Assisted reproductive techniques in mares

A wide variety of assisted reproductive techniques (ARTs) are available to aid in managing aspects of equine reproduction. Embryo recovery and transfer can be used to obtain more than one foal per mare per year, and to obtain foals from mares that cannot carry a foal to term. Oocyte recovery and either transfer to the oviduct of an inseminated recipient mare (oocyte transfer), or intracytoplasmic sperm injection (ICSI) and embryo culture can be used to obtain foals from mares with some types of subfertility, such as problems of the tubular tract. ICSI can be used to obtain foals when sperm number or quality is low. Because of its ease of use for the mare owner and efficiency, oocyte recovery and ICSI is being used in some cases for management of normally fertile mares and stallions. Oocytes can be recovered from live mares by the referring veterinarian, and shipped overnight to a laboratory for ICSI, without any decrease in oocyte or embryo viability. In case of unexpected death of a mare, ovaries or oocytes can be transported to the ICSI laboratory for production of embryos. Embryos produced both in vitro and in vivo can be biopsied to determine their genetic makeup before they are transferred. Equine embryos can be vitrified successfully; collapse of the blastocoele cavity allows efficient vitrification of expanded blastocysts. In contrast, cryopreservation of unfertilized equine oocytes still has low success. Genetics of valuable animals can be preserved via nuclear transfer (cloning) and several commercial companies offer this service clinically.