Cloning, embryo transfer and gene editing.

This is a reporting page. It sets out what newspapers, an encyclopedia and a rulebook say happened and what the rules are, as of October 2026. It does not judge the methods, and where sources disagree we give each version with who says it.

How common laboratory breeding is

In the Polo Argentino breed it accounts for most new horses. La Nacion (July 2024) reports that around 90 percent of recent registrations in the breed's studbook involve embryo transfer, cloning or ICSI. It counts about 8,000 embryo transfers in the prior year and roughly 300 clones in the season. The sources we read name ICSI alongside the other two methods but do not describe it, so we do not either.

Embryo transfer

Reuters notes that polo has long used surrogate mares for embryo transfer, so that the foal is carried by a mare other than its genetic mother. On La Nacion's 2024 figures, embryo transfers far outnumber clones: about 8,000 in a year against roughly 300 clones in a season.

The first polo clones

Wikipedia tells the story through Adolfo Cambiaso, the Argentine player:

• Cambiaso's stallion Aiken Cura was badly injured in the 2006 Argentine Open final and euthanised in January 2007. Live skin cells were taken at Cambiaso's request in case cloning became possible.
• Alan Meeker of Crestview Genetics, in Texas, teamed up with Cambiaso, and the first clone was produced in 2010.
• Biologist Adrian Mutto worked with Cambiaso and Ernesto Gutierrez to clone the mare Cuartetera several times.
• Wikipedia reports that a cloned horse won the Argentine championship for the first time on 7 December 2013. NeoTeo (12 December 2013) reports that the clone was Show Me, a copy of the Thoroughbred Sage, which Cambiaso rode in that year's Argentine Open final; La Dolfina won it 16-11.
• Wikipedia says Cambiaso rode clones of Cuartetera to win the 2017 Argentine Open. Inverse and Horse Illustrated, writing days after the event, place his win with six Cuartetera clones in the December 2016 Argentine Open.
• Wikipedia says the clones themselves are no longer sold, only their foals.

The lineage chart maps family links between notable polo horses, clones among them, with a source for each link.

Gene editing: the 2024 foals

Reuters (republished by KSL on 30 August 2025) reports that the Argentine company Kheiron Biotech used CRISPR to produce five foals cloned from Polo Pureza, which it calls a prize-winning horse (a mare, according to Forbes Argentina), with an edit that reduces myostatin expression to build muscle for speed. The foals were born in late 2024 at its clinic in San Antonio de Areco. Reuters described them as the world's first gene-edited horses.

The same report says Kheiron expected to produce 400 clones in 2025, which by the breeders' association's estimates would be more than half of the clones born in Argentina that year.

Forbes Argentina was summarised as reporting that the project met the requirements of Argentina's bioeconomy directorate and its agricultural biotechnology commission, CONABIA. That is a compliance claim reported from the company's side, and we saw it only as a search summary, so it could not be confirmed.

What the rules say about gene-edited horses

HPA (UK and Ireland), 2026 rules

The HPA's position is written into its rulebook. Under Rule 3b of its 2026 rules, a pony that has undergone gene editing, genome editing, genetic therapy or gene doping for competitive purposes may not play. The rule does not bar clones as such.

The HPA's 2026 club guidance also touches on cloning in one place: where a pony is euthanised at a club, any collection of samples for cloning should be done away from the club and without delays that compromise the pony's welfare.

AAP (Argentina): the sources disagree

This is the point on which the reporting conflicts, and we could not find an AAP statement to settle it.

No AAP rulebook text or AAP statement on gene-edited horses was found for this site, so we cannot say which report reflects the AAP's current rules.

USPA

No USPA rule on cloned or gene-edited mounts was found in its 2024 Outdoor Rules, which say only that a mount is a horse or pony of any breed or size. The USPA's 2026 rulebook was not reviewed; check the current book.

What we left out

Counts of Cuartetera's clones differ and have grown over time: La Nacion (May 2023) says she left more than twenty, and Popular Science (January 2026) says about 60. Other widely repeated clone counts, including how many clones a laboratory produces each year, reached us only through search summaries of press articles and could not be confirmed, so they are not given here.