Comparisons of Serum Progesterone and Progestagen Concentrations in Normal and Abnormal Bottlenose Dolphin (Tursiops truncatus) Pregnancies

Abstract

Although previous studies have described progesterone profiles during pregnancy in the bottlenose dolphin (Tursiops truncatus), most of these focused on normal pregnancy (NORM) or compared NORM to only one or two abnormal pregnancy types, such as abortion (AB) or perinatal loss (PNL). Hormonal pregnancy biomarker analysis from reproductive events with different outcomes may reveal differences in concentrations so that we are able to identify high risk pregnancies. The aim of this study was to describe longitudinal profiles of circulating progesterone and progestagens during reproductive events in the female bottlenose dolphin, including NORM, failure to thrive, PNL, AB, early loss (EL), and false pregnancy (FP). Progesterone differed from NORM during EL at EARLY (month post conception [MPC] 1–4), AB at MID (MPC 5–8), and FP at LATE (MPC 9–12) stages. Progestagens differed from NORM during AB and FP at MID and LATE stages and during MPC 12 in PNL and MPC 4 in EL. Progestagens may be better at predicting poor reproductive outcome in the bottlenose dolphin and a suite of hormone tests, including progesterone and progestagens, should be incorporated into existing clinical diagnostic and management practices in this species. Furthermore, analysis of multiple hormonal pregnancy biomarkers from a single sample may enable pregnancy diagnosis for wild animals.

Characterization of Circulating Androgens, Cortisol and Estrogens During Normal, Abnormal and False Pregnancy in Bottlenose Dolphins (Tursiops truncatus) Under Managed Care

“…Blood samples (n = 654: 576 samples from pregnancy or false pregnancy; 4 placental samples obtained from cord blood; and 74 samples from physiologic events) were collected from 57 animals during the period from 1983 through 2017 (Robeck et al, 2021; Table 1). These samples were collected as part of routine monitoring of animals for detection of reproductive events (n = 92).…”

“…After, the solvent layer Numbers within each classification were not compared because they do not represent all the possible reproductive events that occurred within these two populations over the study period. For a discussion of percentage typically found within each group and a more detailed analysis of reproductive outcomes with our population see Sweeney et al (2010) and Robeck et al (2021), respectively. Total number of individual animals was 57.…”

“…Although there are several studies of hormone measurements during pregnancy in bottlenose dolphins (Tursiops truncatus), the existing data are mostly comprised of pregnancies with successful outcomes, i.e., a live birth and surviving calf. Within one zoo-based population of bottlenose dolphins, the pregnancy loss and stillbirth rates are reported to be 11.5 and 5.2%, respectively (Robeck et al, 2021). Although these numbers are similar to what has been reported for other zoo-based cetaceans and domestic species (Forar et al, 1995 [domestic, cattle]; Robeck et al, 2018 [cetacean, killer whale{Orcinus orca}]), the ability to predict reproductive outcome based on hormonal biomarkers of pregnancy and then be prepared for assistance and intervention with problematic pregnancies would be tremendously beneficial for animal care husbandry and management.…”

“…Although these numbers are similar to what has been reported for other zoo-based cetaceans and domestic species (Forar et al, 1995 [domestic, cattle]; Robeck et al, 2018 [cetacean, killer whale{Orcinus orca}]), the ability to predict reproductive outcome based on hormonal biomarkers of pregnancy and then be prepared for assistance and intervention with problematic pregnancies would be tremendously beneficial for animal care husbandry and management. Evaluations of normal and abnormal pregnancy via hormone analyses have mostly relied on measurements of circulating progesterone (P4) or progestagens (PG), relaxin and thyroid hormones (Bergfelt et al, 2011(Bergfelt et al, , 2017O'Brien and Robeck, 2012;West et al, 2014;Robeck et al, 2021). These studies provide valuable information regarding pregnancy related hormone dynamics for successful pregnancies, stillbirths, abortions, and early embryonic loss.…”

“…In the killer whale, a study comparing circulating PGs and relaxin during pregnancies with different outcomes as well as false pregnancy and estrus represents one of the most thorough examinations of several different reproductive outcomes via longitudinal reproductive hormone monitoring in cetaceans (Robeck et al, 2018). We have recently conducted a similar study of P4 and PGs in the bottlenose dolphin (Robeck et al, 2021). Past studies of reproductive hormone profiles during normal bottlenose dolphin pregnancy have provided reference ranges that can be used to assess other pregnancy types, such as stillbirth, abortion or early embryonic loss (Bergfelt et al, 2011(Bergfelt et al, , 2017O'Brien and Robeck, 2012;West et al, 2014).…”