Birds from the temperate and cold zones show annual sexual activity accompanied by gonadal changes and fluctuation in their brain gonadotropin-releasing hormone (GnRH) levels. However, most of the studies were done on captive birds where the constant environment can profoundly modify periodical changes. Therefore our aim was to reveal annual variations of hypothalamic and gonadal changes in male, free-living European starlings
captured directly from their natural environment. We analyzed hypothalamic GnRH-I immunoreactivity and testes volume. Four key time points of the active reproductive cycle and the photorefractory phase were studied. GnRH-I immunoreactivity was analyzed in the preoptic area (POA) and the median eminence (ME). Photorefractory birds (August) with regressed gonads had the lowest level of GnRH-I immunoreactivity compared to other birds from the active reproductive phases. These results suggest that parallel with the gonadal volume GnRH-I undergoes seasonal changes in adult male free-living European starlings.
The non-invasive faecal sampling and RIA was used to measure faecal equivalents of testosterone (T), dehydroepiandrosterone (DHEA), oestradiol-17β (E2) and progesterone (P4) in juvenile and adult great bustard males. Possible connections of diurnal and seasonal changes of sexual steroid levels and display activity were studied. Correlations were found between sexual steroid equivalent levels of faeces and display activity and agonistic behaviour in the different phases of annual cycle of adult males. In early display period increasing levels of androgens were measured, during main display period very high androgen dominance was observable against E2 and P4. During postnuptial moult strong T decrease and DHEA and P4 increase were detected. Elevation of E2 was measured during wintering. In juveniles level of DHEA was higher than level of T suggesting its importance in immature males. Decrease of T was detected between reproductive period and postnuptial moult and DHEA between reproduction and wintering, accompanying with E2 elevation. The inhibiting effect of inclement weather on gonad functions also was detected in our study. We suppose that the unexpected cold weather with strong wind depressed the levels of androgens both in juveniles and adults and the increase of faecal E2 was also detected.
Authors:P. Péczely, F. Bogenfürst, Margit Kulcsár, and Bea Polgár
Plasma levels of testosterone (T), 17-β-estradiol (E2), progesterone (P4), dehydroepiandrosterone (DHEA), corticosterone (B), thyroxine (T4) and triiodothyronine (T3) were monitored during postnuptial and the prenuptial molt in domestic goose (Anser anser domesticus) in both sexes. 1. At the beginning of postnuptial molt (when the old, worn dawny-, and cover feathers’ loss starts) in ganders, the levels of T, E2, P4 decrease while DHEA and B significantly increase. The elevated levels of T4 and low T3 concentrations characteristic of the last phase of the reproduction, remain unchanged. In layers, similar changes were observed, however, B decreases. 2. In the early phase of outgrowth of wing and cover feathers, plasma levels of T, E2 and P4 are low. Elevated B, DHEA and T4 concentrations decrease in ganders, while in layers DHEA increases and B and T4 levels remain unchanged. T3 increases in both sexes. 3. The subsequent intensive outgrowth period of wing- and cover feathers both in ganders and in layers is characterized by very low levels of T, E2, DHEA and T4, but P4 increased, and T3 concentration remain high. 4. At the end of postnuptial molt — when the outgrowth of dawny, cover-, and wing feathers stops — very low T, E2, P4, DHEA and T4 levels and and high T3 plasma levels were found in both sexes. Fast increase of plasma B was detected in ganders, while in geese, B concentration remain high. 5. During prenuptial molting (outgrowth of contour and tail feathers) low E2, P4 and T4, increasing T and DHEA, but very high T3 and B plasma concentration were measured in ganders. In layers, very low T, E2, P4, DHEA and T4 levels, and very high B and T3 levels were found. 6. At the beginning of the fall-winter sexual repose (postmolting stage) T, E2, P4, DHEA and T4 levels increase, T3 and B declines in both sexes. 7. In the subsequent phase of fall-winter period (preparatory stage) there is a further increase in T, P4 and T4, a fast increase of B and a decrease of E2, DHEA and T3 in ganders. In layers, T, P4 and DHEA decrease, B increases and the T4 and T3 do not change. 8. At the beginning of reproduction high T level, unchanged DHEA, slightly declined P4, and decreased E2, T4, T3 and a strong decline of B concentrations occur in ganders. In layers, T is further increased, E2 and P4 shows high levels, and, at the same time DHEA and T3 remain unchanged, while B and T4 decrease.
