Reproductive Physiology and Development of Artificial Insemination Technology in Killer Whales (Orcinus orca)1
Biology of Reproduction
Research was conducted to define the basic reproductive physiology of killer whales, Orcinus orca, and to use this knowledge to facilitate the development of artificial insemination procedures. The specific objectives were to: i) determine the excretory dynamics of urinary LH and ovarian steroid metabolites during the estrous cycle; (ii) evaluate the effect of an exogenously administered synthetic progesterone analog on reproductive hormone excretion; (iii) validate the use of transabdominal
... f transabdominal ultrasound for ovarian evaluation and timing of ovulation; (iv) examine the quality of semen after liquid storage and cryopreservation, and (v) develop an intrauterine insemination technique. Based on urinary endocrine monitoring of 41 follicular phases and 26 complete cycles from five females, estrous cycles were 41 d long, comprised of a 17 d and 21 d follicular and luteal phase, respectively. A consistent temporal relationship was observed between peak estrogen conjugates (iEC) and the LH surge, which occurred ~0.5 d later. Two animals placed on oral altrenogest (3 separate occasions for 30, 17 and 31 d, respectively) excreted peak urinary estrogen concentrations 25 d post-withdrawal that were followed by sustained elevations in urinary pregnanediol-3α-glucuronide (iPdG) excretion. Mean preovulatory follicle diameter was 3.9 cm (n = 6) and ovulation occurred 38 h (n = 5) after the peak of the LH surge. Based on visual estimates of motility, liquid stored semen maintained 92% of its raw ejaculate sperm motility index (SMI = total progressive motility x kinetic rating (0-5 scale, 0 = no movement, 5 = rapid progressive movement) when held at 4 o C for 3 d post-collection. Semen cryopreserved using a medium freezing rate demonstrated good post-thaw total motility (50.3%), progressive motility (94%) and kinetic rating (3.5 out of 5). Insemination during 8 estrous cycles resulted in three pregnancies (38%), 2 from liquid stored and one from cryopreserved semen. Two calves were delivered after gestation lengths of 552 and 554 d, respectively. These data demonstrate the potential of noninvasive endocrine monitoring combined with serial ultrasonography for improving our understanding of the reproductive biology of cetaceans. This fundamental knowledge was essential for ensuring the first successful conceptions, resulting in live offspring, using AI in any cetacean species.