Application of an enzyme-immunoassay (EIA) for rapid screening of 5 alpha-pregnane-3,20-dione (DHP) in blood plasma of the Asian elephant, Elephas maximus

Populations of African (Loxodonta africana) and Asian Elephants (Elephas ma ximus) in toes and safari parks are at risk due to their low reproductive s uccess. To extend the limited knowledge of their reproductive physiology, t he development of easy and practical methods for the analysis of the releva nt reproductive hormones is essential to support e,g. assisted reproduction . For the measurement of 5 alpha -pregnane-3,20-dione (DHP), the predominan t ovarian gestagen in both species, an enzyme-immunoassay (EIA) based on co mmercial reagents was applied. Advantages of this EIA are the small volume of plasma needed for evaluation (5 mul) and the possibility of direct proce ssing without an extraction stage. The lower limit of detection was 0.16 ng /ml, the mean recovery was 101% and the mean coefficients of variation were 7.3% (intra-assay) and 9.9% (inter-assay). In Asian elephants, DHP levels reached 15 ng/ml during the luteal phase and up to 21 ng/ml during pregnanc y. Estrous cycle lengths based on the lowest DHP concentrations varied from 12 to 20 weeks (mean 15.4 +/- 2.3). In two Asian elephant cows a calf was still-borne. Thereafter, the animals reassumed ovarian activity after appro ximately 8 and 13 weeks, respectively. In one animal estradiol implants for hormonal contraception caused a down regulation of the ovarian function as demonstrated by an irregular pattern of DHP secretion over a period of 48 weeks. We propose the direct DHP-EIA as a suitable method for reproductive monitoring in elephants, as it can be easily established in laboratories.