Bulls play a major role in BVDV transmission. Since an infection with this kind of cattle disease can affect the quality of the semen, the performance of breeding bulls can suffer considerably. BVDV infection can reduce semen quality significantly and therefore poses a threat to the production targets of the herd. When it comes to PI bulls, the semen quality is almost always poor. Some bulls may still sire calves, but most of the time they are infertile.