In order to breed livestock with more desirable traits for food production, such as disease resistance, better meat, and dairy quality, or heat tolerance, many farmers employ selective breeding or more modern techniques such as artificial insemination. Both approaches, however, have their limitations that could be superseded by gene editing with CRISPR technology, scientists argue in a new study.
Although food availability has increased along with the growing human population over the last 30 years, there are still 800 million people suffering from malnutrition, most of whom live in developing nations. In areas where food security is lacking, ruminant livestock (i.e. sheep and goats) often plays a crucial role in the food chain. But while the population of livestock has relatively kept up with our growing nutritional needs, there is still much room for improvement.
For the last six years, an international scientific collaboration involving researchers at Washington State University, Utah State University, University of Maryland, and the Roslin Institute at the University of Edinburgh in the U.K., has been working on speeding up and improving livestock food production using gene-editing techniques.
In a new study, the researchers have presented their findings. They claim they have created pigs, goats, and cattle that can serve as "surrogate sires" -- initially sterile males that produce sperm carrying only the genetic traits of an "elite" donor animal. In this context, "elite" refers to animals that have genetic traits that make them more resistant to disease and produce offspring with desirable characteristics in terms of food production.
"With this technology, we can get better dissemination of desirable traits and improve the efficiency of food production. This can have a major impact on addressing food insecurity around the world," said Jon Oatley, a reproductive biologist with Washington State University's College of Veterinary Medicine. "If we can tackle this genetically, then that means less water, less feed and fewer antibiotics we have to put into the animals."
Oatley and colleagues used CRISPR-Cas9 to breed mice, pigs, goats, and cattle that lacked a gene called NANOS2. The gene encodes the expression of molecules that are specifically related to male fertility (i.e. sperm production).
Males lacking the gene grew up sterile but otherwise healthy. They then received a transplant of sperm-producing cells in their testes from other animals. The animals then produced sperm that had the genetic material from the donor.
Surrogate mice fathered healthy offspring who turned out to carry the genes of the donor mice. The researchers also bred sterile male pigs, goats, and cattle, but these larger animals haven't mated yet.
"This shows the world that this technology is real. It can be used," said Whitelaw. "We now have to go in and work out how best to use it productively to help feed our growing population."
Farmers often use artificial insemination to breed livestock such as cattle that have the most desirable genetic characteristics. However, this is an expensive breeding technique that requires either animal proximity or strict control of their movements. For goats, artificial insemination is even more challenging, often requiring surgical procedures.
"Goats are the number one source of protein in a lot of developing countries," Irina Polejaeva, a professor at Utah State University, said in a statement. "This technology could allow faster dissemination of specific traits in goats, whether it's disease resistance, greater heat tolerance or better meat quality."
This is where surrogate sire technology could come in handy, enabling ranchers and herders to have their animals roam freely. Females with a deactivated NANOS2 gene remain fertile, so they can be subsequently used to birth sterile males to be used as surrogate sires.
That being said, this approach is currently impossible at a commercial scale due to regulations, as well as public perception. According to Oatley, gene editing involves making specific, small changes that could occur naturally, and does not combine DNA from different species.
"Even if all science is finished, the speed at which this can be put into action in livestock production anywhere in the world is going to be influenced by societal acceptance and federal policy," said Oatley. "By working with policymakers and the public, we can help to provide information assuring the public that this science does not carry the risks that other methods do."
The findings appeared in the Proceedings of the National Academy of Sciences.
