Gene-edited livestock

In plain language

Gene editing tools such as CRISPR can change a specific letter, or a short stretch, of an animal's DNA. Breeders can use this to give an animal a trait that already occurs naturally in some animals, such as a short coat that helps cattle stay cool, or a hornless head so that calves do not need to be dehorned. Because the edit is passed on to offspring, a single edited animal can start a new breeding line.

Two examples have reached formal decisions in the United States. In 2022, the US Food and Drug Administration (FDA) said beef from two gene-edited heat-tolerant cattle, and their offspring, posed a low risk, so the developer could market them without a full FDA approval. In 2025, FDA approved a deletion in a gene called CD163 that makes pigs resistant to porcine reproductive and respiratory syndrome virus (PRRSV), a disease that causes large losses for pig farmers. Only pigs with two copies of the edit were resistant, and they resisted all the virus strains tested except one. Gene editing can also leave unplanned changes in the DNA, so developers must check for them and remove them before animals are sold.

Technical explanation

Gene-edited livestock are produced by introducing a targeted change, called an intentional genomic alteration (IGA), into embryos or cells. In the 2025 PRRS-resistant pig, the sponsor (Genus plc) used CRISPR-Cas9 cuts either side of exon 7 of the swine CD163 gene, so that repair removed the exon. The protein encoded by exon 7 is the part the virus uses to bind to the cell, so pigs with two copies of the deletion (homozygous) resisted all the PRRSV strains tested except KS06, while pigs with one copy (heterozygous) resisted none of the strains tested. FDA's review judged the risk that KS06 would matter as low because that strain does not circulate at an appreciable level in the US.

Off-target and unplanned edits are the main technical risk. For the PRRS pig, FDA's summary reports that the sponsor checked 182 predicted off-target sites, and found unintended edits at two of them in at least one founder pig. FDA says these edits are not expected to affect protein function, and selective breeding removed them from the population intended for commercial use. For polled (hornless) cattle, a 2019 bioRxiv preprint by Norris and colleagues, which analysed publicly available whole-genome sequencing data, reported an unintended heterozygous plasmid integration, along with a second copy of the repair template, at the target site. A UC Davis follow-up on six calves of a gene-edited bull reported that four also inherited a bacterial plasmid fragment, and the authors argue that plasmid integration must be screened for during editing.

Regulation differs by country. In the UK, the Genetic Technology (Precision Breeding) Act 2023 covers both plants and animals, and it defines a precision bred animal. The sources reviewed here did not confirm that the animal-specific rules are in force.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• The 2025 PRRS-resistant pig protects only pigs with two copies of the edit. Pigs with one copy were not resistant to any strain tested (FDA, 2025).
• The PRRS-resistant pig was not resistant to the KS06 strain. FDA judged that strain not to circulate at an appreciable level in the US, but this could change, and the sponsor must promptly report post-approval problems, such as breakthrough infections in homozygous pigs.
• The 2022 cattle decision was a low-risk determination under enforcement discretion, not a full FDA approval. The FDA primary page was not reviewed, so details of that decision rest on a news report.
• The 2019 preprint argues that screening must reliably detect plasmid and extra repair-template insertions, not only the intended edit.
• A 2022 UK survey of 848 respondents found that attitudes to gene-edited meat were bundled with attitudes to GM in general. The sample slightly over-represented rural, female and older respondents, and the study used chicken breast and a hypothetical bidding game, so its results may not generalise.
• The sources reviewed did not confirm the current status of animal-specific UK rules under the Precision Breeding Act 2023, and this profile does not state that status.

Possible future uses

Timeline

1. 28 Jul 2019bioRxiv preprint by Norris and colleagues reports unintended plasmid integration at the target site in polled cattle. Sources: [3]
2. 7 Oct 2019UC Davis reports that four of six calves from a gene-edited hornless bull also inherited a bacterial plasmid fragment. Sources: [4]
3. Mar 2022FDA issues a low-risk determination, under enforcement discretion, for beef from heat-tolerant PRLR-SLICK cattle. Sources: [2]
4. 23 Mar 2023The Genetic Technology (Precision Breeding) Act 2023 receives Royal Assent in the UK, covering plants and animals. Sources: [5]
5. 29 Apr 2025FDA approves the CD163 exon 7 deletion in pigs for PRRS resistance (sponsor Genus plc). Sources: [1]

Futures this could help bring about

How far away?

Meat from gene-edited animals in supermarkets

Pilots · 2 of 7 steps done

Glossary

Intentional genomic alteration (IGA)

A change to an animal's DNA made on purpose with genome editing, which FDA reviews as the regulated product.

Off-target edit

An unplanned change to DNA at a site other than the intended target.

Homozygous and heterozygous

An animal is homozygous for an edit when it has two copies of it, and heterozygous when it has one copy and one unedited copy.

Plasmid

A small loop of DNA, often from bacteria, used as a carrier in genetic engineering; unplanned plasmid DNA in an animal's genome is a sign of an editing error.

Sources

1. government report
   Freedom of Information Summary, NADA 141-609: Deletion of exon 7 of the CD163 gene in domestic pigs
   US Food and Drug Administration, Center for Veterinary Medicine, 29 Apr 2025. Accessed 21 Oct 2026.
2. news
   Beef from certain gene-edited cattle is safe to eat, FDA says
   Food Safety News, 9 Mar 2022. Accessed 21 Oct 2026.
3. preprint
   Template plasmid integration in germline genome-edited cattle
   Alexis L. Norris, Stella S. Lee, Kevin J. Greenlees et al.. bioRxiv, 28 Jul 2019. DOI: 10.1101/715482. Accessed 21 Oct 2026.
4. university press release
   Genome-Edited Bull Passes on Hornless Trait to Calves
   Amy Quinton. UC Davis News, 7 Oct 2019. Accessed 21 Oct 2026.
5. government report
   Genetic Technology (Precision Breeding) Act 2023
   legislation.gov.uk, 23 Mar 2023. Accessed 21 Oct 2026.
6. peer reviewed paper
   Gene-Edited Meat: Disentangling Consumers' Attitudes and Potential Purchase Behavior
   Frontiers in Nutrition, 5 Apr 2022. DOI: 10.3389/fnut.2022.856491. Accessed 21 Oct 2026.
7. news
   Genus PIC awaits FDA OK as global approval push for PRRS-resistant pigs intensifies
   AgNavigator, 18 Apr 2025. Accessed 21 Oct 2026.

Revision history

3 changes since this profile was created.