines.
They also stated that never found in the seminal fluids - Only in cells, spermatozoa.
Check out their last publication in Theriogenology journal.
They described AKAP4 being among the most important proteins in fertile water buffalos, as this was previously described in Holstein bulls by Peddinti et al. (2008), Singh et al. (2019) and Ruelle et al. (2019).