Gone are the days where a natural conception was the only way to become pregnant thanks to the advent of treatments such as in vitro fertilisation (IVF) and embryo transfer. IVF is where the egg is fertilised outside the body, i.e. in vitro by sperm, whereas embryo transfer describes the process by which embryos are transferred back into the uterus in order to result in pregnancy. These methods may be used for a number of reasons, particularly if the individuals in question are unable to have children naturally.

Within the veterinary species, embryo transfer is also a useful method to help achieve pregnancy. In farm animals, embryo transfer involves taking embryos from one animal and transferring them to another animal until the pregnancy is complete. There are a number of reasons why this method would be preferable as a way to establish pregnancy compared to natural conception. These can include the lack of fertility by some animals, or to prevent the passing on of any known genetic traits that would be undesirable in offspring. However, one of the main reasons embryo transfer is used is to increase pregnancies in certain females that possess certain characteristics (Merck Veterinary Manual). In this way, the practitioner can choose specific traits that would be required in the eventual offspring as opposed to breeding two animals and ‘hoping for the best’.

In addition, this method can be important from an experimental and immunological point of view. As has been previously discussed on the website, during pregnancy the maternal immune system must tolerate the partly foreign foetus which expresses genes from both the mother and the father. Although the mother’s genes are not regarded as foreign by the maternal immune system, the father’s genes are, resulting in a plethora of research dedicated to understanding how the father’s genes are tolerated during pregnancy. Embryo transfer can therefore be a good way to achieve a controlled pregnancy that can be studied to try and understand interactions between the immune system and the foetus. For more information on this topic, please read previous articles published on the website.

Embryo transfer has been shown to have high success rates in horses and cattle, ranging from 50% to over 90% and 56.1% to 77.1% respectively (Allen WR, 2005 and Hasler JF, 2001). These figures help to demonstrate how effective this method can be in establishing pregnancy, especially in cases where the animal is unable to conceive naturally. It is therefore easy to see the arguments for carrying out embryo transfer within the veterinary species, made easier in part due to the ever advancing and readily available veterinary ultrasound technology.

Nevertheless, the drawbacks of methods such as embryo transfer must also be taken into consideration. When compared to either a natural conception or standard breeding programmes, embryo transfer is much more expensive. Additionally, this method must be carried out by a skilled practitioner, further increasing the costs involved. The sustainability of embryo transfer should also be deliberated – in its essence, this method is striving to create a ‘perfect offspring’ that contains traits most desirable for its eventual outcome. These could be physical traits (for example, if a horse is bred for racing certain characteristics would be required), increased beef quality (in cattle reared for meat), or wider birthing canals (helping the animal give birth unaided). However, the long term implications of such approaches should be given some thought.

Consequently, embryo transfer is a useful application that is used in the veterinary species for several reasons. As with any technique however, the advantages should be assessed alongside the disadvantages to make sure the correct decision is made for each individual situation.