Embryo Transfer

 embryo is collected from a donor female and then transferred into a recipient female where the embryo completes its development.  Donor Female – must have outstanding genetics, be healthy, and reproductively sound

History  1890 – first embryo transfer done in rabbits  1951 – first transfer in cattle  profitable for producers of registered purebred animals  done in cows, horses, goats, sheep, deer, elk, bison, wildcats, and camels for racing

Superovulation:  refers to the release of many oocytes (eggs) during a single estrus period  treat with gonadotropins (hormones capable of promoting gonad growth and function  treat with FSH to induce the maturation and ovulation of a larger than normal number of oocytes

 Superovulation one time – 0-20 embryos with 7 normal  Superovulation three times – 9-12 calves normal  Non-superovulated cow – harvest a single ovum at every estrus = 5 calves in one year  ** A mare does not respond to superovulation treatment**

Steps in Embryo Transfer:  Superovulation of donor with gonadotrophins  AI (5 days after initiating superovulation) – inseminate several times  Nonsurgical recovery of embryos (6-8 days after AI)  Foley catheter for recovery of embryos  Isolation and classification of embryos  Storage of embryos indefinitely in liquid nitrogen or at 37 degrees C or room temperature for 1 day  Transfer of embryos to recipients surgically or nonsurgically  Pregnancy diagnosis by palpation through the rectal wall 1- 3 months after embryo transfer  Birth (9 months after embryo transfer)

Non-surgical Recovery  clean genital area  give local anesthetic in rump and hip  insert Foley catheter into vagina and through cervix  fluid forced from the catheter into the uterus to flush out embryos  fluid collected in a special container  embryos filtered

Non-surgical Transfer:  Embryos that pass inspection are loaded into an AI straw  Insemination rod is passed through the recipients cervix and into her uterus  Embryo is expelled into the uterine horn that is on the same side as the ovulated ovary

Surgical Recovery:  Unfertilized eggs must be collected near ovulation (used in vitro fertilization)  Collected any time between fertilization and implantation (usually after they migrate to the uterus)  Usually done 6-9 days after estrus  Method of choice in sheep, goats, and hogs

Surgical Transfer  embryos in the early stages of development must be deposited in the oviducts  Conception rates 5% better  done by a midline laparotomy (incision in abdominal wall) with general anesthesia OR through a flank incision with local anesthesia

Success Depends On:  age and quality of embryos  site of transfer  degree of estrus synchronization between the donor and recipients  number of embryos transferred  in vitro culture conditions  skill of personnel  management techniques