Studies were conducted to determine: 1) if fecal hormone metabolite concentrations correlated with serum estrogen and progesterone concentrations, follicular activity and reproductive behavior in the black rhinoceros (Diceros bicornis) and 2) if threshold values of respective fecal metabolite concentrations correlated with pregnancy. Blood and fecal samples were collected, in conjunction with transrectal ultrasound and behavior observations, for an 18-month period from one black rhinoceros female. Subsequently, serial fecal samples were collected from 13 females in 10 zoos. Quantitative analysis of serum progesterone (P 4 ) and estradiol (E 2 ) was performed by radioimmunoassay (RIA); analysis of fecal estrogen metabolites (E) and fecal progesterone metabolites (P) were performed by enzyme immunoassay (EIA). Serum P 4 concentrations identified two luteal phase patterns and two nadirs which corresponded with behavioral estrus. Fecal E patterns indicated a sharp peak which corresponded with breeding. Concentrations of fecal P illustrated identifiable nadirs and several peaks which corresponded to serum P 4 nadirs and luteal phases. Serum P 4 concentrations were not different between the luteal phase and pregnancy. Fecal P concentrations started to rise above luteal phase concentrations approximately 150 days postbreeding and remained elevated until immediately before parturition. Serum E 2 and fecal E concentrations rose and subsequently declined after parturition. In the fecal samples from seven pregnant females, fecal P concentrations were similarly elevated compared to six nonpregnant females. Results indicated that fecal steroid metabolites accurately reflected serum steroid hormone concentrations and that the measurement of P and E concentrations permitted the characterization of the estrous cycle, the diagnosis of pregnancy, and the onset of parturition.
We validated fecal metabolite analysis as a noninvasive means of diagnosing pregnancy in uncaptured, free-ranging Rocky Mountain elk (Cervus elaphus nelsoni). During November 1991, we collected blood samples from 21 radiocollared, 1- to 10-year-old female elk in Yellowstone National Park, Wyoming (USA), and determined their pregnancy status by radioimmunoassay of serum pregnancy specific protein B and serum progesterone concentrations. From December 1991 through April 1992, we collected three to 12 fecal samples from each collared elk and measured the concentration of estrone conjugates, pregnanediol-3-glucuronide, and free progesterone by enzyme immunoassays. We also evaluated fecal samples from 10 unmarked male and eight calf elk. Pregnant females had significantly (P < 0.001) higher concentrations of all three fecal metabolites than nonpregnant animals, especially later in gestation (March to April). We developed all possible combinations of univariate, bivariate, and multivariate discriminant function analysis models to determine those variables most useful in predicting memberships of pregnant versus nonpregnant elk during the March to April time-period. We validated each model by applying the classification functions to 11 pregnant and eight nonpregnant elk that were not included in the development of the original models. Accuracy of the discriminant function analysis models ranged from 57 to 84%, with the univariate model based on pregnanediol-3-glucuronide concentration providing the highest classification. Fecal metabolite analysis will enable biologists to noninvasively assess the pregnancy status of elk, especially when diagnoses are based upon multiple samples collected between mid-March and mid-April.
Excess dietary glucose may be a factor in several captive wildlife diseases and reproductive abnormalities. The first step in understanding the health consequences of diets high in glucose is to characterize how dietary glucose concentrations change circulating glucose profiles. We adapted the glycemic index approach to detect differences in blood glucose concentrations in white rhinos in response to different meals. Six white rhinos were fasted overnight then randomly assigned to be fed 5 kg of grass hay and one of five meals varying in digestible energy (DE) availability and source (10% DE glucose, 5% DE glucose, 10% DE pelleted horse feed, 10% DE lucerne hay, 10% DE grass hay). After eating, the blood glucose response peaked 45-90 min later and remained elevated up to 180 min. Area under the curve results demonstrated that the blood glucose response was not different between diets. However, at 90 min, serum glucose levels in rhinos eating the 10% lucerne hay diet were significantly lower than the 5% glucose and 10% glucose diets but not the 10% pellet nor 10% grass hay diets. The changes in blood glucose responses to different diets were similar in magnitude to reported domestic horse profiles but are higher than predicted by allometric scaling. We conclude that the grass hay, lucerne hay and low glycemic index horse pellets fed in this study resulted in similar blood glucose responses in white rhinos. The validation of the methodology used in this study is a first step towards elucidating the relationship between glucose, obesity, health and reproduction in rhinos.
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