Role of gonadal and adrenal steroids and thyroid hormones in the regulation of molting in domestic goose

Crosstalk between prolactin, insulin-like growth factors, and thyroid hormones in feather growth regulation in neonatal chick wings

The elongation of primary feathers in neonatal chicks is delayed by the late-feathering K gene located on the Z chromosome. We recently found that the K gene slows feather growth by reducing the number of functional prolactin (PRL) receptor (PRLR) dimers. In this study, we investigated the molecular mechanisms by which PRL promotes feather elongation. RT-qPCR and immunohistochemistry analyses revealed that PRLRs are predominantly localized in the pulp rather than in the epidermal layer of the feather follicle. Treatment of primary cultured feather pulp cells with PRL increased the expression of mRNAs for insulin-like growth factors (IGFs; IGF-1 and IGF-2) and type 2 deiodinase (DIO2). Furthermore, treatments with IGF-1 and triiodothyronine (T3) reciprocally enhanced the expression of mRNAs for DIO2 and IGFs. Additionally, BrdU staining in neonatal chicks showed that T3 promoted cell proliferation in both the epidermal layer and pulp cells, while this effect was suppressed by an IGF-1 receptor (IGF1R) inhibitor. These findings suggest a novel model in which PRL upregulates IGFs and DIO2 in feather pulp cells, creating a positive feedback loop between IGFs and T3, ultimately leading to the promotion of cell proliferation in both the epidermal layer and the pulp cells by IGFs. This is the first report proposing crosstalk between PRL, thyroid hormone (TH), and IGFs in feather follicles.

Alterations in gonadotropin, prolactin, androgen and estrogen receptor and steroidogenesis-associated gene expression in gander testes in relation to the annual period

Physiological mechanisms of seasonal changes in testicular function in birds are not fully elucidated. The balance between androgens and estrogens and testis sensitivity for gonadotropin and gonadal steroids are still unclear. The aim of the study was to examine: (1) the changes in circulating and intra-testicular steroid hormone levels and their relationship; (2) the mRNA expression of testicular gonadotropin, prolactin (PRL), progesterone (P4), androgen, and estrogen receptors, and (3) key steroidogenesis processes-related genes with immunofluorescent localization of aromatase in gander testes during the annual period. Testes from ganders (n = 25) in the first reproduction season were obtained at five breeding stages, i.e., prebreeding (PrB), peak of reproduction (PR), postbreeding (PoB), nonbreeding (NB), and onset of reproduction (OR). Males were kept under breeding conditions. It was found that plasma P4 levels decreased at the PoB and NB stages, whereas intra-testicular P4 was the highest in the NB stage. Intra-testicular estradiol (E2) levels were higher at the PoB and NB stages than the other stages, whereas testosterone (T) levels showed a nearly opposite pattern. The plasma estradiol-to-testosterone ratios were higher at the PrB, PoB and NB stages compared to other stages. The transcript abundances for luteinizing hormone receptor (LHR), PRL receptor (PRLR), estrogen receptor alpha (ERα), and estrogen receptor beta (ERβ) also change in testicular tissue during the annual period. Moreover, StAR mRNA expression was upregulated at the PoB and NB stages, and CYP11A1 transcript level was the highest at the PoB stage. Stage-dependent changes in the CYP19A1 mRNA and aromatase protein levels with higher abundances of transcript at PoB and NB stages and protein at the NB stage were observed. Localization and immunofluorescent signal intensity for aromatase also differed in relation to the examined stages. It may be suggested that differential E2 levels, as well as aromatase expression and localization across annual stages are responsible for the seasonal activation/inactivation stages of testis spermatogenesis in domestic ganders. These data strongly suggest a role of aromatase in the control of gander steroidogenesis as changes in this enzyme level are associated with alternation in gonadal steroid hormones. In addition, joint action with others hormones, like PRL and LH, seems to be important in the final effect of seasonal reproduction potential.

Determination of Annual Plasma Hormone Levels Associated with Reproduction in Long-Day Breeding Domestic Geese

Simple Summary

In domestic birds, breeding practices and optimisation of the microenviroment and nutrition ensure egg production throughout the entire year. However, domestic geese experience an annual cycle of reproductive quiescence and recrudescence. Thus, patterns of reproductive hormones related to the initiation and termination of the breeding–laying period between the sexes seems to be especially important. This paper presents annual patterns of prolactin (PRL), triiodothyronine (T3), thyroxine (T4), testosterone (T), progesterone (P4), and estradiol (E2) in ganders and female geese. Long-day breeding Zatorska geese kept in controlled commercial conditions experienced periods with elevated plasma PRL levels in both sexes post-breeding and during the second half of the breeding–laying period. Increased plasma PRL levels by the end of the breeding–laying period were detected earlier in ganders than in female geese. Annual patterns of thyroid hormones (THs) were partially in agreement with existing theories on the specific role of THs in termination of breeding, which is permissive rather than causal. It may be suggested that ganders terminate their breeding–laying period one month earlier than female geese. These results may be useful in the manipulation of the endocrine axis to extend the duration of seasonal hatching egg production.

