Oocyte Transfer Services

Although embryo transfer provides a means of obtaining pregnancies from some mares that might not otherwise be capable of producing offspring, some mares cannot provide embryos for transfer. Mares in which embryo transfer may not be successful include those with: 1) ovulatory failure, 2) chronic and severe uterine infection, or 3) anatomical problems (e.g. cervical adhesions, etc.). However, these mares could be used as oocyte (egg) donors and continue to produce foals through newer reproductive technologies such as oocyte transfer and intracytoplasmic sperm injection (ICSI). In addition, offspring can be produced from stallions with low sperm numbers and/or poor sperm quality.

The successful application of these technologies requires that oocytes be collected directly from the ovaries of the donor mare. Oocytes are often collected by transvaginal, ultrasound-guided follicular aspiration. After oocytes are collected, they are generally incubated in a culture medium so that they mature to the stage where they are capable of undergoing fertilization.

The oocyte transfer procedure involves placement of a donor mare's oocyte (eggs) into a recipient mare's oviduct (fallopian tube). The recipient mare is artificially inseminated with the desired semen prior to oocyte transfer; therefore, fertilization and embryo development occur within the reproductive tract of the recipient mare. The recipient mare's egg is removed, so it does not become fertilized.

The ICSI procedure involves micro-injection of a single sperm cell into the cytoplasm of a mature oocyte, which physically causes fertilization. Because ICSI utilizes a single sperm cell for each oocyte, this procedure holds tremendous potential for the production of foals using semen from stallions with low numbers of sperm or poor sperm quality.

Under experimental conditions when performing these procedures on young fertile mares, the success rate of the ooctye transfer procedure is approximately 70 to 80% per transfer. However, when these procedures are performed on aged, chronically subfertile mares, the success rate of the oocyte transfer procedure is about 40% per transfer.

These procedures provide alternatives for reproductive management of mares and stallions that have not been able to produce offspring using more conventional procedures. For further information, please contact Dr. Elaine Carnevale (970) 491-8626.