Embryo technologies in the horse.
Abstract: Recent studies demonstrated that zwitterionic buffers could be used for satisfactory storage of equine embryos at 5 degrees C. The success of freezing embryos is dependent upon size and stage of development. Morulae and blastocysts <300 microm can be slowly cooled or vitrified with acceptable pregnancy rates after transfer. The majority of equine embryos are collected from single ovulating mares, as there is no commercially available product for superovulation in equine. However, pituitary extract, rich in FSH, can be used to increase embryo recovery three- to four-fold. Similar to human medicine, assisted reproductive techniques have been developed for the older, subfertile mare. Transfer of in vivo-matured oocytes from young, healthy mares into a recipient's oviduct results in a 70-80% pregnancy rate compared with a 30-40% pregnancy rate when the oocytes are from older, subfertile mares. This procedure can also be used to evaluate in vitro maturation systems. In vitro production of embryos is still quite difficult in the horse. However, intracytoplasmic sperm injection (ICSI) has been used to produce several foals. Cleavage rates of 60% and blastocyst rates of 30% have been reported after ICSI of in vitro-matured oocytes. Gamete intrafallopian tube transfer (GIFT) is a possible treatment for subfertile stallions. Transfer of in vivo-matured oocytes with 200,000 sperm into the oviduct of normal mares resulted in a pregnancy rate of 55-82%. Oocyte freezing is a technique that has proven difficult in most species. However, equine oocytes vitrified in a solution of ethylene glycol, DMSO, and Ficoll and loaded onto a cryoloop resulted in three pregnancies of 26 transfers and two live foals produced. Production of a cloned horse appears to be likely, as several cloned pregnancies have recently been produced.
Copyright 2002 Published by Elsevier Science Inc.
Publication Date: 2002-12-25 PubMed ID: 12499026DOI: 10.1016/s0093-691x(02)01268-2Google Scholar: Lookup
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Summary
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The research paper discusses various techniques to enhance reproduction rates in horses. It particularly highlights methods like using zwitterionic buffers for embryo storage, slow cooling of small stake embryo, use of pituitary extract for superovulation, and transfer of in vivo-matured oocytes for better pregnancy rates even in older mares. Additionally, the practicality of intracytoplasmic sperm injection (ICSI), gamete intrafallopian tube transfer (GIFT), oocyte freezing, and potential for cloning are also discussed.
Buffer Use for Embryo Storage
- Equine embryos can be successfully stored at 5 degrees C using buffers that are zwitterionic (having both positive and negative charges).
- The size and stage of development of embryos determine the success rate of freezing them—the smaller the size (<300 microm), the better the result.
Superovulation for Embryo Recovery
- Most equine embryos are collected from single ovulating mares, and there are no commercially available superovulation products in equine.
- Pituitary extract rich in FSH can be used for superovulation to increase embryo recovery by a factor of three to four.
Assisted Reproduction Techniques
- Similar to human medicine, assisted reproductive techniques are developed for older or subfertile horses.
- In vivo-matured oocytes from young, healthy mares transferred to a recipient’s oviduct result in a 70-80% pregnancy rate, much higher than the 30-40% rate of older, subfertile mares.
Use of Intracytoplasmic Sperm Injection (ICSI)
- In vitro embryo production is challenging in the horse, but ICSI has been successful in producing several foals.
- ICSI has reported a 60% cleavage rate and 30% blastocyst rate with in vitro-matured oocytes.
Cutting-Edge Techniques: GIFT and Cloning
- Gamete intrafallopian tube transfer (GIFT) could help with subfertile stallions. When in vivo-matured oocytes paired with 200,000 spermatozoa were transferred into the oviduct of normal mares, it resulted in a 55-82% pregnancy rate.
- Oocyte freezing, usually technically challenging, has shown promising results in horses when vitrified in a solution comprising ethylene glycol, DMSO, and Ficoll.
- The successful production of cloned horses appears likely as there have been instances of cloned equine pregnancies recently.
Cite This Article
APA
Squires EL, Carnevale EM, McCue PM, Bruemmer JE.
(2002).
Embryo technologies in the horse.
Theriogenology, 59(1), 151-170.
https://doi.org/10.1016/s0093-691x(02)01268-2 Publication
Researcher Affiliations
- Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, CO 80523, USA. esquires@cvmbs.colostate.edu
MeSH Terms
- Animals
- Cloning, Organism
- Cryopreservation
- Culture Techniques
- Embryo Transfer / veterinary
- Embryo, Mammalian / physiology
- Female
- Fertilization in Vitro / veterinary
- Gamete Intrafallopian Transfer / veterinary
- Horses / embryology
- Oocyte Donation / veterinary
- Pregnancy
- Reproductive Techniques, Assisted / veterinary
- Sperm Injections, Intracytoplasmic / veterinary
- Superovulation
- Tissue and Organ Harvesting
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