Equine Blastocysts Research Articles

Storage and international transport of horse embryos in liquid nitrogen

SummaryThree different experiments were conducted in which horse embryos were frozen in liquid nitrogen, thawed and transferred surgically to synchronised recipient mares in two countries. In Experiment 1, out of 14 embryos transferred via mid ventral laparotomy, two established normal pregnancies, of which one continued to full term with the birth of a healthy colt foal. In Experiment 2, one of two embryos resulted in a normal conceptus. In Experiment 3, all the transfers were carried out via flank laparotomy and none of the recipients became pregnant. The results from Experiments 1 and 2 indicate that early unexpanded equine blastocysts tolerate cryopreservation better than larger expanded blastocysts. Some other factors associated with the transfer technique, unrelated to the viability of the frozen thawed embryos, are thought to have played a significant role in the failure to achieve any pregnancies in Experiment 3.

Antagonistic effect of LH on FSH-induced superovulation in cattle

Equine embryo transfers have increased dramatically in the past decade, but in spite of the advantages of cryopreservation of equine embryos, this technology has not increased proportionally. Lack of a superovulation protocol for mares and the inability to freeze embryos >300 μm have been the limiting factors impeding equine embryo cryopreservation. Data from both controlled laboratory settings and commercial embryo transfer facilities have shown that small embryos can be slow cooled or vitrified and, after thawing and transfer, provide pregnancy rates of 50%–70% similar to that obtained with bovine embryos. In contrast, studies have shown that embryos >300 are damaged more during slow cooling or vitrification than those <300 μm and result in low pregnancy rates after transfer. The presence of the acellular capsule in the equine blastocyst and the large volume of blastocoele fluid were thought to be the major reason for poor survival of cryopreserved large equine embryos. However, deflating the embryo before freezing has been shown to improve the survival of cryopreserved large equine embryos dramatically. Unfortunately, this must be done using very expensive equipment. Developments that could improve the success of equine embryo cryopreservation are as follows: having hormones available for superovulation, a means of hastening the embryo into the mare's uterus to consistently collect <300 μm embryos, or the development of a simple means of collapsing embryos >300 μm.

Influence of day of collection on recovery rate in mature cycling mares

Equine embryo transfers have increased dramatically in the past decade, but in spite of the advantages of cryopreservation of equine embryos, this technology has not increased proportionally. Lack of a superovulation protocol for mares and the inability to freeze embryos >300 μm have been the limiting factors impeding equine embryo cryopreservation. Data from both controlled laboratory settings and commercial embryo transfer facilities have shown that small embryos can be slow cooled or vitrified and, after thawing and transfer, provide pregnancy rates of 50%–70% similar to that obtained with bovine embryos. In contrast, studies have shown that embryos >300 are damaged more during slow cooling or vitrification than those <300 μm and result in low pregnancy rates after transfer. The presence of the acellular capsule in the equine blastocyst and the large volume of blastocoele fluid were thought to be the major reason for poor survival of cryopreserved large equine embryos. However, deflating the embryo before freezing has been shown to improve the survival of cryopreserved large equine embryos dramatically. Unfortunately, this must be done using very expensive equipment. Developments that could improve the success of equine embryo cryopreservation are as follows: having hormones available for superovulation, a means of hastening the embryo into the mare's uterus to consistently collect <300 μm embryos, or the development of a simple means of collapsing embryos >300 μm.