Trends in reproductive technology use in the American Quarter Horse (AQHA)

Abstract

The acceptance of reproductive technology by a breed association is dependent on the cost of the procedure, interest in the technology by the breeder as well as the safety and efficacy of the procedure. The AQHA is the largest Breed Registry in the world with 3.1 million registered horses in 2023 and is an example of a registry that has embraced nearly all types of assisted reproduction techniques that have been developed. The AQHA registered 86,762 foals in 2023; 70,526 of these foals were born in the USA and 16,162 foals were born outside the USA. Approximately 8,500 AQHA registered foals were born in Europe, with the remaining international foals born primarily in Canada and Mexico. A significant number of Quarter Horse foals in Australia and South American countries were conceived by frozen semen exported from AQHA registered stallions standing in the US. These countries maintain their own Quarter Horse registries and therefore those foals are not reflected in the AQHA registry data. Data were obtained from the AQHA on the number of registered foals produced each year from embryo transfer (fresh and shipped embryos), frozen embryos, transported cooled and frozen semen. According to the AQHA data, the first foal registered by embryo transfer was in 1981. The number produced remained relatively low until the year 2000, when registrations increased dramatically to over 6000 in 2023. This was due in part to the development of commercial flushing and storage medias that allowed embryos to be collected on the farm and sent to large recipient stations for transfer. The first frozen/thawed embryo registered by AQHA was in 2012 and the numbers have only recently increased to 300-400 per year. Since in vivo derived embryos do not survive freezing and thawing very well (unless smaller than 300 microns), the vast majority of frozen embryos are derived by intracytoplasmic sperm injection (ICSI) and vitrified. Recently, ICSI has become accepted as a technique for in vitro embryo production and has been embraced by breeders, however AQHA does not currently collect data on the number of foals produced by ICSI. The first registered foal from cooled transported semen was in 1997 and the first from frozen semen occurred in 2000. The use of cooled transported semen increased dramatically to where about 14,000 foals are registered each year from the use of transported semen. It continues to be the procedure of choice, but the numbers of foals from frozen semen have increased over the past 15 years to where now 32% of foals from transported semen were sired by frozen semen. Through education and improvement in cryopreservation techniques and breeding strategies, frozen semen has been more widely accepted. AQHA has set restrictions on the use of certain technologies. For example, for stallions born after 2015 there is a limit on the use of frozen semen beyond 2 years following death.