The decrease of areas suitable for farming hinder the production of enough food to feed the 8.5 billion people estimated to live in the world in 2030 while also maintaining proper welfare of food-producing animals. While current management and breeding practices have helped to improve animal productivity to enhance milk, meat, pork and poultry production, they are not sufficient to appease hunger in the near future and new approaches must be considered. Genetic engineering technologies have the potential to reduce disease, increase nutritional content of food and resolve animal welfare concerns thereby contributing to the sustainability of animal agriculture and conservation of natural resources.
Animals have long been bred to propagate desirable traits, be it high levels of growth or milk production or for disease resistance. Naturally occurring differences in DNA sequence throughout the genome are responsible for differential expression of traits between individuals. It takes many generations to introduce desired traits into a population and often the desired trait is accompanied by detrimental traits, for example impaired reproduction, as it is impossible to control what pieces of DNA the offspring inherits by breeding alone.
Current genetic technologies enable the precise modification of DNA to mimic the naturally occurring differences in DNA sequence. The most recently developed technology is termed gene editing and allows for the deletion, replacement or addition of DNA at a specific location. With this technique, the DNA of the animal is cut at a desired spot by the use of custom molecular scissors that consist of small pieces of RNA or DNA and a protein. Once cut, the DNA repairs itself often resulting in deletions or if exogenous DNA with a desired sequence change is also introduced, that piece of DNA will insert itself into the cut location. In this fashion it is possible to specifically change anywhere from several thousand down to one single base in the background of the 3 billion bases that make up the genome of an animal.
Gene editing is the least drastic, most specific and current state-of-the-art technique used in genetic engineering, being extremely precise at mimicking naturally occurring variations in DNA sequence in a seamless manner. This approach is less expensive and faster to recapitulate naturally occurring DNA sequences in the genome of animals that are already known for their production value than is breeding and selection. For instance, gene editing has been used to produce dairy cows without horns and double muscle beef cattle, solutions to current problems in animal handling and food production, respectively.
Another approach used in genetic engineering is the insertion of a gene encoding a protein with a specific functionality into the genome of an animal that lacks that particular function in order to impart the desired attribute in the species of interest. For this to be possible, the DNA of the gene of interest is isolated from the genome of origin, coupled to DNA control elements to limit the expression of the novel protein to a specific tissue or a period of time in the animal’s life and then introduced so that the new DNA inserts itself into the genome of the animal of interest, usually at a random location.
Inserting new genes in livestock genomes makes possible the generation of herds that are resistant to diseases or capable of preventing the dissemination of disease to healthy animals, which has huge impact on both production and animal welfare, and could especially improve the lives of people in areas that are already affected by hunger in Africa and Asia where the health and productivity of farm animals is poor and does not allow for adequate production of food. The insertion of genes can also allow the use of animal products to improve human health. Combined with advanced gene editing technologies, genetic engineering allows modification to livestock genomes to be very precise, bearing infinite possibilities to solving problems with food production, animal welfare and human health in a very safe, reliable and replicable manner. Following are examples of practical applications of animals developed through genetic technologies which address the needs of a growing population with respect to environmental impact of farming, disease resistance in animals and human health.