Estrus Prediction with a Novel Luteinizing Hormone Assay in Two Delphinid Species
Reproduction management is a key goal for United States aquaria holding marine cetaceans, in order to improve stock levels and quality. To ensure breeding pairs are matched according to aquaria needs, and that reproduction is synchronized, managers at many facilities have developed numerous methods to accurately and rapidly track ovulation and estrous cycling, in order to plan natural-service breeding or artificial insemination programs. Five aquaria have successfully implemented artificial insemination and other advance reproductive technology programs for Orcinus orca and Tursiops truncatus, and three facilities have begun implementing artificial insemination for Lagenorhynchus obliquidens.
In this study, three physical methods for predicting ovulation were compared with three endocrinological methods, including a novel enzyme-linked immunoassay (ELISA) for luteinizing hormone (LH) developed for this study, in two T. truncatus and two L. obliquidens. Female reproductive behavior, cyclical changes in vaginal mucus and follicular and tract imaging (with ultrasonography and endoscopy) were compared to the reproductive cycling of progesterone (P4), estrogen metabolites (E2), and LH. Standard radioimmunoassays (RIA) were employed to follow P4 and E2. An RIA utilizing a well-characterized anti-bovine LH antibody, 518β7, was employed for the study by the Roser Lab at the University of California at Davis. 518β7 was used to develop a novel ELISA for LH, the results of which were further compared with employment of a previously described canine enzyme immunoassay (EIA) in the T. truncatus. Ultrasound was used as the definitive means of characterizing follicular cycling and estrus. Behavioral and vaginal tract changes correlated well, but with a high degree of individual variation, with changes in follicular size and approaching ovulation. It was concluded that managed reproduction is best conducted by combining physical means of predicting ovulation and an assay for luteinizing hormone. P4 cycling was successfully used to confirm ovulation and as an early predictor of successful insemination. E2 cycling matched results from previous studies that showed strong correlation between approaching estrus and a rise in E2. All three LH assays were strongly correlated to the onset of estrus as represented by an LH peak. The LH-RIA gave the most accurate results followed by the ELISA. The LH-EIA showed the greatest variability, but was useful as a ready, bench-top measurement. The addition of the ELISA developed for this study may prove a useful tool for reproductive managers, and will continue to be refined for ready use.