Can gene splicing help with antibiotic reduction in animal production?

Panelists at the first day of the CFI's Strategy Conference on Animal Agriculture, which is focused on building trust with consumers, discussed what advances have been made at this point in breeding technology and what changes could be introduced when relying on new gene editing methods.

“Emerging genetic advancements have the potential to transform animal agriculture but at this time we have a lot of questions: What are the moral, legal and ethical arguments around some of these emerging genetic technologies and what about the regulatory considerations as well?” ​said moderator Barb Glenn, CEO National Association of State Departments of Agriculture.  ​

Some gene splicing advances could include disease-resistant animals, hornless dairy cattle and improved muscle development, said the panelists.

However, challenges remain in terms of how regulation would address animals developed through gene editing technology and what public perception would be, they noted.

How it works​

Animals produced trough a genome engineering or a gene editing process would be identical to animals bred to display the same trait, said panelist Alison Van Eenennaam, cooperative extension specialist in animal genomics and biotechnology at the University of California, Davis. However, instead of going through potentially lengthy selective breeding process, with gene editing a cut is made in an animal’s DNA.

That cut can cause a gene not to be expressed in the adult animal – like removing horns from dairy cattle, she said.

“It’s enabled by a group of things called nucleases and they’re specifically site directed nucleases, what that means is I can .... ​make a very specific cut in exactly the base pair [required] by knowing the sequence of the gene,”​ she said. After the cut, the chromosome tries to repair itself and can introduce a mutation that turns the gene off.

“Or you can be a little more prescriptive about it, and rather than let it do this thing called non-homologous end joining, you can make homologous repairs so you give it a donor template,” ​she said. “It will integrate [the template] and make targeted changes.”​

However, the process is separate from traditional genetic engineering because new DNA sequences are not being added to the existing gene, said Van Eenennaam. “You’re making a cut of DNA and when it repairs it, it inactivates that particular gene,”​ she added.

Antibiotic use reduction ​

Another potential application for the technology would be in disease prevention, said the panelists. The technology could be used to eliminate proteins that allow entrance to certain diseases.

The process has been used to develop pigs resistant to African swine fever and the porcine reproductive and respiratory syndrome virus, said Van Eenennaam. “[There is] no new DNA introduced, it is a genome edit that makes the animals resistant,”​ she added.  

“Genetic improvements to address things like disease are cumulative and permanent,” ​she said. “You don’t need give the animal a vaccination every year or to treat sick animals. I’d rather use genetics to approach that, if I can, than chemicals.”​

Regulation challenges​

But regulatory issues remain, said Van Eenennaam.

“Conventional breeding programs, whether they’re plants or animals, are not regulated by the federal government,”​ she said.

All animals that are created through a genetic engineering process are reviewed by the US Food and Drug Administration (FDA) because the transgene technology or introduced transgene used is considered a drug.

Additionally, the progeny and grand-progeny of the animal developed through that system also would be considered genetically modified, she said.

But regulations make an exception for animals that have been developed through traditional breeding and selection, said Van Eenennaam. That makes the regulation process unclear as you could get the same mutations through breeding as you can make in the gene editing process, she added.

“A really important question is – is this new gene editing technology, where we’re making changes in the DNA but not introducing transgenes, covered [by regulation]?” ​she said. “Does it have to go through this regulatory process? And quite frankly we don’t know. It’s that uncertain.”​