Undergraduate Thesis Or Project
 

Progestin analysis by gas chromatography/mass spectrometry in plasma and feces of horses, cattle, and sheep

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  • Much interest has recently been shown in using fecal samples to monitor hormone concentrations in free-roaming animal populations. This process is noninvasive and, therefore, provides easy sample collection and assures no stress-related, physiological responses that might alter the hormonal data. Concerns have been expressed, however, that the hormone concentrations detected in fecal samples may not correlate with those detected in blood plasma[1]. Since the bulk of our steroid hormone data has been generated from plasma, this is a legitimate concern when comparing with fecally derived data. There have been few blood and fecal comparison studies but, Larter et al. (1994) reported from radioimmunoassays (RIA) that progestin concentrations in cattle were similar whether obtained from plasma or fecal samples. Kirkpatrick et al. (1993) have established methods of detecting pregnancy with fecal RIA and ovulation with fecal enzyme immunoassay (EIA) in Yellowstone bison [2]. Using fecal RIA, Messiers et al. (1990) were able to reliably detect pregnancy after day 50 of pregnancy in free-roaming caribou [3]. These reports indicate that if the hormones and their concentrations are not similar, they are at least useful in similar ways as plasma data is. It is only a matter of time until enough fecal data has been published for there to be an accepted "norm" of hormone profiles in various species. The impetus for this study is the cross-reactivity of RIA and EIA. Holtan et al. (1991) reported that even with rigorous sample purification, cross-reactivity is inevitable when these techniques are used and can significantly alter the data [4]. Others, including Houghton et al. (1991) and Larter et al. (1994), have expressed the same concerns [5, 1 ]. The assays, however, are easy to use, inexpensive, and, given the radical hormone concentration changes throughout pregnancy, they provide enough data to monitor reproductive status in wild populations. As an alternative to immunoassay, GC/MS has been used to analyze blood plasma to identify and quantify hormones. Methods have been established that provide highly specific hormonal data (ie. elucidation of isomers) and are also sensitive, accurate, and precise [4]. This study was designed to establish GC/MS methods for analyzing fecal progestins in horses, sheep, and cattle with GC/MS plasma progestins serving as a basis for comparison. In addition, sheep plasma was analyzed for progesterone (P4) by RIA and GC/MS to compare results between these methods in plasma.
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