Semen Cryopreservation and Transcervical Insemination in the Mexican Gray Wolf (Canis lupus baileyi)
Successful captive breeding is essential to recovery of Mexican gray wolves (Canis lupus baileyi). The long-term monogamous mating system of wolves, the fact that not all SSP-assigned pairs reproduce, agency restrictions on human contact, and prohibition of surgical insemination present challenges for captive reproduction. Our objectives were to improve sperm longevity and develop transcervical insemination (TCI) using generic grey wolves and domestic dogs as models. Longevity of sperm (collected by electro-ejaculation) was not significantly different over 24 hours between generic gray wolves and domestic dogs, but semen collected from dogs by manual stimulation had prolonged motility (p<0.05), suggesting increased exposure to prostatic fluid in electro-ejaculated samples may affect longevity. Semen from six generic gray wolves was extended in three commercial semen extenders (CaniProTM Chill 5, Minitube of America, Verona, WI; Fresh Express®, Synbiotics, Kansas City, MO; Kenney Formula, Reproduction Resources, Walworth, WI) or a traditional tris-based extender. At 24 hours, progressive sperm motility was highest (p<0.05) in Fresh Express® and CaniProTM Chill 5 extenders. In a different experiment, semen samples collected from six generic gray wolves via electroejaculation were either immediately centrifuged and then suspended in semen extender (traditional protocol), or immediately diluted in semen extender and then centrifuged to reduce exposure to prostatic fluid. There was no significant difference between the two methods. When semen was manually collected from two generic gray wolves and placed in these extenders, progressive motility (assessed over 24 hours) appeared better in Fresh Express®. Furthermore, to maximize fertility with frozen-thawed semen, endoscopic TCI, used routinely in domestic dogs, is being developed for the Mexican gray wolf.