Novel genetic material must often be introduced into otherwise closed captive and wild animal populations to avoid the potentially deleterious consequences of inbreeding depression, and low genetic variability. However, moving animals between populations poses risks to the health and welfare of animals that are moved, risks the transfer of pathogens and has financial implications. Artificial insemination can be an effective means to introduce genetic material while minimizing these disadvantages. However, the success rates of artificial insemination (AI) are generally much lower than that of natural matings. The procedure is also more expensive and can be complicated and risky.
Estrus detection can be the most important factor influencing AI efficiency.1 Ultrasonography has been shown to be a non-invasive and reliable method of monitoring the estrous cycle in the dolphin, for example, ovarian follicular development, ovulation and development of the corpus luteum,2,3 therefore can be effective in determining the optimum time to inseminate. Another variable influencing the success of conception after AI, includes semen quality. Fresh semen is typically superior to thawed frozen semen,4,5 but cannot be stored for long. Cryopreserved semen offers the ability to fertilize female dolphins far removed from the donor male geographically and temporally. Where semen is deposited in the female reproductive tract may also affect the success of AI.
Five female Tursiops aduncus were inseminated between March 2000 and December 2003 with freshly extended or cryopreserved semen collected from Tursiop aduncus males at Ocean Park, Hong Kong. A total of eleven sequences of inseminations (ranging from one to eight inseminations per anticipated ovulation) were performed. Three pregnancies resulted from these inseminations. Female dolphins were generally sedated for the AI procedure. They were presented in lateral recumbency on a moist mattress. After disinfection of the region around the genital slit, a disinfected 160 cm Olympus gastroscope attached to a video system was inserted into the vagina. The pseudocervix was visualized, in most cases, and a catheter was fed through the operating channel of the gastroscope and manipulated to attempt passage of the tip of the catheter into the spermathecal recess. Semen was then deposited via the catheter into this recess, when possible, and the dolphin returned into the water. On two occasions, however, the gastroscope was introduced directly into the uterine body and horns. Simple changes in positioning of the female and the use of insufflation appeared to improve access to the cervix.
The authors are grateful to Wendy Chan for technical assistance; Gary Wong, Harriet Chiu and the rest of the Marine Mammal Department for their invaluable help with dolphin training, husbandry and handling; Hui Suk Wai, Mickie Cheung and the rest of the Clinical Laboratory staff for assistance with semen processing; and Queeny Yeun for her assistance with semen collection and semen processing.
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