Authors:K. Kelemen, P. Péczely, Zs. Szőke, and V. Ladjánszky
In a comparative study, a relatively simple and high sensitivity method was developed for analysis of testosterone-equivalent(s) in the faeces of different bird species. To determine the recovery of extractions and purifications, tritium-labelled testosterone was added to the wet samples. Then the samples were treated with sodium dodecil sulphate (SDS), an emulsificator to “open-up” the complex, lipid-coated particles of faecal samples. This emulsification resulted in the decrease of the quantity of interfering substances after diethyl-ether extraction and the linearity of the measured testosterone equivalents from aliquots in the range of 2 and 10 mg of faeces. In the RIA, we applied a group specific polyclonal testosterone antibody which cross-reacted with reduced metabolites and at a certain level with sulphate conjugates as well. The use of Helix enzymes did not modified significantly the results of the analysis relating to a low level of conjugated androgens in the faecal extracts. The biological validity of the method was tested on domestic cockerels, where between the plasma and faecal testosterone values a four hours phase shift was observed, with a correlation of 0.6355. This method is suitable for “non invasive”, behavioural-ethological studies.
Authors:Do Thi Dong Xuan, Barbara Végi, Zs. Szőke, and P. Péczely
Changes in plasma DHEA, testosterone (T) and 17-B-oestradiol (E2) levels were examined in domestic geese of both sexes in the fall and winter. The levels of steroid hormones were determined in blood plasma by means of radio-immunoassay (RIA). A so-called second (autumn) cycle was induced in geese via a dark-room preparation and natural keeping conditions. The plasma levels of DHEA showed a minor peak at onset of the autumn breeding and a major one prior to the more intense spring reproduction in both sexes. The seasonal curves of plasma DHEA appeared fairly similar in ganders and layers and without considerable differences between the absolute values. In ganders, plasma DHEA peaks preceded the elevations in T levels in the fall and spring alike. With layers, in turn, the autumn and spring peaks of plasma DHEA appeared after the peaks in E2 levels. With ganders, the concentration of plasma T seemed to predominate between the two androgens throughout the experimental period. With layers, in turn, the concentration of DHEA surpassed the level of plasma E2 at the time of the peak periods and other times during the study, as well. In domestic geese, DHEA is probably involved in the autumn physiological processes and the induction of reproduction during fall and early spring periods, alike.
Authors:Zsuzsa Szőke, Éva Váradi, K. Kelemen, A. Biczó, and P. Péczely
Intestinal passage time of coloured fodder and testosterone turnover were examined by faecal steroid analysis in mallards in the reproductive and postrefractory period. In the latter, the discharge of coloured fodder began 36 minutes after ingestion in males, and 56 minutes in females. During reproduction the discharge began 93 minutes and 112 minutes after ingestion in males and females, respectively. Total passage time was similar in the reproductive and postrefractory period in both sexes. After intraperitoneal testosterone injection, faecal samples were collected for 8 hours and testosterone levels were measured using RIA. In the postrefractory period, 1-2 hours after testosterone loading a strong increase of faecal testosterone content developed in males, meanwhile a slighter testosterone peak appeared in females. During reproduction testosterone excretion began 1.5-2 hours after injection in both sexes but in females its increase was smaller. The duration of response to testosterone loading was 5 hours in both periods and both sexes. Intensive excretion after T loading appeared earlier in males than in females, but total passage time finished at the same time: 5 hours after loading. The character of testosterone excretion was corresponding to the passage of fodder-chimus-faeces in the reproductive and postrefractory period in both sexes.