Genome editing can be used in breeding schemes to speed up the increase in frequency of a desired trait such as the absence of horns in cattle.
Researchers at Wageningen University and Research Animal Breeding and Genomics show that genome editing can be used in breeding schemes to speed up the increase in frequency of a desired trait such as the absence of horns in cattle. The time until all animals have the desired genotype can potentially be reduced four-fold, when compared to classical selection. Results are published in Genetics Selection and Evolution and is featured on their website.
We investigated the impact of applying the novel technology of genome editing in a livestock breeding scheme using computer simulation. Genome editing is a precision tool that allows changing the DNA code at a specific location. The trait polled, which indicates the absence of horns, is controlled by a single gene in cattle. The location of the gene and the alleles that are present in cattle are known.
Some cattle breeds are completely hornless whereas for other breeds, such as the Holstein Friesian breed, only a small percentage of animals are without horns. This percentage can be increased by means of selection but this will come at the price of reduced progress in other desired traits. By applying genome editing breeders would be able to select animals with the highest genetic merit for the target traits, irrespective of the hornless trait. Subsequently genome editing can be used for some selected animals to make sure that the hornless trait is also transmitted.
We compared selection based on a DNA test with a combined strategy of selection based on a DNA test and genome editing. Results showed that the hornless trait can be introduced in the population much faster when genome editing and genomic selection were combined. The reduction in selection response for other desired traits is small when we assume that genome editing is 100% efficient. Currently, the efficiency of gene editing is much lower than 100%. With the current levels of efficiency for genome editing, the introduction of a monogenic trait using genome editing would still come with a considerable reduction in the selection response for the other traits.
This Breed4Food study illustrates some of the possibilities and limitations of genome editing in selective breeding schemes for livestock. Knowledge about these is needed in the societal debate on the use of genome editing techniques.