Embryo sexing requires that a small biopsy be removed from the embryo and analyzed using DNA technology to determine the sex. This technology is considered cost effective and is utilized quite commonly in dairy cattle. On average, the pregnancy rate with frozen-sexed embryos is slightly lower that non- manipulated embryos. The procedure is quite tedious, time consuming and adds cost to frozen embryos. It's use questionable as to it being cost effective in beef herds. The biopsy also penetrates the zona pellucida (shell) which yields the embryos non exportable to some countries.
Ultrasonography is used commonly to evaluate ovaries, detect early pregnancy (27 days), and determine the sex of the fetus (55-70 days gestation). Ultrasound is a very useful tool and can help utilize recipients more efficiently by early pregnancy testing and re-use of open recipients. Examining the ovaries of Donor cows and recipients can also be useful in determining if the ovaries are functioning properly. Ultrasound is an excellent tool to use in general reproductive examinations as well.
Embryo Splitting has been used more commonly in the past. It is used to produce identical twins. The number of calves from a given number of embryos can be increased, however twice as many recipients are needed and the pregnancy rate id decreased. The high cost of recipients makes this technology questionable from an economics standpoint.
IVF or In-Vitro Fertilization is basically "test-tube calves". This procedure is quite effective in producing embryos, however the pregnancy rates can be disappointing and the abortion rates are high with high incidence of giant calves which leads to low numbers of healthy live calves. This technique is practical for very valuable cows that will not reproduce using conventional ET. Frozen IVF embryos yield varying and mostly disappointing pregnancy results.
Cloning uses ET as part of the process to produce pregnancies. This technology has greatly improved and is restricted to research and very valuable animals such as transgenic animals like Dolly the sheep that are used to produce rare pharmaceuticals. In Canada there are presently restrictions on selling production (semen) from cloned or genetically modified animals.
Embryo transfer has come a long way in the past 30 years with the technological advances. The thing that hasn't changed is the fact that you should still only flush the genetically superior donors with a track record. Economics still rules the decisions. Now more than ever ET is used for movement of genetics worldwide. More now than ever, the good ones are bringing a premium and are easy to market. Embryo transfer is a tool to help get more of those "good ones".