Sattler R, Bishop A, Woodie K, Polasek L. Characterizing estrus by trans-abdominal ultrasounds, fecal estrone-3-glucuronide, and vaginal cytology in the Steller sea lion (Eumetopias jubatus). Theriogenology 120:25-32. https://doi.org/10.1016/j.theriogenology.2018.07.020
Abstract:
The
ability to monitor the estrus cycle in wild and captive marine species is
important for identifying reproductive failures, ensuring a successful breeding
program, and monitoring animal welfare. Minimally invasive sampling methods to
monitor estrus in captive populations have been developed, but results suggest
these tools can be species-specific in their precision and accuracy. Therefore,
the minimally invasive sampling methods of trans-abdominal ultrasounds, a fecal
steroid analysis (estrone-3-glucuronide, E1G), and vaginal cytology, were
evaluated for their efficacy to characterize and monitor estrus in a captive
breeding population of Steller sea lions (Eumetopias
jubatus). Three adult females were sampled over five breeding seasons,
resulting in six estrus profiles characterized by trans-abdominal ultrasounds, five
by fecal E1G, and four by vaginal cytology. Animals were trained to allow
trans-abdominal ultrasounds, fecal samples, and vaginal swabs to be collected approximately
daily. Of the 76 trans-abdominal ultrasound sessions attempted, 8 successfully
visualized both ovaries. From these scans, the chronology of ovarian changes
during proestrus and estrus was estimated. The time from the detection of developing
follicles to the identification of a dominate follicle occurred in 2-5 days and
a corpus hemorrhagicum formed approximately 4 days later. However, because
visualization of the ovaries was prevented by the gastrointestinal system in 88%
of scans, this tool was overall unreliable for monitoring changes associated
with estrus. To detect fine scale physiological changes associated with estrus,
we analyzed changes in fecal E1G (n = 62) and vaginal cytology (n = 157) 15
days before and after each female’s single copulation event (Day = 0). Changes
in fecal E1G had the highest accuracy at detecting Day = 0. Fecal E1G increased
leading up to estrus, peaked at Day = 0, and then declined. Although we did
observe the characteristic increase in superficial cells associated with
impending estrus, the type of cell which peaked closest to Day = 0 was
intermediate. The uncertainty around the peak in intermediate cells, indicating
estrus, was greater than the uncertainty associated with detecting estrus from
fecal E1G. Collectively, these results suggest that changes in fecal E1G and
vaginal cytology are viable tools to detect estrus in Steller sea lions, but
require daily sampling to detect gradual changes, limiting their applicability
to studies of wild populations.
Please email me for a copy of the pdf.
renaes@alaskasealife.org
Thanks!
Renae Sattler
Research Associate
Alaska SeaLife Center
Seward, AK 99664
907-224-6882