Cryopreservation of oocytes by vitrification technique may contribute a lot in the field of reproductive biotechnology. The objectives of the present study were to evaluate the effectiveness of two cryo-devices for vitrification of immature oocytes of indigenous zebu cows. Slaughter house derived immature cumulus-oocyte-complexes (COCs) of cows were vitrified using 15% dimethyl sulphoxide (DMSO) as cryoprotective agent (CPA) with 0.5 mol sucrose in TCM 199 supplemented with 20% FBS. Vitrification of COCs was completed after immediate plunging of COCs loaded cryotop or French mini straw into the liquid nitrogen (LN2). Then the COCs containing cryotop or French mini straws were warmed in 0.25 mol sucrose and 20% FBS supplemented TCM 199 followed by in vitro culture in 50 μl droplets of bicarbonate buffered TCM 199 supplemented with 10% FBS, pyruvate, FSH and oestradiol for 24 hrs at 39°C with 5% CO2 in humidified air. After maturation culture, oocytes were denuded and examined under inverted microscope for presence of polar body as the indication of maturation. Denuded oocytes were also stained by whole mount technique using 1% orcein to examine the maturation by presence of MII chromosomes. The in vitro maturation rate was significantly (p<0.05) higher in oocytes vitrified and warmed using crytop (47.1±6.9%) than that of French mini straw (15.9±12.5%). Moreover, in vitro maturation rate was significantly (p<0.05) highe r in control oocytes (not vitrified) (84.5±14.2%) than that of vitrified oocytes. In conclusion, cryotop is better than French mini straw as cryo-device for vitrification of bovine immature oocytes

INTRODUCTION
 MATERIALS and METHODS
  1. Chemicals and media
  2. Collection of ovaries
  3. Collection of oocytes
  4. Selection of occytes for culture
  5. Vitrification and warming
  6. In vitro culture of oocytes for maturation
  7. Evaluation of oocytes for maturation
  8. Staining of oocyte
  9. Experimental approaches and statistical analysis
 RESULTS
 DISCUSSION
 ACKNOWLEDGEMENT
 REFERENCES

• Sk Mohiuddin Choudhury(Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh)
• Mohammad Musharraf Uddin Bhuiyan(Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh) Correspondence
• Mohammad Moshiur Rahman(Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh)
• Md. Masudur Rahman(Veterinary Surgeon, Department of Livestock Services, Dhaka, Bangladesh)
• Md. Newaz Sharif(Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh)
• Jayonta Bhattacharjee(Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh)
• Farida Yeasmin Bari(Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh)
• Nasrin Sultana Juyena(Department of Surgery and Obstetrics, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh)