Why are some animals more susceptible to diseases than others? Scientists at the Technical University of Munich (TUM) investigated this in more detail. They found genetic differences in livestock species that make individual animals less susceptible to certain diseases. In a large study, the researchers demonstrated the feasibility and efficiency of CRISPR-Cas9 editions.
The possibilities of genome editing in livestock breeding have not yet been systematically explored. The FORTiGe research association funded by the Bavarian Research Foundation now wanted to clarify how the molecular biological methods of genome analysis and genome editing can improve animal health. The researchers used genome-wide investigations and the CRISPR-Cas9 gene scissors for this purpose. With the help of the CRISPR-Cas9 method, DNA building blocks in the genome can be rewritten in a targeted manner.
The researchers exclusively targeted genetic changes that might also occur in nature. Such changes might also be achieved in the context of classical animal breeding, but this can take many generations and decades, whereas genome editing leads to the goal in a few generations.
In cattle, the scientists identified genes that significantly influence the birth process, the health of young animals and the resistance of the metabolism of cows. "Some of the identified genome sites can be used in the future to improve animal health," explains Ruedi Fries, Professor of Animal Breeding at TUM and Spokesman of the association.
The working group of Angelika Schnieke, Professor of Livestock Biotechnology at TUM, found a way to produce pigs that are resistant to edema disease by means of genome editing. This infectious disease mainly affects newly weaned piglets, i.e. weaned from the mother’s milk, the intestinal environment of which has become out of balance due to the diet change. In susceptible animals, pathogenic Escherichia coli germs can multiply greatly and lead to the death of piglets due to toxins - a reason why antibiotics are often used here so far.
In addition, genome-edited chickens have been bred which are resistant to the avian leukosis virus. The animals were produced by the group of Benjamin Schusser, Professor of Reproductive Biotechnology. Resistance was confirmed by extensive immunological investigations and infection experiments both in cell cultures and in live animals.
"The avian leukosis virus can lead to severe diseases and severe growth and laying depression in poultry," explains Prof. Schusser. "Research might now build up herds of animals that do not get sick because they are resistant to these viruses."
"In all studies, we used genetic changes as they might occur naturally," emphasizes Prof. Fries. For example, the gene variant leading to resistance to the edema disease, is found in certain pig breeds, but it is only rarely found in Bavarian breeding animals. The variant of a certain protein leading to resistance to the avian leukosis virus does not occur in chickens, but is found, for example, in quails.
"The research results open up realistic perspectives for supporting farmers in their efforts to improve animal health and welfare," summarizes Prof. Fries.