Techniques to improve the quality of farm animals

a) Embryo manipulation

In this method, the fertilized egg is bisected at the two celled stage and each half is transplanted into different regions of the uterus. Using this method the reproductive rate is doubled as we know that female sheep and cattle produce, on an average, one offspring per pregnancy. Hence the farmers can easily increase their farmstock.

This technique can also be used to conserve rare breeds. After fertilizing their eggs in the laboratory , the young embryos or rare animals are dissected into anything from 2-8 cells. Each cell, is then transplanted into a surrogate mother of a common breed where it grows to produce a new individual of the rare type.

Another variation of this technique allows surrogate mothers to carry embryos of a different species e.g. Horses giving birth to zebras from zebra embryos implanted at the blastocyst stage. The outer layer of zebra embryo is exchanged with the trophectoderm of the horse embryo in order to make it acceptable to the surrogate mother. This exchange of the layer does not affect the development of the inner cell mass which is the true embryo-forming region.

b) Embryo cloning

Using this technique it is possible to produce many genetically identical copies of an animal. This method has been used to clone mouse however, research is going on to standardize this method to obtain clones of cattle with desirable traits e.g. cows with high milk production etc.

Following steps are used in this method:

a) an egg from the donor is grown to blastocyst stage under laboratory conditions.

b) The egg is dissected to remove the inner cell mass.

c) The mass cells are separated into individual cells.

d) Injection of a nucleus from each of these cells into a one-celled embryo containing two pronuclei.

e) Removal of pronuclei followed by culturing of embryos in the laboratory until the blastocyst stage.

f) Transplantation of these embryos into surrogate mothers.