ABSTRACT
Nowadays, stallion semen processing and preservation for artificial insemination (AI) is a widely used tool in modern horse reproduction. During the 20th century, AI had a strong development in most domestic animal species except in equine species, due to economic interests, traditional aspects and mistrust of horse owners. Semen conservation technologies based on temperature decrease to reduce or stop sperm metabolism are necessary to increase the lifespan of sperm and preserving sperm functionality and fertility. Currently, AI is performed mainly with fresh, chilled or frozen semen. Sperm refrigeration at 5ºC has several advantages related to easy handling and shipping, low cost because it does not require special equipment and minor legal requirements for import and export. However, cryopreservation is the only viable method for spermatozoa storage during indefinite periods. The main problem of freezing semen is related to the low fertility rates obtained due to wide inter-individual sperm quality variability; therefore only some stallions produce suitable semen for cryopreservation. To solve these disadvantages, new methodologies have 228been studied during recent years with different results. Vitrification and lyophilization are promising stallion semen preservation techniques that require further study to be applied routinely during long-term periods.
