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.