For comparison, in the same study, when noncytopathic biotypes of BVDV type 2 was used it caused high embryonic mortality and 15% of the recipients seroconverted with only one healthy calf born [21]. In another study, when heifers were inoculated in utero with
approximately 878 TCID50/mL of BVDV strain SD-1 concurrent with transfer of “clean” embryos, all recipients seroconverted and infection caused high embryonic
mortality. Only one dead fetus at Day 60 after ET was detected [26]. From this observation it is clear that various BVDV strains might differ not only in their affinity for the zona pellucida [40] of in vivo- and in vitro-fertilized embryos, but also in their virucidal effect on the viability of developing embryos.