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

Abstract

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 (P 4)-metabolite (allopregnanolone: 5α-P-3OH) in semi-captive females sampled randomly positively correlated with serum P 4 levels [12]. In this longitudinal study (51 weeks), we measured levels of fecal 5α-P-3OH and serum P 4 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 P 4 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 (P 4); for luteal phase 0.32–11.09 μg g −1 (5α-P-3OH) and 0.32–1.48 ng mL −1 (P 4); for pregnancy 1.41–7.38 μg g −1 (5α-P-3OH) and 0.39–1.6 ng mL −1 (P 4). A positive correlation ( t = 8.8, p < 0.01, n = 321) between levels of fecal 5α-P-3OH and serum P 4 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 P 4 values over multiple estrous cycles. This has a potential application in the reproductive management and conservation of Asian elephants.