Identification of Fecal Sex Steroid Metabolites and Evaluation of Ovarian Cycle and Pregnancy in Somali Wild Ass (Equus africanus somaliensis)

Abstract

This study aimed to establish a noninvasive method for monitoring reproductive endocrinology in a female Somali wild ass (Equus africanus somaliensis). Enzyme immunoassays (EIA) using progesterone (P 4 ), estradiol-17β (E 2 ) and estrone (E 1 ) antisera were used to analyze fecal progestagens and estrogens. Then, fecal steroid metabolites of different pregnancy stages were identified by a combination of high performance liquid chromatography (HPLC) and EIA. The change in fecal progestagens showed ovarian cyclicity, but estrogens showed no distinct changes during non-pregnancy.Based on the profile of progestagen concentration, it was calculated that an average (±SD) ovarian cycle was 22.7± 2.9 days. Fecal progestagen levels were fluctuated throughout the pregnancy, sharply increasing on the 67th and 347th days of pregnancy, and the maximum concentration occurred just before parturition (stillbirth). The estimated gestation period by the progestagen profile was 390 days. Estrogen levels also sharply increased from the 95th day of pregnancy, reached a peak in the middle of pregnancy, and then gradually decreased until approaching parturition (stillbirth). 5 α-Pregnane-3β-ol-20-one, 5α-pregnan-3, 20-dione, E 2 and E 1 were mainly detected in feces throughout the pregnancy.The results indicated that the excretion pattern of 5α-pregnane-3β-ol-20-one and 5α-pregnan-3,20-dione detected in feces is effective for monitoring the ovarian cycle and pregnancy, and the profiles of fecal E 2 and E 1 reflect the endocrine function of fetoplacental units.