Variation of Fecal Progesterone Concentration in Captive Female Bottlenose Dolphins (Tursiops truncatus)
The detection of hormones in fecal samples has been used during the last decade in many different domestic and exotic species, including humans, to develop a method that is less invasive than blood collection to monitor hormonal levels. The aim of the present study was to develop an immunoassay to measure fecal progesterone in order to monitor ovarian activity in bottlenose dolphins.
Samples of feces (N=314) were collected at least once a week over the period of one year from three females with ages ranging from pre-pubertal to sexual maturity, and one pregnant female from the seventh month of gestation until parturition. Samples were kept in plastic tubes and frozen at minus 23 degrees Celsius until the time of analysis, carried out using radioimmunoassay (RIA) techniques. The progesterone (P4) RIA method underwent validation (recovery and parallelism) tests. For the three females of uncertain reproductive status, blood samples were collected at least once a month in an attempt to evaluate the pattern between known data from the serum and unknown results of fecal samples. When possible, vaginal cytology (N=392) and ultrasound examination were used as additional method to monitor the ovarian activity of the three non-pregnant females.
In pre-pubertal females, fecal P4 ranged between 0.35 and 11.21 pmol/g feces. A positive correlation was found between plasma and fecal progesterone (R=0.783, P<0.001). When one pubertal female began to show ovarian activity (detected with an increase in P4 in the serum and changes in the vaginal cytology), fecal P4 ranged between 0.43 and 46.25 pmol/g feces. Vaginal cytology showed an increased basal and parabasal cell number associated with increased P4 values. Superficial cells decreased while fecal P4 increased, and the luteal phase length was estimated to be 6-12 days. A negative correlation was observed between fecal P4 and superficial cells (R=-0.283, P<0.01), and between serum P4 and superficial cells (R= -0.303, P=0.061). When follicles were seen on ultrasound examination (5-14 mm), fecal P4 was lower than 10 pmol/g feces, and the observed values were assumed to be indicative of the follicular phase. However, it was not possible to estimate the follicular phase length. In the pregnant female, fecal progesterone ranged between 26.99 and 176.92 pmol/g feces, and this concentration interval was considered indicative of a fully active corpus luteum. Fecal progesterone dropped to 1.74 pmol/g feces within a week after parturition.
These preliminary results indicate that it is possible to monitor the ovarian activity of the bottlenose dolphins using fecal P4 measurement. More research is needed to further investigate the relationships between fecal P4 and other diagnostic tools such as ultrasonography and vaginal cytology.
The authors would like to thank Dr. Ana Salbany, Dr. Luis Roque and all the trainers of Mediterraneo Marine Park (Malta) and Zoomarine (Portugal) for the samples collection. Special thanks to Dr. Fiona Brook and The Hong Kong Polytechnic University for providing the Sonosite Ultrasound machine and all the support.