Evaluation of Serum Prolactin as a Means of Pregnancy Diagnosis in Florida Manatees (Trichechus manatus latirostris)
Identification of reproductive status in the adult female Florida manatee (Trichechus manatus latirostris) can be challenging, as physical exam and diagnostic imaging are unrewarding until late gestation.2 Serum progesterone, the preferred analyte for pregnancy diagnosis in manatees, requires at least two progesterone measurements to confirm pregnancy status.2 Serum prolactin has been described as a single-sample pregnancy diagnostic for Asian (Elephas maximus) and African (Loxodonta africana) elephants, which are close relatives to manatees.1 In the present study, serum samples were analyzed from a total of 41 rescued female manatees admitted to Tampa’s Lowry Park Zoo between the years 2000 and 2016. Each sample was classified based on reproductive status as nonpregnant/nonlactating adult (n=9), pregnant (n=17), lactating (n=22), or subadult (n=7). Reproductive status was determined based on one of the following: delivery of a calf or stillborn fetus during rehabilitation, presence of a calf at rescue, presence of fetus at necropsy, visualization of fetus on ultrasound, or by confirmation of elevated progesterone levels. Statistical analysis was performed using the independent samples t-test to compare mean prolactin levels among the reproductive classification groups. Prolactin levels were significantly higher in pregnant females (17.93±24.85 ng/ml) than nonpregnant adult and subadult females (2.35±1.08 ng/ml; p=0.02). The results of this study show that serum prolactin is significantly higher in pregnant animals, supporting the potential use of this assay for pregnancy diagnosis in the Florida manatee.
The authors thank the TLPZ Florida Mammal Department staff and the Florida Fish and Wildlife Conservation Commission for their tireless efforts in manatee care and conservation.
1. Brown JL, Lehnhardt J. Secretory patterns of serum prolactin in Asian (Elaphus maximus) and African (Loxodonta africana) elephants during different reproductive states: comparison with concentrations in a noncycling African elephant. Zoo Biol. 1997;16:149–159.
2. Tripp KM, Verstegen JP, Deutsch CJ, Bonde RK, Rodriguez M, Morales B, Schmitt DL, Harr KE. Validation of a serum immunoassay to measure progesterone and diagnose pregnancy in the West Indian manatee (Trichechus manatus). Theriogenology. 2008;70:1030–1040.