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Graham, L. H., Goodrowe, K. L., Raeside, J. I., & Liptrap, R. M. (1995). Non-invasive monitoring of ovarian function in several felid species by measurement of fecal estradiol-17-beta and progestins. Zoo Biology, 14(3), 223–237.
Abstract: An extraction and assay procedure to measure fecal estradiol-17-beta and progestin concentrations in several cat species was developed and validated for use for noninvasive monitoring of ovarian function. Fecal samples were collected over a range of 3-20 months from female tigers (three), lions (three), snow leopards (three), cheetahs (two), caracals (two), and domestic cats (five). Samples were extracted with 90% methanol, lipids removed with petroleum ether, and the estradiol and progestins in the methanol measured by radioimmunoassay (RIA). High Performance Liquid Chromatography (HPLC) fractionation and subsequent RIA of the fractions indicated that the estradiol-17-beta antiserum cross-reacted primarily with estradiol-17-beta in the feces of lions and tigers and was assumed to be specific for estradiol-17-beta in the feces of other species as well. However, there were several immunoreactive compounds, presumably progesterone metabolites, excreted in the feces which varied both quantitatively and qualitatively among species. The behavior of tigers, lions, cheetahs, and caracals was visually monitored during the collection period and frequency of sexual behaviors was positively correlated with increases in fecal estradiol in all species observed. The mean fecal estradiol-17-beta peaks were as follows: tigers, 128.0 +- 13.1; lions, 186.0 +- 14.8; snow leopards, 136.7 +- 15.9; cheetahs, 140.9 +- 9.0; caracals, 24.5 +- 4.0; and domestic cats 158.9 +- 19.3 ng/gm. Fecal progestin concentrations rose significantly (P lt 0,001) only after breeding or during pregnancy and were as follows: tigers, 5.6 +- 0.6; lions, 1.9 +- 0.1; cheetahs, 8.4 +- 1.1; and caracals, 2.4 +- 0.4 mu-g/gm. Fecal progestins were elevated for one-half to two-thirds of the gestation length during presumed pseudopregnancy but remained elevated throughout successful pregnancies. These results suggest that ovarian function can be monitored noninvasively in the family Felidae by the measurement of fecal estradiol-17-beta and progestin concentrations.
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Kazensky, C. A., Munson, L., & Seal, U. S. (1998). The effects of melengestrol acetate on the ovaries of captive wild felids. Journal-of-Zoo-and-Wildlife-Medicine, 29(1), 1–5.
Abstract: Melengestrol acetate (MGA) is the most widely used contraceptive in zoo felids, but the mechanism of contraception and the pathologic effects have not been investigated. For this study, the effects of MGA on folliculogenesis were assessed, and the association of MGA with ovarian lesions was evaluated. Comparisons were made among the histopathologic findings in the ovaries from 88 captive wild felids (representing 15 species) divided into three groups: 37 currently contracepted with MGA, eight previously exposed to MGA, and 43 never contracepted. Ninety-one percent of the felids evaluated had tertiary follicles, and no differences were noted between contracepted and uncontracepted cats. Some MGA-contracepted cats also had corpora lutea indicating recent ovulation. These results indicate that folliculogenesis is not suppressed by current doses of MGA and ovulation occurred in some cats. Therefore, the contraceptive actions of MGA do not occur by suppressing folliculogenesis, and MGA-contracepted felids likely have endogenous estrogens that may confound progestin effects on the uterus. Cystic rete ovarii was the most common pathologic finding, but they were not more prevalent in MGA-contracepted cats. These findings indicate that MGA is not associated with ovarian disease, including ovarian cancer, in contrast to the uterine lesions noted in MGA-treated cats.
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