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  Discussion on Ovum Freezing
Author Message
Member:
jolie

Posted on Wednesday, Nov 10, 2010 - 11:09 am:

Dr. O

Do you know if it is possible to freeze unfertilized ovum. I have an ill mare who I would like to breed but can't afford embryo transplant at this time. I can't find any information regarding equine ovum.

Thank you for your time.

Jolie
Moderator:
DrO

Posted on Thursday, Nov 11, 2010 - 8:15 am:

Hello Jolie,
Yes it almost for sure is possible but as of yet dependable techniques have not been developed. This is the latest I can find on cryopreservation of equine oocytes:
Mol Reprod Dev. 2006 May;73(5):627-37.
Effect of maturation stage at cryopreservation on post-thaw cytoskeleton quality and fertilizability of equine oocytes.

Tharasanit T, Colenbrander B, Stout TA.
Faculty of Veterinary Medicine, Department of Equine Sciences, Utrecht University, Yalelaan, Utrecht, The Netherlands.

Abstract
Oocyte cryopreservation is a potentially valuable technique for salvaging the germ-line when a valuable mare dies, but facilities for in vitro embryo production or oocyte transfer are not immediately available. This study examined the influence of maturation stage and freezing technique on the cryopreservability of equine oocytes. Cumulus oocyte complexes were frozen at the immature stage (GV) or after maturation in vitro for 30 hr (MII), using either conventional slow freezing (CF) or open pulled straw vitrification (OPS); cryoprotectant-exposed and untreated nonfrozen oocytes served as controls. After thawing, GV oocytes were matured in vitro, and MII oocytes were incubated for 0 or 6 hr, before staining to examine meiotic spindle quality by confocal microscopy. To assess fertilizability, CF MII oocytes were subjected to intracytoplasmic sperm injection (ICSI) and cultured in vitro. At 12, 24, and 48 hr after ICSI, injected oocytes were fixed to examine their progression through fertilization. Both maturation stage and freezing technique affected oocyte survival. The meiosis resumption rate was higher for OPS than CF for GV oocytes (28% vs. 1.2%; P < 0.05), but still much lower than for controls (66%). Cryopreserving oocytes at either stage induced meiotic spindle disruption (37%-67% normal spindles vs. 99% in controls; P < 0.05). Among frozen oocytes, however, spindle quality was best for oocytes frozen by CF at the MII stage and incubated for 6 hr post-thaw (67% normal); since this combination of cryopreservation/IVM yielded the highest proportion of oocytes reaching MII with a normal spindle (35% compared to <20% for other groups), it was used when examining the effects of cryopreservation on fertilizability. In this respect, the rate of normal fertilization for CF MII oocytes after ICSI was much lower than for controls (total oocyte activation rate, 26% vs. 56%; cleavage rate at 48 hr, 8% vs. 42%: P < 0.05). Thus, although IVM followed by CF yields a respectable percentage of normal-looking MII oocytes (35%), their ability to support fertilization is severely compromised.

If you wish to pursue this I would contact a University or equine veterinary hospital that specializes in reproduction.
DrO
Member:
jolie

Posted on Thursday, Nov 11, 2010 - 9:16 am:

Thank you so much for the information Dr. O.
Member:
jhyrick

Posted on Thursday, Nov 11, 2010 - 10:20 am:

There is a woman vet at Colorado State University Equine Repro that is doing many things with mares that need to be euthanized. If the ovaries are harvested from the mare within a certain time period, they are later able to use the ovums and obtain some viable embryo's. I know this is not the case with your mare, but if they can do that at CSU, I bet they'll have other good options for you. Paula.Moffett@ColoState.EDU has been involved at CSU for many years and has helped direct me to the proper veterinarians at their locations. I would suggest contacting her. Best of luck.
Member:
jolie

Posted on Thursday, Nov 11, 2010 - 11:35 am:

Thank you so much for the info. We are not sure she will make it through our winter. She is the last of the line I have been breeding for over 20 years. Would really like a foal out of her, however as always money is the issue.

Thanks again!
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