Ultrasonographic evaluation of the effects of exogenous gonadotropins on follicular recruitment and ovulation induction in the Atlantic bottlenose dolphin (Tursiops truncatus).
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Transabdominal ultrasonography and serum steroid concentrations were used to evaluate the effects of exogenous gonadotropin administration on ovarian activity of two anestrous bottlenose dolphins (Tursiops truncatus). The gonadotropin used for follicular recruitment was PG600, which has 400 IU equine chorionic gonadotropin (eCG) and 200 IU human chorionic gonadotropin (hCG) activity per 5 ml. Ovulation induction was attempted with hCG. PG600 was administered in two doses of 20 ml (1,600 IU eCG and 800 IU hCG) and 12.5 ml (1,000 IU eCG and 500 IU hCG), respectively, 48 hr apart on days 0 and 2. On day 6, 1,500 IU of hCG was administered. Progesterone and total immunoreactive estrogens were determined before and after the gonadotropin administration. Bilateral ovarian ultrasonographic exams were performed daily on days 4-9 and on day 22. Serum immunoreactive estrogen concentrations were greater than the pretreatment concentrations after day 4 for both dolphins and remained elevated for the rest of the study. Serum progesterone concentrations rose above 1 ng/ml 2 days after hCG treatment and remained elevated for the rest of the study. Small antral follicles (< 0.5 cm) were initially observed bilaterally in both dolphins on day 4. In both animals on day 9, there were > 12 follicles/ovary, ranging from 0.5 to 1.5 cm. By day 22, the multiple follicles ranged from 0.5 to 4.5 cm in diameter. No ultrasonographic evidence of luteal formation was observed. The results indicate that 1) transabdominal ultrasonography can be used to detect and follow follicle growth in bottlenose dolphins; 2) bottlenose dolphins are sensitive to exogenous gonadotropins (multiple follicular recruitment of follicles occurred); and 3) until further ultrasonographic studies can be conducted to evaluate the effects of titrated doses of exogenous gonadotropins, these protocols should be considered unsuitable for ovulation induction.