Genetic variability of semen freezability in the Purebred Spanish horse

Project led by Mercedes Valera of the MERAGEN group of the Department of Genetics, shared between the University of Seville and the Faculty of Veterinary Medicine of the University of Córdoba.

Keeping cryopreserved semen doses in the equine species has advantages over fresh semen: it preserves a stallion's fertilising capacity in the long term, even after his death, and enables rational, controlled national and international trade in germplasm, used at the right moment according to the mare's reproductive characteristics. However, stallions differ markedly in how well their sperm freezes.

These differences are mainly genetic (breed and individual) and sometimes require the freezing protocol and extender to be adapted to each stallion. Despite previous research, there is still no predictive test to detect a horse's "semen freezability" early. Fertilising capacity may also decline over years of cryopreservation in liquid nitrogen.

In the Purebred Spanish horse, where frozen semen is routinely used and official semen germplasm banks have been created, standardised and validated analytical protocols are needed as a tool for controlling and certifying the practices of reproduction centres.