Pregnancy Rates to Fixed Embryo Transfer of Vitrified IVP Bos indicus, Bos taurus or Bos indicus × Bos taurus Embryos.

The pregnancy rates obtained after the transfer of cryopreserved in vitro-produced (IVP) embryos are usually low and/or inconsistent. The objective of this study was to evaluate the pregnancy rates of Holstein, Gyr and Holstein × Gyr cattle after the transfer of vitrified IVP embryos produced with X-sorted sperm. Seventy-two Gyr and 703 Holstein females were subjected to ovum pickup (OPU) sessions, followed by in vitro embryo production using semen from sires of the same breeds. Embryos (1636 Holstein, 241 Gyr and 1515 Holstein × Gyr) were exposed to forskolin for 48 h prior to vitrification. The pregnancy rate achieved with Gyr dam and sire was 46.1%, which was similar (p = 0.11) to that of Holstein dam and Gyr sire (40.3%). Crossing Gyr dams with Holstein sires resulted in a pregnancy rate of 38.9% and did not differ (p = 0.58) from the pregnancy rate obtained with the cross between Holstein dams and Gyr sires. The rate obtained with Holstein dam and sire was 32.5%. The average pregnancy rate was 36.6%, and no difference was found in the proportion of female foetuses (88.8%, in average) among breeds (p > 0.05). In conclusion, transfer of cryopreserved X-sorted embryos represents an interesting choice for dairy cattle. Despite the small differences between pregnancy rates, we highlight the efficiency of this strategy for all of the racial groups studied.

Effects of oocytes exposure to bovine diarrhea viruses BVDV-1, BVDV-2 and Hobi-like virus on in vitro-produced bovine embryo development and viral infection.

As production of in vitro (IVP) bovine embryos steadily increases, the sanitary risk associated with IVP embryos remains a concern. One of the greatest concerns is how BVDV may be transmitted through IVP embryos. The objective of this study was to evaluate the effects caused by BVDV-1, BVDV-2 and Hobi-like virus exposure during in vitro maturation on embryo development and viral infection. Abittior-derived oocytes were randomly assigned for in vitro maturation with serial concentrations of BVDV-1 (3.12 × 102 - 2.50 × 103 TCID50/100 µL), BVDV-2 (6.25 × 101 - 5.20 × 102 TCID50/100 µL) or Hobi-like virus (1.90 × 102 - 1.58 × 103 TCID50/100 µL) for 22-24 h. After maturation, oocytes were fertilized and embryo cultured following standard in vitro procedures. Embryo development was evaluated and percentage of respective, positive BVDV degenerated and viable embryos were evaluated by RT-qPCR. No concentration of BVDV-1 altered embryo development as measured by cleavage and blastocyst rates, compared to negative control group. However 100% of degenerated embryos and 50-100% of viable embryos tested positive for BVDV-1, depending on the viral concentration. BVDV-2 exposed oocytes had higher cleavage rates than the negative control group (60.2-64.1% vs 49.8%; P = 0.003-0.032). However, no difference was detected for blastocyst rates. In aadition, 100% of degenerated embryos and 20-50% of viable embryos tested positive for BVDV-2. Hobi-like virus treated oocytes had reduced cleavage rates for the three highest viral concentrations (33.3-38.0% vs 49.8% for negative controls; P ≤ 0.001-0.014). Blastocyst rates were only reduced in the 7.9 × 102 Hobi-like virus concentration (6.9 ± 0.9% vs 15.1 ± 1.6%; P = 0.009), when calculated by oocyte number. 50-80% of degenerated embryos tested positive for Hobi-like virus. No viable embryos from the Hobi-like virus treated oocytes tested positive. These results suggest that IVP embryos from BVDV-1 and -2 infected oocytes develop normally, but carry the virus. However, Hobi-like virus infected oocytes had reduced cleavage and cause pre-implantation embryo loss, but viable embryos did not carry the virus.