Genetic Engineering in Livestock

The first transgenic livestock were produced in 1985 by microinjection of foreign DNA into zygotic pronuclei. This was the method of choice for more than 20 years, but more efficient protocols are now available, based on somatic cell nuclear transfer (SCNT) which permits targeted genetic modifications. Although the efficiency of transgenic animal production by microinjection technology is low, many animals with agriculturally important transgenic traits were produced. Typical applications included improved carcass composition, lactational performance, and wool production as well as enhanced disease resistance and reduced environmental impact. Transgenic animal production for biomedical applications has found broad acceptance. In 2006 the European Medicines Agency (EMEA) approved the commercialization of the first recombinant protein drug produced by transgenic animals. Recombinant antithrombin III, produced in the mammary gland of transgenic goats, was launched as ATryn® for prophylactic treatment of patients with congenital antithrombin deficiency. Pigs expressing human immunomodulatory genes have contributed to significant progress in xenotransplantation research with survival periods of non-human primates receiving transgenic porcine hearts or kidneys approaching six months. Lentiviral vectors and small interfering ribonucleic acid (siRNA) technology are also emerging as important tools for transgenesis. As the genome sequencing projects for various farm animal species progress, it has become increasingly practical to target the removal or modification of individual genes. We anticipate that this approach to animal breeding will be instrumental in meeting global challenges in agricultural production in the future and will open new horizons in biomedicine.

‘Pharming’ can be defined as the use of transgenic animals or plants for the production of pharmaceutical proteins or peptides. Since the 1980s it has been proclaimed as an efficient and cost-effective method for the production of biopharmaceuticals. In 2006, the first therapeutic product produced in the milk of transgenic livestock gained approval, ATryn®, a recombinant form of human antithrombin III, produced by GTC Biotherapeutics. This was an important milestone but a long time coming, too long for some biotechnology companies. The near future will show if pharming can regain investor confidence, and whether society and the pharmaceutical industry will accept transgenic livestock as an alternative to more established production methods. There is cause for optimism for biopharmaceuticals represent a considerable and growing market opportunity and animal pharming has made considerable strides. In two decades a novel production platform has been established, new and groundbreaking technologies developed and the necessary regulatory framework put in place. This article highlights some of the obstacles pharming has faced and what the near future might bring.