Comparison of two different methods for the vitrification of hatched blastocysts from the dromedary camel (Camelus dromedarius)
J. A. Skidmore A C , M. Billah A and N. M. Loskutoff BA Camel Reproduction Centre, PO Box 11808, Dubai, United Arab Emirates.
B Centre for Conservation and Research, Henry Doorly Zoo, Omaha, NE 68107, USA.
C Corresponding author. Email: luluskid@emirates.net.ae
Reproduction, Fertility and Development 17(5) 523-527 https://doi.org/10.1071/RD04082
Submitted: 30 July 2004 Accepted: 23 March 2004 Published: 2 May 2005
Abstract
The uteri of 32 donor camels were flushed non-surgically on Day 6, 7 or 8 after ovulation and a total of 184 embryos was recovered. Sixty Day 6 embryos and 61 Day 7 embryos were vitrified or frozen ultrarapidly using open pulled straws and a modified version of the Vajta protocol. These embryos were subjected to concentrations of either 10% and 20% or 20% and 40% ethanediol as the cryoprotectant before being loaded into open pulled straws (OPS) and plunged into liquid nitrogen. All embryos were subsequently thawed and rehydrated either directly into holding media or into holding media containing 0.2 m sucrose and were incubated for 5 or 10 min before being transferred to holding media before transfer to recipients. Although the survival rate of the embryos immediately after thawing was high (OPS 20%/40% ethanediol resulted in 97% and 100% survival for Day 6 and Day 7 embryos, respectively; OPS 10%/20% ethanediol resulted in 90% and 70% survival for Day 6 and Day 7 embryos, respectively), after 2 h in culture, survival rates had decreased to 46% and 53% for Day 6 and Day 7 embryos, respectively, using OPS 10%/20% and 53% and 63% for Day 6 and Day 7 embryos, respectively, using OPS 20%/40%; however, none of the embryos transferred resulted in a viable fetus. A further 63 embryos (Day 6: n = 31; Day 7: n = 16; Day 8: n = 16) were subsequently exposed to vitrification solution (20% glycerol + 20% ethylene glycol + 0.3 m sucrose + 0.375 m glucose + 3% polyethylene glycol) in three steps and after loading into 0.25 mL straws were plunged into liquid nitrogen. However, a much greater percentage of the Day 7 and Day 8 embryos (43.8% and 81.2% respectively) were fractured or torn after warming and none of the 12 intact embryos transferred resulted in a pregnancy. Better survival rates immediately after thawing and rehydration were obtained with the smaller Day 6 embryos (94%), which resulted in a total of eight fetuses from the 21 embryos transferred.
Extra keyword: cryopreservation.
Acknowledgments
The authors thank Dr James Wood from the Animal Health Trust, Newmarket, for his valuable assistance with the statistical analyses and Dr E. Crichton from Henry Doorly Zoo, Omaha, for her valuable assistance with the preparation of the manuscript. The study was kindly sponsored by H. H. General Shaikh Mohammed bin Rashid Al Maktoum, Crown Prince of Dubai.
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