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Reproduction: gamete intrafallopian transfer

ISSN 2398-2977


Synonym(s): GIFT, Gamete intraviductal transfer

Introduction

  • Gamete intrafallopian transfer (GIFT) is the surgical deposition of a donor mare oocyte and spermatozoa into the fallopian tube (oviduct) of a recipient mare.
  • GIFT differs from oocyte transfer Reproduction: oocyte transfer. In oocyte transfer the donor mare oocyte is placed in the oviduct of a recipient mare, and the recipient is inseminated by deposition of semen into the uterus. Whereas, in GIFT both the oocyte and spermatozoa are placed directly into the recipient mare’s fallopian tube (oviduct) for in vivo fertilization, with subsequent embryonic and fetal development occurring in the recipient mare.

Uses

  • Oocyte donation Reproduction: oocyte collection followed by oocyte transfer Reproduction: oocyte transfer is a useful technique in obtaining pregnancies from mares whose subfertility is attributable to some cause other than poor oocyte quality.
  • However, oocyte donation and transfer is used in conjunction with conventional artificial insemination techniques, and its success therefore relies partly on the semen being of good quality.
  • Because GIFT involves the deposition of both oocyte and spermatozoa in the fallopian tube (oviduct) near the site of fertilization, sperm cells do not have to successfully navigate from the uterus, through the utero-tubal junction, into the fallopian tube (oviduct). GIFT is therefore a more useful technique than oocyte transfer alone when either the quality of the semen is poor, or sperm numbers are low (for example when only small quantities of either frozen semen or sex-sorted sperm cells are available).

Advantages

  • Provides a method of achieving pregnancies in cases of combined mare subfertility (due to a factor other than oocyte quality) and poor semen quality / limited sperm numbers.
  • This is useful since whereas in other species in vitro fertilization is often used to overcome such cases of combined female:male subfertility, in horses, in vitro fertilization is comparatively unsuccessful.
  • GIFT is useful in mares which suffer from post-mating induced endometritis due to poor clearance of uterine fluid.

Disadvantages

  • Very variable success rates.
  • Poor pregnancy rates associated with the use of chilled and frozen semen.

Technical problems

  • Problems with oocyte maturation and transfer Reproduction: oocyte transfer.
  • Need to process semen to remove seminal plasma, debris and contamination (see below) and to select fertile sperm (see below).
  • Lower success rates are currently achieved using chilled and frozen semen (which are likely to be used commonly in practice) than using freshly collected semen.

Alternative techniques

  • Intracytoplasmic sperm injection.

Requirements

Personnel

Veterinarian expertise

  • Expertise in mare and stallion reproduction.
  • Surgical expertise to complete intrafallopian transfer of gametes via standing flank laparotomy Abdomen: surgical approaches.

Anesthetist expertise

  • Sedation.
  • Provide local anesthesia for standing flank laparotomy.

Other involvement

Materials required

Minimum equipment

  • See Reproduction: oocyte transfer for materials needed for oocyte preparation and handling.
  • For sperm preparation, some means of separating the sperm cells from the seminal plasma, debris and contamination, and of selecting morphologically and motile semen (see below).

Minimum consumables

Other requirements

  • Stocks to restrain the mare for standing laparotomy.

Preparation

Pre-medication

  • Analgesia, eg flunixin meglumine Flunixin meglumine should be provided before the procedure starts.

Preparation of occyte

Preparation of semen

  • Because the sperm cells are being deposited directly into the fallopian tube (oviduct), the physiological mechanisms that normally occur in the uterus and at the utero-tubal junction for removing debris, seminal plasma and contaminants, and selecting morphologically normal and motile sperm cells are by-passed, and must be undertaken in the laboratory instead.
  • Generally, removal of seminal plasma, contaminants and debris is undertaken by centrifuging the ejaculate, removing the supernatant (which contains seminal plasma, contaminants and debris), and re-suspending the sperm cells in a semen extender. Selection of morphologically normal and motile sperm cells is most commonly achieved in horses using a ‘density gradient’, eg Percoll or ‘Equipure’ (see below).
  • The two processes of separating seminal plasma / debris / contaminants and selecting morphologically normal, motile cells, may occur:
    • At the same time if the first centrifugation is undertaken using a density gradient. Usually for freshly collected semen, or for chilled semen which has not been centrifuged as part of the chilling process.
    • Or as separate steps for chilled semen which has already been centrifuged once, and for frozen semen. In these instances, centrifugation using the density gradient is undertaken shortly before use of the semen. This will be after thawing for frozen semen.
  • Details of centrifugation techniques are provided in the references.
  • Briefly, the density gradient technique is based on the separation of spermatozoa into subpopulations with different specific gravities:
    • Semen is layered over the gradient, and the tubes are centrifuged.
    • The spermatozoa are separated based on motility and morphology, because most of the normal spermatozoa pass through the gradients, and accumulate in the sperm pellet at the bottom of the tube.
    • Most of the non-motile or morphologically abnormal spermatozoa, premature germ cells, other cells, and extender components get trapped at the interface between the gradients, or in one of the two gradients.
  • Exact details of final sperm treatment and re-suspension differ between authors, but ultimately a small aliquot of semen (2-5 x 105 motile sperm) is usually added to <200 μl of the holding media containing the oocyte(s) to be transferred, and drawn up into a polished glass pipette, shortly before the GIFT process.

