Argentine lab unveils first CRISPR‑edited foals aimed at polo, drawing breeder backlash

Five foals born at an Argentine clinic are the first horses scientists say have been genetically edited using CRISPR‑Cas9, a development that Kheiron Biotech says could change horse breeding while prompting bans and protests from parts of the polo community.

Kheiron Biotech, based near Buenos Aires, said the foals were cloned from an award‑winning mare and altered with CRISPR to modify myostatin, a gene known to limit muscle growth. The company said the edit was intended to increase muscle fibers associated with power and speed for use in polo. The animals are about 10 months old and remain in a birthing and rearing facility in San Antonio de Areco.

The announcement has drawn immediate opposition. The Argentine Polo Association has moved to ban gene‑edited horses from competition, and about 50 breeders have signed a letter asking the national breeders' association not to register animals produced with gene editing. Benjamin Araya, president of the Argentine Polo Association, said the technique "takes away the charm" and the "magic of breeding," while breeder and former professional player Marcos Heguy said gene editing "ruins breeders." Association officials acknowledged practical problems in enforcing a ban because current registration systems do not clearly distinguish cloned, genetically edited and conventionally bred horses.

Kheiron co‑founder and scientific director Gabriel Vichera, who began work on cloning after seeing high auction prices for elite mares, has previously said the firm developed its first cloned horse in 2013 and later used CRISPR in research on equine embryos. The company also has produced gene‑edited livestock embryos in past years, according to materials provided by the firm.

CRISPR‑Cas9 is a gene‑editing tool that makes precise cuts in DNA and can be used to remove, add or alter small sections of the genome. Researchers say editing myostatin can increase muscle mass by reducing a natural brake on muscle growth; similar approaches have been studied in other species. Supporters argue that targeted edits can accelerate traits that would otherwise take multiple breeding generations to achieve.

Some scientists welcomed the demonstration that CRISPR can be applied in horses. Molly McCue, a veterinary clinician scientist at the University of Minnesota, said it is technically notable to show CRISPR works in equine animals and that breeding mixes art with science. Ted Kalbfleisch, a geneticist at the University of Kentucky, said inserting a known natural DNA sequence to replicate a trait seen in healthy animals is less speculative than attempts to create novel edits, but cautioned about attempts that rely on guesswork.

Opponents have raised ethical and competitive concerns. Polo is an expensive sport in which players routinely use multiple mounts per game; Argentina exported roughly 2,400 polo horses last year and its bloodlines dominate many top international tournaments. Unlike horse racing, polo historically allows cloned horses, a practice popularized in Argentina by top players and high‑value auctions. Critics worry gene editing could concentrate advantage among those who can pay for biotech services, and some breeders say it undermines traditional selection and mating practices.

Kheiron has said its goal is to offer options for breeding programs to improve performance, and company staff and veterinarians have described standard rearing and health checks for the foals. The five young animals will not begin routine riding until about age two and typically start sport‑specific training a year or two after that, meaning any competitive impact would occur several years from now.

Regulatory and sporting responses remain unsettled. The Argentine Polo Association's ban is in place for now, but officials have acknowledged administrative limits to detection and enforcement. Scientists said the availability of cloning and editing services is increasingly widespread and that ethical, regulatory and registration frameworks will influence how, and whether, gene‑edited horses enter competition and breeding registries in Argentina and abroad.