Abstract

This paper examines the dynamics of circulating hormone changes connected with reproduction in geese during the annual period related to gonad morphometry. One hundred geese were examined. The levels of prolactin (PRL), triiodothyronine (T3), thyroxine (T4), testosterone (T), progesterone (P4) and estradiol (E2) were estimated. In both sexes, PRL level patterns fit a quadratic trend with elevations in the post-breeding and the second half of the breeding–laying periods. During these periods, differences in the PRL level between sexes were noted. In ganders, increased PRL levels during the laying period occurred earlier compared to in female geese. Cubic trends for T and E2 in ganders and quadratic for T, P4, and E2 in female geese were observed. PRL was negatively correlated with T in both sexes and with P4 and E2 in female geese. A higher level of T3 and variation in T4 in ganders with a quartic trend in ganders vs. a quadratic in female geese were noted. Patterns of PRL, T, and E2 suggested that the breeding–laying period in ganders may be shorter than in female geese. These findings will be used to explore experimental manipulations of the endocrine axis to increase synchronisation of both sexes.

Development, regeneration, and evolution of feathers

The feather is a complex ectodermal organ with hierarchical branching patterns. It provides functions in endothermy, communication, and flight. Studies of feather growth, cycling, and health are of fundamental importance to avian biology and poultry science. In addition, feathers are an excellent model for morphogenesis studies because of their accessibility, and their distinct patterns can be used to assay the roles of specific molecular pathways. Here we review the progress in aspects of development, regeneration, and evolution during the past three decades. We cover the development of feather buds in chicken embryos, regenerative cycling of feather follicle stem cells, formation of barb branching patterns, emergence of intrafeather pigmentation patterns, interplay of hormones and feather growth, and the genetic identification of several feather variants. The discovery of feathered dinosaurs redefines the relationship between feathers and birds. Inspiration from biomaterials and flight research further fuels biomimetic potential of feathers as a multidisciplinary research focal point.

Mating activity of domestic geese ganders (Anser anser f. domesticus) during breeding period in relation to age, testosterone and thyroid hormones

In breeding geese, natural mating applies. The objective of this study was to determine seasonal- and age-related changes in the sexual activity of ganders. Moreover, T, T4 and T3 plasma levels were evaluated. The study was conducted on 2/3-year-old males (n=15) and 1- or 2/3-year-old females (1♂:4♀). Sexual activity of ganders was characterized through the frequency of: courtship, attempts at and successful copulations and total mating activity (MA). Reproductive results manifested by egg production and fertility were recorded. Laying percentage (January-June) was 37.1 and 28.6% for 1-, and 2/3-year-old geese, respectively. MA was noted before the sexual maturity of females and the T level peak. MA was highest at the onset and during peak production (March) for ganders kept with 1-, and 2/3-year-old geese, respectively. From April to May a decrease in fertility with a reduction of the frequency of copulations was observed. At this time low levels of T were noted. The effect of goose age on the MA was shown, with higher frequency of copulations for ganders kept with 1-year-old geese. We suggest that in the successful seasonal mating in geese, social factors such as the presence of females and female age play an important role. The reduction in fertility during the spring period may be associated with decreases in the efficiency of successive mating sequences. The higher frequency of copulations without affecting fertility, for ganders kept with young geese, may be because of differences in sperm transfer or storage/transport efficiency.

Molt–breeding overlap alters molt dynamics and behavior in zebra finches, Taeniopygia guttata castanotis

Costly events in the life history cycle of organisms such as reproduction, migration and pelage/plumage replacement are typically separated in time to maximize their outcome. Such temporal separation is thought to be necessitated by energetical trade-offs, and mediated through physiological processes. However, certain species, such as tropical birds, are able to overlap two costly life history stages: reproduction and feather replacement. It has remained unclear how both events progress when they co-occur over extended periods of time. Here we determined the consequences and potential costs of such overlap by comparing molt and behavioral patterns in both sexes of captive zebra finches (Taeniopygia guttata castanotis) that were solely molting or were overlapping breeding and molt. Individuals overlapping the early stages of breeding with molt showed a roughly 40% decrease in the growth rate of individual feathers compared with birds that were molting but not breeding. Further, individuals that overlapped breeding and molt tended to molt fewer feathers simultaneously and exhibited longer intervals between shedding consecutive feathers on the tail or the same wing as well as delays in shedding corresponding flight feathers on opposite sides. Overlapping individuals also altered their time budgets: they devoted more than twice the time to feeding while halving the time spent for feather care in comparison to molt-only individuals. These data provide experimental support for the previously untested hypothesis that when molt and reproduction overlap in time, feather replacement will occur at a slower and less intense rate. There were no sex differences in any of the variables assessed, except for a tendency in females to decline body condition more strongly over time during the overlap than males. Our data indicate the existence of major consequences of overlapping breeding and molt, manifested in changes in both molt dynamics and time budgets of both sexes. It is likely that under harsher conditions in natural environments such consequences will be more severe and may result in fitness consequences.