Risk of Transmission of Bovine Leukosis Virus (BLV) Using Semen from Seropositive Bulls in In Vitro Produced Embryos

Abstract

Bovine Leukosis Virus (BLV) is a pathogen that affects the bovine immune system and leads to lymphosarcoma, leukemia, decreased milk production, and increased culling rates in cattle. The main transmission route between cattle is transfer of infected leukocytes from blood. Several farm practices, such as dehorning, rectal palpation, and vaccination can lead to pathogen transfer between animals that ultimately leads to high percentages of infected individuals within herds. This high percentage of infected animals restricts the trade of cattle on a global scale. Due to international trade laws and biosecurity concerns, semen from a BLV positive bulls is prohibited from sale between certain countries. The aim of this research was to study BLV transmission to embryos produced by in vitro fertilization (IVF) with semen from seropositive bulls. The first experiment examined the possible BLV transmission to embryos using seropositive bull semen in in vitro embryo production (IVP). The second experiment tested semen and medium for the presence of BLV using two different protocols for sperm selection: 1) Percoll discontinuous gradients and 2) Swim-Up. The results showed no virus detection in the samples and the embryos produced did not show presence of the virus. The same results were observed in the second experiment where no viral presence was observed in the semen or media samples after sperm selection. In conclusion, these data indicate the use of BLV seropositive bull semen for the production of in vitro fertilized embryos posed no statistically significant risk of transmitting BLV to the embryos.