Genetically modified farm animals and fish in agriculture: A review

Developments in biotechnology over the past 25 years have allowed scientists to engineer genetically modified (GM) animals for use in various areas of agriculture and medicine. The great majority of GM animals and fish are currently only at the research stage. However, some animals with an anticipated use in food production are close to reaching the grocery shelf at least, they will be soon available for marketing. GM livestock include many different kinds of animals and species modified with the intention of improving economically important traits such as growth-rate, quality of meat, milk composition, disease resistance and survival. Pigs have been engineered to grow faster and to produce more meat with less feed; the composition of pork has also been improved for healthier human consumption. Scientists have paid particular attention to pig health, raising piglet survival rates, reducing the risks of infectious disease, and fortifying the porcine immune system. Sheep have been modified to improve wool production and immunity, and to reduce the risk of mortality following infections by bacteria and lethal viruses. Growth-rate in chickens has been increased with only limited success, because conventional selection has already improved this trait close to its biological limit. However, disease resistance (e.g. to H5N1) and the survival of newly hatched chicks have been improved. Udder health and survival are the most important traits improved by transgenic technology in cattle. GM cows with resistance to BSE have been bred. Similar traits are targeted in fish, dominated by salmon, carp and tilapia species, where the focus is on meat production, meat quality, and disease resistance. The number of GM farm animals and fish developed in laboratories is increasing, but for the present the number of species close to entering the market remains small. (C) 2013 Elsevier B.V. All rights reserved.