Background

The first successful embryo transfers were conducted in 1890 in rabbits at Cambridge, England.[1] Subsequently, there were only a few reports of embryo transfers in any species until the first calf was born in 1951. Commercial embryo transfer in farm animals started with cattle in North America in the early 1970s. The primary economic driving factor was the high prices being paid for various breeds of so-called exotic beef cattle imported in small numbers from Europe. Recently, it was estimated that approximately 1 out of every 300 dairy calves born in North America is from embryo transfer.[2]

Embryo transfer is usually used to increase the number of genetic offspring that a donor female can produce in a given unit of time, because recipients gestate the pregnancies to term. On the average, dairy cattle in North America produce only about three calves in their lifetime. Under some circumstances, with repeated superovulation, individual donor cows have produced more than 100 offspring in 2 to 3 years.

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