Abstract
The physiological demands of pregnancy inevitably result in alterations in both biochemical and hematological parameters as fetal development occurs. The shifts observed in successful pregnancy in bottlenose dolphins Tursiops truncatus to support both fetal physiological needs and maternal basal requirements have been established according to each trimester. Detecting aberrations in blood-based biomarkers could help facilitate diagnosis of gestational abnormalities, improve our understanding of factors influencing reproductive outcomes and aid in prediction of reproductive failure. This study retrospectively analyzed 263 blood samples from 15 bottlenose dolphins in 21 failed pregnancies over 28 yr (1989-2017). Most samples remained within normal pregnancy reference ranges; however, significant shifts were observed between trimesters. Hematological alterations, compared to successful pregnancy reference ranges from previously published data, were consistent across failed pregnancies and included an increased prevalence of elevated 2nd and 3rd trimester neutrophils, elevated 2nd trimester monocytes and decreased 3rd trimester eosinophils. In addition, low hematocrit and low red blood cells were more prevalent in the 2nd trimester. Biochemical shifts included an increased prevalence of elevated creatine phosphokinase in the 3rd trimester outside of the normal reference ranges. Across failed pregnancies, calcium and iron were decreased in the 3rd trimester. Significantly decreased progesterone in the 3rd trimester was a negative prognostic indicator of pregnancy outcome with decreasing 3rd trimester progesterone associated with failed pregnancy. This study demonstrates the use of blood-based biomarkers as possible predictors of pregnancy outcome in bottlenose dolphins.
Highlights
Blood-based biomarkers can be used diagnostically as an aid to predict pregnancy outcome and direct mitigation strategies to negate pregnancy loss (Pavord & Hunt 2018, Memtsa et al 2019)
Neonatal survival rates as high as 83% have been reported in Sarasota Bay, Florida, with success defined as pregnancy diagnosis confirmed with a live birth
In the northern Gulf of Mexico, dolphins impacted by the Deepwater Horizon oil spill have reproductive success rates as low as 19.4% (7/36), with success defined as observing a calf up to 1 yr post-pregnancy diagnosis (Kellar et al 2017)
Summary
Blood-based biomarkers can be used diagnostically as an aid to predict pregnancy outcome and direct mitigation strategies to negate pregnancy loss (Pavord & Hunt 2018, Memtsa et al 2019). Neonatal survival rates as high as 83% have been reported in Sarasota Bay, Florida, with success defined as pregnancy diagnosis confirmed with a live birth. A combined survival rate of 64.7% (22/34) has been documented among several southeastern US populations, with success defined as observing a calf up to 1 yr post-pregnancy diagnosis (Wells et al 2014, Kellar et al 2017). In the northern Gulf of Mexico, dolphins impacted by the Deepwater Horizon oil spill have reproductive success rates as low as 19.4% (7/36), with success defined as observing a calf up to 1 yr post-pregnancy diagnosis (Kellar et al 2017). Identifying factors which could influence reproductive success is important in understanding demographic and population dynamics for conservation management of wild dolphin populations (Schwacke et al 2017)
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