Embryo transfer programmes consist of a series of relatively simple techniques. However, each step in the process must be done correctly for the programme to succeed. The end result will only be as good as the weakest step in the process. Thus, attention to detail is essential.
Sometimes embryo transfer programmes are failures, usually because pregnancy rates are very low. Probably the main reason for failure is insufficient investment in training personnel. The second most common problem is insufficient animal resources. Unless large numbers of healthy, thriving cattle are available, embryo transfer will not work well, particularly when personnel are developing skills.
Facilities and equipment are also important, but are frequently over-emphasized. A clean laboratory work area is needed; mobile vans can be used for this purpose. Obviously, cows must be kept separate from bulls. An unusually common error is that recipients become pregnant from natural service rather than embryo transfer, which is not discovered until calves are born one oestrous cycle late or are of the wrong breed. It is clearly necessary to be able to catch animals for injections, insemination, embryo recovery and embryo transfer. Simple, well-designed pens, runways and head catches close to where animals can be fed are essential. Implicit in such a facility is the need for intensive management based on feed supplementation.
A generally successful approach is to build embryo transfer on a programme that has been successful for artificial insemination. Facilities and logistics of handling animals are similar for both techniques. Also, the skills of good oestrus detection and passing catheters through the cervix are an excellent foundation for embryo transfer. In fact, we do not recommend training people in techniques of embryo recovery and transfer until they are proficient in artificial insemination (meaning that they have inseminated well over 100 animals with good pregnancy rates).
TABLE 17
Examples of reasonable goals of embryo transfer programmes
To meet commercial objectives, i.e. to make a profit by providing services where commercial demand exists
To train personnel who are in demand to meet other goals
For research purposes, where embryo transfer is deemed the best approach to testing a hypothesis
For preserving genetic material of indigenous breeds in danger of extinction by cryopreservation of embryos
For importing embryos to provide new genetic resources and then increasing the numbers of animals of the new breed quickly
For national livestock improvement programmes such as MOET schemes in which embryo transfer fits into a well-thought-out overall programme
To test otherwise outstanding males and females suspected of being carriers of undesirable recessive genetic traits
A final thought is that many embryo transfer programmes suffer from not having clearly-thought-out goals. Frequently the goal is simply to establish a successful embryo transfer programme for reasons of prestige, or because it seems the wave of the future. Embryo transfer should be thought of as a technique such as oestrus synchronization or artificial insemination, rather than as an end in itself. Only rarely is it the method of choice for reproducing cattle. Even in so-called developed countries, use of embryo transfer has plateaued at about one per 500 calves born. Obviously this may change as new technologies such as sexing and cloning become inexpensive but except for a few special cases, we predict that embryo transfer will be used to produce fewer than 1 percent of the births of calves in any given country for the remainder of this century.
Examples of reasonable goals of embryo transfer are listed in Table 17.
Note that for some of these goals it is much less expensive to hire someone to do the work than to develop an embryo transfer programme de novo. In calculating the cost effectiveness of an embryo transfer application, administrators frequently fail to define the end product accurately, and thus misjudge actual costs. For instance, it is misleading to use cost per viable embryo or cost per pregnancy when a first-calf heifer entering the milking herd is the desired product. For a more thorough discussion of uses of embryo transfer, see Seidel and Seidel (1989).
