- 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. 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 .
Using fecal RIA, Messiers et al. (1990) were able to reliably detect pregnancy after day
50 of pregnancy in free-roaming caribou . 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 . 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 . 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