PREGNANCY DETERMINATION IN THE ASIAN ELEPHANT (ELEPHAS-MAXIMUS) - A CHANGE IN THE PLASMA PROGESTERONE TO 17-ALPHA HYDROXYPROGESTERONE RATIO

The measurement of circulating progesterone (P) is widely used to conf irm and monitor pregnancy in the captive Asian elephant. Consistently elevated progesterone (P) concentrations for a minimum of 12 weeks can be used as a positive indication of pregnancy, although two instances of prolonged P secretion during the cycle have been recorded [Rubel, 1987; Olsen et al., 1994]. Previously, we demonstrated that pregnanetr iol was the major urinary gestagen metabolite enabling the noninvasive monitoring of the reproductive cycle of the Asian elephant [Niemuller et al., 1993] as well as pregnancy [unpublished data]. The importance of this unusual urinary metabolite triggered an investigation into th e secretion of circulating concentrations of 17 alpha hydroxyprogester one (17 alpha OHP) during pregnancy and reproductive cycles, as this s teroid is the only steroid precursor of pregnanetriol. Comparison of t he profiles between 17 alpha OHP and P during early pregnancy (n = 5) and nonconceptive cycles (n = 15) demonstrated a decline in 17 alpha O HP, but not P, as early as week 3 postmating (designated as week 1) an d lasting up to week 13. Otherwise, secretions of 17 alpha OHP mimicke d P concentrations throughout pregnancy and in nonconceptive cycles. E xamination of the mean ratio values of 17 alpha OHP to P demonstrated a significant drop in the ratio during weeks 2-7 of early pregnancy fr om greater than or equal to 0.7 to <0.7 compared with the same time pe riod in a nonconceptive cycle (P < 0.05, N = 5). A 2x2 table analysis of the 17 alpha OHP:P ratio during weeks 2-7 indicated that the possib ility of a false positive or false negative result was 3.4 and 6.5%, r espectively, based on the sensitivity and specificity of the test. Ove rall, gestation lengths of the preg nancies completed during this stud y (N = 4) ranged from 91 to 98 weeks, with a mean of 93.6 +/- 2.9 (SEM ) weeks. A birth-to-conception interval of 47 weeks was noted in one a nimal. The results described in this report provide additional data on the reproductive endocrinology of the pregnant Asian elephant and als o present the earliest means to date of determining pregnancy by analy sis of the 17 alpha OHP:P ratio. (C) 1997 Wiley-Liss, Inc.