Embryo Transfer in Cattle
Embryo transfer was first performed by Walter Heap in 1890. He transferred two Angora rabbit embryos into a gestating Belgian doe. She went on to have a mix litter of Angora and Belgian bunnies. Embryo transfer in market animals began in the 1930’s using sheep and goats, but it was not until the 1950’s that successful embryo transfers were reported in cattle and pigs by Jim Rowson in Cambridge, England. The first commercial embryo transfers in this country were done in the early 1970’s. Initially, embryos were recovered from valuable donors and transferred to recipient animals using surgical procedures. It was not until non-surgical methods were developed in the late 1970’s that embryo transfer became popular.
The first step of embryo transfer is selecting a donor cow. Everyone has there one opinions as to what the standards are fore a genetically outstanding cow. Whether the standards are performance records, show ring appeal, or both, you must also think about the potential dollar value of her calves. It has been suggested that prospective donor cows in embryo transfer programs be selected on the following standards:
1. Regular heat cycles starting at a young age.
2. A history of no more than two breedings per conception.
3. Previous calves were born at no more no less than 365 day intervals.
4. No parturition difficulties or reproductive irregularities.
5. No conformation or detectable genetic defects.
She should be maintained at the level of nutrition appropriate for her size and level of milk production. Both the very fat cow and the thin cow will have reduced fertility, so it is important that he donor cow be in good body condition at the time of the transfer.
The next step in the embryo transfer process is superovulation. Superovulation is releasing more than one egg in a single estrus. Cows and heifers that are properly treated can release 10 or more egg cells during one estrus. Some cows are superovulated...