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Embryo Transfer in Cattle
Glenn Selk Extension Animal Reproduction Specialist

History of Embryo Transfer Embryo transfer  in cattle has recently gained considerable popularity with seedstock dairy and beef producers.  Most of the applicable embryo transfer technology was developed in the 1970s and 1980s; however, the history of the concept goes back much farther.  Embryo transfer was first performed and recorded by Walter Heape in 1890.  He transferred two Angora rabbit embryos into a gestating Belgian doe.  She went on to produce a mixed litter of Belgian and Angora bunnies.  Embryo transfer in food animals began in the 1930s with sheep and goats, but it was not until the 1950s that successful embryo transfers were reported in cattle and pigs by Jim Rowson at Cambridge, England.  The first commercial embryo transfers in this country were done in the early 1970s.  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 1970s, that embryo transfer grew in popularity.

Why Consider Embryo Transfer in Cattle?

The reproductive potential of each normal newborn calf is enormous.  There are an estimated 150,000 potential “eggs” or ova in the female and countless billions of sperm produced by each male.  By natural breeding, only a fraction of the reproductive potential of an outstanding individual could be realized.  The average herd bull will sire 15 to 50 calves per year and the average cow will have one calf per year.  With artificial insemination, it is possible to exploit the vast numbers of sperm produced by a genetically superior bull, however the reproductive potential of the female has been largely unutilized.  She will produce an average of eight to 10 calves in her entire lifetime under normal management programs.  Like artificial insemination has done for the bull, embryo transfer is a technique that can greatly increase the number of offspring that a genetically important cow can produce.

How is Embryo Transfer Performed on Cattle? Virtually all commercial embryo transfer done today uses nonsurgical recovery of the embryos rather than surgical techniques.  The process involves several steps and considerable time as well as variable expense.

1)  Selection of the donor cow The first step is the selection of the donor cow.  Beef producers will differ in their opinions regarding the criteria for selecting a genetically outstanding cow.  Whether the criteria be performance records, show ring appeal, or both, consideration must be given to potential dollar value of her calves.  As we will see later, considerable expense can be incurred in achieving a successfully transferred pregnancy.  Therefore, the sale value of the newborn calf should be high enough to warrant the added expense of this procedure.  Because dairy cattle are selected more routinely on one major trait (milk production), the decisions concerning donor cows are actually somewhat less complicated than in beef cattle.  However the economic considerations are equally important.  Embryo transfer is not a “cure-all.”  It does not make average cattle good or good cattle better.  It is suitable for a limited number of seedstock producers with beef or dairy cattle that can be breed or species “improvers” for one or more economically important traits. The potential donor cow should be reproductively sound to produce maximal results.  This means that she should have a normal reproductive tract on rectal palpation and have a normal postpartum history, especially with regard to cycle lengths of 18 to 24 days.  Both beef and dairy cows should be at least 60 days postpartum before the transfer procedure begins.  It has been suggested that prospective donor cows in embryo transfer programs be selected on the following criteria:

 • Regular heat cycles commencing at a young age.

• A history of no more than two breedings per conception.

• Previous calves having been born at approximately 365day intervals.

• No parturition difficulties or reproductive irregularities.

• No conformational 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 obese cow and the thin cow will have reduced fertility, so it is important that the donor cow be in an appropriate body condition score at the time of embryo transfer.

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(See OSU Extension Circular E-869 to learn appropriate body condition for beef cattle and OSU Extension Leaflet L-221 for dairy cattle.) Oklahoma Cooperative Extension Fact Sheets are also available on our website at: http://osufacts.okstate.edu