17 WHITETAIL DEER OFFSPRING FROM ARTIFICIAL INSEMINATION WITH EPIDIDYMAL SPERM HARVESTED FROM A HUNTER-KILLED BUCK

Abstract

The ability to cryopreserve epididymal sperm from mature postmortem bucks has long been of interest to both wildlife conservationists and deer ranchers. At present, there is loss of valuable genetics from the hunter harvest of trophy males. Increasing adult body weight and antler size of adult males would be of substantial economic value to the deer hunting industry. In this preliminary trial, 6 yearling pen-raised Whitetail does (47 to 58 kg), in good body condition, were isolated from all bucks prior to the onset of the fall breeding season. Females were synchronized for AI with a 14-day caprine CIDR and 200 IU of eCG (IM) at the time of CIDR removal. Does were timed AI 60 to 63 h after eCG with one 0.5-mL straw of frozen–thawed Whitetail sperm. All sperm used for AI were harvested from a single mature Whitetail buck that was hunter harvested during the previous hunting season. Within 3 h after death, the testes with scrotum were removed, enclosed in a plastic Ziploc bag, and then placed in a Styrofoam ice chest containing frozen cold packs. The ice chest was transported to the laboratory where sperm were extracted at 4°C in the late evening (<12 h postmortem) by flushing the cauda epididymides with Triladyl^® one-step extender (Minitube, Verona, WI, USA) in a retrograde flow from a small incision made in the cauda. The sperm–Triladyl mixture was flushed from the cauda incision into a sterile 50-mL tube using a 10-mL plastic syringe modified by heating and then stretching the tip until small enough to thread into the vas deferens. The sperm plus extender was then held at 4 to 10°C for 12 h and frozen at a concentration of <50 million/straw using a commercial bull freezing protocol (Genex Custom Collection Center, Baton Rouge, LA, USA). A random sample of straws was then thawed, resulting in an overall post-thaw motility of 60%. The remaining straws were left frozen in liquid nitrogen until the next breeding season. On the first of December, does (n = 6) were given 0.1 mL of Domosedan^® (Pfizer Animal Health, Groton, CT, USA) IV and inseminated transcervically using a modified caprine speculum. All does were handled in a custom-built deer barn, and AI was performed by one technician in a drop-bottom deer chute (Deer Handler; Delclayna, Alberta, Canada). At 48 days after AI, 3 of the 6 does (50%) were diagnosed pregnant by transrectal ultrasonography. All pregnant females gave birth, producing 5 offspring (1 male and 1 female singletons and a set of mixed sex triplets) that ranged from 1.9 to 4.3 kg and had a mean gestation length of 196 days (range = 190–203 days). In summary, results indicate that live offspring can be produced from epididymal sperm harvested from mature hunter-harvested Whitetail bucks. Further experiments are needed to optimize techniques and protocols for the harvesting and usage of these gametes.