Preparation of the mare

Restraint

  • Mares should be restrained in stocks for the GIFT procedure.
  • Mares should be sedated (usually with a combination of an Alpha-2 adrenoceptor stimulant, eg detomidine hydrochloride Detomidine hydrochloride and an opioid such as butorphanol Butorphanol.

Technique

Approach

Step 1 - Surgical preparation

Step 2 - Incise skin

  • A vertical skin incision, c 8-10 cm in length, is made midway between the last rib and tubar coxae.

Step 3 - Dissect muscle

  • The muscle layers are bluntly dissected.

Step 4 - Puncture peritoneum

  • The peritoneum is punctured.

Core procedure

Step 1 - Locate ovary

  • The ovary is manually located, gently moved to the incision site and partially exteriorized.
  • The contorted fallopian tube (oviduct) can usually be visualized on the surface of the ovary.

Step 2 - Locate oviduct

  • The external os of the fallopian tube (oviduct) is located within the funnel shaped infundibulum overlying the ovulation fossa.
  • The glass pipette containing the oocyte and sperm cells is gently advanced through the external os, 2-3 cm into the fallopian tube (oviduct).
  • The oocyte and 2-5 x105 motile sperm cells are deposited into the fallopian tube (oviduct).

Step 3 - Return ovary to abdominal cavity

Aftercare

Immediate Aftercare

Monitoring

  • Mares should be monitored for signs of pain and infection.

Analgesia

Antimicrobial therapy

  • Broad-spectrum antimicrobials should be provided for c 3-5 days after surgery.

Other medication

  • If an acyclic recipient has been used Reproduction: oocyte transfer, treatment with exogenous progestagens (altrenogest Altrenogest (Regumate) at 0.44 mg/kg/day PO) is necessary to provide adequate progesterone levels to allow normal embryonic development and pregnancy maintenance.
  • Theoretically, cycling recipient mares should produce a corpus luteum after aspiration of their own follicle. However, luteal function may have been disrupted by the removal of granulosa cells; many clinicians therefore supplement these mares with altrenogest Altrenogest nonetheless.

Potential complications

  • Pain.
  • Infection.

Long term Aftercare

Follow up

  • Ultrasound diagnosis of pregnancy can be performed 12-14 days after transfer.
  • Repeated examinations should be undertaken to detect early embryonic loss Abortion: early embryonic/fetal death.

Outcomes

Complications

  • Oviductal adhesions.
  • Risks of inadvertent fertilization of the recipient mare's oocyte in cyclic mares.

Reasons for treatment failure

  • Inadequate technical expertise.
  • Poor quality oocyte.
  • Poor quality or insufficient sperm.
GIFT is generally less successful than oocyte transfer plus conventional insemination if semen quality is acceptable, but may still provide a method of obtaining pregnancies where semen quality or quantity are limited.
  • Pregnancy rates following GIFT have shown to be significantly higher with use of fresh rather than chilled or frozen semen.

Further Reading

Publications

Refereed Papers

  • Recent reference from PubMed and VetMedResource.
  • Carnevale E M (2004) Oocyte transfer and gamete intrafallopian transfer in the mare. Anim Reprod Sci 82-83, 617-624 PubMed.
  • Coutinho da Silva M A, Carnevale E M et al (2004) Oocyte transfer in mares with intrauterine or intraoviductal insemination using fresh, cooled, and frozen stallion semen. Theriogenology 61 (4), 705-713 PubMed.
  • Coutinho da Silva M, Carnevale E M et al (2002) Use of fresh, cooled and frozen semen during gamete intrafallopian transfer in mares. Theriogenology 58 (2/4) 763-766.
  • Carnevale E M, Maclellan L J et al (2001) Equine sperm–oocyte interaction: results after intraoviductal and intrauterine inseminations of recipients for oocyte transfer. Anim Reprod Sci 68 (3-4), 305-314 PubMed.
  • Carnevale E M (1996) Gamete intrafallopian transfer. Vet Clin North Am Equine Pract 12 (1) 47-60 PubMed.

Other sources of information

  • Loomis P R (2011) Semen Processing Techniques for Management of Subfertile Stallions. In: Proc of the Annual Meeting of the Italian Association of Equine Veterinarians. pp 18-22. Website: www.ivis.org (pdf download).
  • Coutinho da Silva M A (2011) Gamete Intrafallopian Transfer (GIFT) In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Blackwell Publishing Ltd, UK. pp 2945-2947.