Transgenic Animals | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Transgenic Animals

• The goal of animal biotechnology is to create animals with modified DNA by incorporating genes from sources outside their germplasm using recombinant DNA technology.
• Transgenic animals exhibit economically important traits such as enhanced disease resistance, growth, lactation, reproduction, and the production of pharmaceuticals.
• For producing high-value pharmaceuticals, genes encoding animal proteins like tissue plasminogen activator (tPA) can be connected to regulatory sequences for high gene expression in the mammary gland.

Production Process of Transgenic Animals:

• Identification, isolation, and preparation of the desired gene for insertion into a fertilized egg.
• Obtaining and preparing host cells (fertilized eggs or early embryos) for gene insertion.
• Transfer of the desired gene into the host cell.
• Duplication of the resulting recombinant embryo and transplantation of multiple embryos into synchronized recipient cows.

Challenges and Limitations:

• Existing transgenic animals face limited utility due to high production costs, low efficiency of microinjection techniques, and the lack of suitable viral vectors for most livestock species.
• The random insertion of transferred DNA into the host genome leads to a lack of control over the gene transfer process.

Methods of Gene Transfer:

• Gene transfer into preimplantation embryos can be achieved through viral vectors, microinjection, and stem cells derived from embryos, allowing DNA insertion at specific sites within the genome.

Applications in Livestock:

• Current research primarily focuses on manipulating the growth performance of farm animals, with an emphasis on expressing genes like bovine somatotropin (bST) in pigs for improved growth rates and feed efficiency.
• Efforts have been made to control side effects like hyperglycemia and stress susceptibility through the use of alternative enhancers.

Lactation and Dairy Production

• Transgenic animals can be utilized to produce human proteins in sheep's milk for medicinal purposes and reduce mastitis incidence in dairy cows.

Transgenic Sheep for Protein Production:

• Transgenic sheep were utilized to generate essential human proteins like a-1-antitrypsin and blood clotting factor IX.
• Introduction of a gene into sheep for B-lactoglobulin (BLG) resulted in significant changes in milk constituents.
• Expression levels surpassed the natural concentration of BLG in sheep milk.
• These experiments show promise in creating animals with enhanced nutritional and economic value.

Transgenic Technology in Milk Production:

• Researchers at Tufts University and Genzyme Corporation successfully developed transgenic goats producing enzymatically active tissue plasminogen activator (tPA) in their milk.
• tPA aids in dissolving blood clots, potentially reducing production costs significantly.
• Transgenesis has been used to reduce mastitis in dairy herds by introducing lyphostatin-producing genes into livestock.
• Manipulating milk composition through transgenesis holds promise for improving animal health.

Challenges and Adverse Effects of Transgenic Livestock:

• Livestock expressing growth hormone fusion genes have experienced joint diseases, lethargy, infertility, dermatitis, and renal issues.
• Difficulties in breeding these transgenic animals pose significant challenges to the efficient and economical alteration of livestock performance.