Hysteroscopic or rectally guided, deep-uterine insemination of mares with spermatozoa stored 18 h at either 5 °C or 15 °C prior to flow-cytometric sorting

Practical application of sex-selected spermatozoa in the horse industry would be greatly improved by the ability to develop simplified methods for shipping, storing, and inseminating sex-selected spermatozoa. Acceptable pregnancy rates have been achieved using fresh sex-sorted stallion sperm, however many stallion owners are reluctant to send their stallions to the sorter location for collection during the breeding season. Furthermore, the technology would be more applicable if the hysteroscopic insemination technique was not necessary for adequate pregnancy rates. Hysteroscopic insemination requires expensive equipment and specially trained personnel. In the present study, stallion sperm were sex-sorted after being stored at either 5 °C or 15 °C for 18 h. Twenty million sex-sorted sperm were then inseminated using one of two insemination techniques: the hysteroscopic method or the rectally guided, deep-uterine technique. Results were determined based on 16-day pregnancy status. A first-cycle pregnancy rate of 72% (18/25) was achieved when sperm were shipped at 15 °C, sex-sorted, and then inseminated using the hysteroscopic method. With these results, it can be concluded that stallions are not necessary at the sorter location to achieve acceptable fertility with sex-sorted sperm. There was a tendency for more mares to become pregnant when sperm were shipped at 15 °C prior to sorting, when compared to shipment at 5 °C. Similarly, there was a tendency for more mares to become pregnant when hysteroscopic insemination was utilized, when compared to the rectally guided, deep-uterine technique. These trends suggest that if larger group numbers were available, significant differences between the treatments may be revealed.