Traditional cattle breeding has always involved modifying the genetics of animals, but the term “genetic modification” is often associated with more modern biotechnologies like genetic engineering and gene editing.
“Often when people hear the expression ‘genetic modification’ what comes to mind is the whole GMO debate and scary memes on the Internet, or that if you eat GMOs something bad will happen to you,” says Alison Van Eenennaam, UC Davis animal biotechnology and genomics extension specialist. “That narrative has been very hard to correct.”
Van Eenennaam was a featured speaker during Kansas State University’s Cattlemen’s Day on March 7. Genetic engineering, which has been around for about 30 years, involves introducing transgenic constructs from other organisms, such as Bt corn. However, this technology has seen limited use in animal production due to consumer pushback against GMOs and the difficulty of introducing new traits into animals, Van Eenennaam says.
A newer technology called genome editing or gene editing has emerged in the last decade.
“Gene editing is basically just conventional breeding, but done more intelligently,” she summarizes. “This allows for the targeted manipulation of an animal’s DNA without introducing foreign genetic material. For example, researchers have developed a ‘PRRS-resistant’ pig by knocking out a gene that the virus uses to infect the animal. Gene editing can also be used to introduce beneficial alleles from one breed into the elite germplasm of another, without diluting the desired genetics.”
In cattle, gene editing has been used to create knockouts for traits like disease resistance and heat tolerance, as well as knock-ins to introduce desirable alleles like the polled trait.
“In 2009, we were able to define the entire sequence of the cattle genome, which gave us a look at the genetic variation that exists between cattle breeds,” Van Eenennaam says. “In the case of cattle, that’s about 3 billion base pairs of DNA that make up the cattle genome.”
She explained there are two ways to gene edit cattle — cloning and microinjection into zygotes. “The key difference is that cloning starts with an edited cell line, while microinjection edits the zygote directly,” she says. “Ultimately, the goal is to produce a homozygous, non-mosaic animal where both alleles carry the desired edit, ensuring the trait is passed on to offspring.”
Van Eenennaam explains a few of the cattle-focused gene editing projects have centered around traits like polled, disease resistance, heat tolerance and muscle development.
In the swine industry, she says gene editing is being used to improve a pig’s resistance to Porcine Reproductive and Respiratory Syndrome (PRSV), a devastating disease that costs the swine industry about $1.2 billion per year in the U.S.
A gene editing project that could have a big impact the beef industry is surrogate sires or “artificial insemination on legs.” The process produces bulls that are generating semen from a different cell line. For example, a tropically adapted bull working in an environment where he is well suited, but his semen could be genetically, an Angus sire.
“You can basically do AI on legs, because you could naturally service with elite germplasm,” she says. “There’s a lot of different applications that have some potential to really benefit the beef industry.”
Gene editing technology still faces regulatory hurdles in the U.S., as well as the need to overcome perceptions among countries that buy U.S. beef.
Van Eenennaam says the main risks with gene editing are more reputational than safety-related, as activist groups may try to lump gene editing with GMOs. She encourages more discussion highlighting how gene editing can address issues like animal welfare and disease resistance in ways that align with consumer values.
Excited about the potential of gene editing to improve livestock production in a targeted and precise manner, she summarizes that regulatory approaches will be crucial in determining which applications reach the market and who can bring them forward.
You can watch her K-State Cattlemen’s Day presentation here: https://youtu.be/d7N7a6mYwDk
Your Next Read: Modern and Precise: Using Gene Editing to Change the Blueprint of an Organism
