Bovine Leukemia ProVirus: Evidence of Presence of Part of Gag Gene in Seminal Plasma of Naturally Infected Bulls It is of critical importance to understand the modalities of BLV presence in semen, especially with regard to artificial insemination (AI). Presence of bovine leukemia provirus was demonstrated in fresh and frozen semen samples by researchers. In this study paired blood and semen samples from 45 bulls were assessed for the presence of part of gag gene and antibodies to BLV in blood, semen and cell-free fraction of the semen (seminal plasma). Proviral DNA was detected in 5 out of 45 seminal plasma samples. PCR products were sequenced and submitted to gene bank. This data strongly suggested that seminal plasma of seropositive bulls can be positive in PCR.