Transgenic animals are animals whose gene or DNA altered and manipulated with foreign desire gene. They are simply created by the microinjection of DNA into the fertilised egg of surrogate mother.
Advantage:

1. The main purpose of producing transgenic animals is to study the regulation of gene in body.
2. Transgenic animals contribute a great deal to study of disease. We can find out how gene fight against disease.
3. A major objective of transgenic animals is also to produce biological products, e.g. ,milk, blood, urine, silk.
4. Genetic engineering has the biggest hand in the line of making vaccine e.g., corona vaccine, BCG, DPT, Polio vaccine etc.
5. Transgenic animals are more sensitive to certain chemicals and drugs, so they used for chemical safety testing.

Rosie was a transgenic cow which contain 2.4 gram of protein per leter which is more than a normal cow. This milk contain human α - lectalbumine which is a very balance nutrient for the human body.