Embryo Transfer in Cattle,Embryo Transfer,Inferior Genes,Superior Genotype,Luteinising Hormone (LH)

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	Embryo Transfer in Cattle Young embryos of cattle of superior genotype are collected prior to their implantation in uterus, and are implanted in the uterus of other females of inferior genotype where they complete development; this is called embryo transfer. The chief objective of embryo transfer is to obtain several progeny per year from a single female of superior genotype. (II) a country like India, most cattle are of inferior genotype with rather low productivity, while superior genotype females are limited in number and of high price.
Therefore, a programme of artificial insemination (AI) was widely used in an effort to improve our cattle breeds. A limitation of AI is that superior genes (50%) are contributed by only the male side, while the female contributes (50%) inferior genes. In contrast, in embryo transfer technique, the inferior females used as surrogate or substitute mothers do not contribute any genes to the progeny; they only serve as extremely sophisticated natural incubators for the normal development of young embryos. As a result, the progeny obtained by embryo transfer are of superior genotype.
The technology of embryo transfer in cattle may be briefly summarised as follows. 1. A genetically superior and high productivity female serves as the donor of embryos to be transferred. 2. Healthy, young females of inferior genotype are selected to be the recipients of embryos to be transferred; these females are called surrogate or substitute mothers. 3. The donor females are treated with appropriate doses of the selected gonadotrophin, e.g., follicle stimulating hormone (FSH) or luteinising hormone (LH), to increase the number ova released at the time of ovulation; this is called superovulation. Under optimum treatment conditions, a single female can provide up to 15 embryos in a single cycle. The chief objective of superovulation is to greatly increase the number of embryos recovered per female in a single cycle.
4. When the donor female is in heat, it is artificially inseminated using semen from a genetically superior bull of top pedigree. 5. The fertilized eggs/young embryos are collected by flushing the uterus of donor females with a special nutrient solution 7 days after the insemination. The embryos are examined under a stereoscopic microscope and normal looking healthy embryos are selected. 6. The selected embryos are incubated in a special nutrient medium at 37°C till their transfer into the surrogate mothers. Alternatively, they may be frozen and stored in liquid nitrogen for future use. 7. A single embryo is transferred into the uterus of each surrogate mother. It is important that the oestrus cycles of donor and surrogate mothers are synchronized by administering prostaglandins to provide the optimum uterine environment for survival, establishment and normal development of the young embryos.