Assessment of estrus cyclicity in the Asian elephant (Elephas maximus) by measurement of fecal progesterone metabolite 5α-P-3OH, using a non-invasive assay

Reproductive management of the Asian elephant (Elephas maximus) is important for its conservation. To monitor its estrous cyclicity, we earlier used an indirect ELISA to show that levels of fecal progesterone (P4)-metabolite (allopregnanolone: 5α-P-3OH) in semi-captive females sampled randomly positively correlated with serum P4 levels [12]. In this longitudinal study (51 weeks), we measured levels of fecal 5α-P-3OH and serum P4 in seven semi-captive female elephants. Females exhibited three types of hormonal profiles. Four females showed cyclical patterns of fecal 5α-P-3OH and serum P4 typical of normal estrous cycles, two showed acyclic pattern while one showed high values indicative of a pregnant animal. Values for anestrous or follicular phases were ⩽0.3 μg g−1 (5α-P-3OH) and ⩽0.3 ng mL−1 (P4); for luteal phase 0.32–11.09 μg g−1 (5α-P-3OH) and 0.32–1.48 ng mL−1 (P4); for pregnancy 1.41–7.38 μg g−1 (5α-P-3OH) and 0.39–1.6 ng mL−1 (P4). A positive correlation (t = 8.8, p < 0.01, n = 321) between levels of fecal 5α-P-3OH and serum P4 was observed. A random sample of 30 free-ranging female elephants showed fecal 5α-P-3OH values of 0.06–23.4 μg g−1, indicating them to be in different stages of estrous cyclicity. This study is the first to assess the reproductive phases of female Asian elephants based on the correlative-patterns of both the fecal 5α-P-3OH and serum P4 values over multiple estrous cycles. This has a potential application in the reproductive management and conservation of Asian elephants.

► Serum P4 and fecal 5α-P-3OH measured in semi-captive and free-ranging female Asian elephants.
► Semi-captive females exhibited three different hormonal profiles – cycling, non-cycling and pregnant.
► Significant correlation between measured levels of serum P4 and fecal 5α-P-3OH was observed.
► Varied levels of fecal 5α-P-3OH were measured in a random sample of free-ranging females, indicating them to be cycling.
► Measurement of fecal 5α-P-3OH is a useful tool in the management and conservation of captive and free-ranging Asian elephants.