Non‐invasive monitoring of avian reproduction by simplified faecal steroid analysis

Abstract

The measurement of urinary steroid metabolites has proved a reliable method for monitoring reproductive changes in a variety of mammalian species. Development of related techniques for assessing avian reproductive function has shown that sexing of various species is feasible and that the following of individual reproductive changes may be possible. This paper reports on the use of a simplified procedure for assay of specific excreted steroids in a 1: 60 dilution of a 0.4 g dried faecal sample from male and female Japanese quail, and the monitoring of steroid hormone changes in the plasma and faeces throughout a photoperiodically induced reproductive cycle. Immunoreactive steroid measurements were made directly by radioimmunoassay (RIA) of ahquots of faecal homogenates in phosphate buffer and did not involve hydrolysis of steroid conjugates or organic solvent extraction. Measurements were made of immunoreactive testosterone, oestradiol‐3‐glucuronide (E‐3‐gl) and pregnanediol‐3α‐glucuronide (Pd‐3α‐gl). Plasma testosterone and progesterone concentrations, in males and females, were compared to faecal immunoreactive testosterone and Pd‐3α‐gl, respectively. Exposure to stimulatory long daylengths of 20L:4D (LD) resulted in a rise of both plasma and faecal testosterone followed by a reduction after subsequent transfer back to short daylengths of 8L:16D (SD). Male faecal immunoreactive testosterone levels were significantly correlated with the plasma testosterone concentrations (0.59, P<0.001, n= 70) and with the phase of the reproductive cycle. Faecal immunoreactive Pd‐3α‐gl levels increased following exposure to LD, and female values were well correlated with plasma progesterone concentrations (0.79, P <0,001, n= 56) and with the pattern of egg laying. Faecal immunoreactive E‐3‐gl levels were higher in LD than SD birds with higher levels in females compared to males, even under SD photoperiods. For long‐term monitoring of the reproductive status of Japanese quail, faecal immunoreactive testosterone and Pd‐3α‐gl measurements, in a 1:60 dilution of a random 0.4 g dried faecal sample, were found to be as reliable and informative as plasma testosterone and progesterone measurements, respectively.

Excretion and metabolic fate of radiolabeled estradiol and testosterone in the cockatiel (Nymphicus hollandicus)

“…Estrogen profiles have been documented to reflect ovarian activity accurately [Cockrem and Rounce, 1994], and a pre-ovulatory androgen rise Farner, 1978, 1980;Kofuji et al, 1993;Lee et al, 1995] confirms the previously described fact that testosterone is a precursor of estradiol [Tanabe et al, 1981]. In earlier studies, testosterone immunoreactivity has been the predominant end point for androgen measurements in feces from avian species [Czekala and Lasley, 1977;Bercovitz et al, 1978;Lee et al, 1995]; however, other work has demonstrated that free steroids may be only a small component of the excreta, and conjugated polar androgen metabolites dominate [Bishop and Hall, 1991].…”

“…These fecal/urine samples can be collected from the ground, alleviating the need to disturb the animal. Steroids excreted in fecal/urine samples from birds have been documented to reflect circulating hormone levels [Kubodera et al, 1988;Bishop and Hall, 1991;Cockrem and Rounce, 1994] and have been utilized to monitor both captive [Bercovitz et al, 1982;Ishii et al, 1994] and wild [Kofuji et al, 1993;Cockrem and Rounce, 1995;Kikuchi et al, 1996] populations of birds. Fecal/urine samples are often extracted with organic solvents and assayed utilizing radioimmunoassays.…”

“…However, these methods are labor intensive and laboratory bound. Recent studies have attempted to alleviate these problems by employing aqueous buffer solubilization [Bishop and Hall, 1991;Lee et al, 1995] and enzyme immunoassays [Lee et al, 1995] for measuring fecal hormones. These methods offer a faster, simpler, and more economical technique for obtaining hormone levels than were available previously.…”

Photoperiod Conditions Influence Fecal Estradiol Levels in Females of Migratory Reed Bunting Emberiza schoeniclus and Non-migratory Meadow Bunting Emberiza cioides.

“…2). Previous studies using Japanese Quails have demonstrated that measurement of sex steroid hormones excreted into feces enables estimation of the plasma levels of these hormones (Bishop & Hall 1991). In female Reed Buntings that were maintained under increasing daylength from LD 10: 14 to LD 13: 11, the levels of estradiol in both plasma and feces increased significantly (Nakamura & Shimada 1988; Fig.…”

“…However, little blood can be extracted from small birds, and such sampling causes great stress. Therefore, a method for measuring the levels of sex steroid hormones, such as estradiol, progesterone and androgen, in bird feces has been developed (Bishop & Hall 1991). Since changes in fecal sex steroid levels in the Japanese Quail Coturnix coturnix japonica show a significant positive correlation with those in plasma (Bishop & Hall 1991), the measurement of sex steroids excreted into feces makes it possible to estimate the plasma levels of these hormones in a stress-free manner.…”