Gonadotropin releasing hormones and their receptors in avian species

n all vertebrates, gonadotropin releasing hormone (GnRH) is a key component of the hypothalamo-pituitary-gonadal axis. In birds, two distinct forms of GnRH (cGnRH-I and cGnRH-II) have been characterized, and a third immunoreactive form similar to lamprey GnRH-III has been reported. Each GnRH is produced by a different population of neurons. cGnRH-I is predominantly synthesized in cells located in the preoptic and septal areas, whereas cGnRH-II and -III are produced in neurons located mainly in the mesencephalon and around the third ventricle, respectively. Although GnRH neurons have been shown to project fibers to the median eminence, it is still unclear whether all three peptides are released in the hypothalamo-pituitary portal vascular system. Nonetheless, in vitro as well as in vivo experiments confirmed that they all have the ability to induce the release of gonadotropins. In the anterior pituitary gland, GnRHs mediate their effects by binding to specific G-coupled protein receptors, and in chickens, two different receptors have been characterized (cGnRHR-I and cGnRHR-II). In addition to the full-length receptors, several splice variants have also been detected. Although the physiological relevance of these variants is not known, they may participate in the regulation of intracellular signaling. While the expression of the full-length cGnRHR-I appears to fluctuate during an ovulatory cycle, levels remain constant between reproductive stages in chickens. In contrast, pituitary levels of cGnRHR-II mRNA are directly correlated with the reproductive status of the bird. Whether these two GnRHRs are expressed by the same cells in the anterior pituitary gland is not known. However, since luteinizing hormone (LH) and follicle stimulating hormone (FSH) are produced by two different cell populations in chickens, it is possible that different combinations of GnRHs and GnRHRs differentially mediate the synthesis and release of these gonadotropins

Variations des capacités reproductrices de l'escargot « Petit-gris », Helix aspersa Müller (Mollusque Gastéropode Pulmoné Stylommatophore), selon son origine géographique. II. Incubation des oeufs et éclosion des jeunes

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Effects of environmental and social factors on incubation behavior, endocrinological parameters, and production traits in turkey hens (Meleagris gallopavo)

WOS:A1997XR96600019International audienceHens raised in three different environments were assessed for changes in egg production performance, the rate of incubation behavior expression, and plasma levels of luteinizing hormone (LH) and prolactin for 20 wk following the laying of the first egg. The environments were individual (IFP) or collective floor pens (CFP) and individual battery cages (Cp and Cnp). The hens from three experimental groups (IFP, CFP, and Cp) were transferred from a short (6 h) to a long (14 h) photoperiod, whereas the ones from the remnant (Cnp) were left under a short one. Increase of the photoperiod induced significant increases (P \textless 0.05) in levels of prolactin and LH after I d, and resulted in the onset of egg laying in a delay of 14 d in all groups. However, the overall egg laying performance was highest for the IFP hens. The CFP and IFP hens laid 98 and 24% of their eggs inside the nest boxes, respectively. The hens raised in battery cages did not express incubation behavior, whereas 50 and 33%, respectively, of the CFP and IFP hens did. During the Ist wk of egg laying, levels of prolactin increased for all photostimulated hens but to a greater extent for CFP hens. Higher increases in levels of prolactin were associated with the expression of incubation behavior; however, prolactin levels of nonincubating laying hens were also higher under the CFP treatment. It appears that the rate of expression of incubation behavior, as well as changes in the plasma levels of prolactin and LH throughout an egg production period, are dependent upon rearing conditions in turkey hens

Respective Effects of Chicks and Nest on Behavior and Hormonal Concentrations of Incubating Domestic Hens

WOS:A1993LG72300021International audienceRemoval of incubating hens from their nestboxes or substitution of chicks for eggs disrupt incubation; prolactin levels decrease whereas luteinizing hormone and gonadal steroid concentrations tend to rise. The present experiment was undertaken to determine the relative influence of removing the nest (nest-deprived hens), adding chicks (maternal hens), or both (maternal nest-deprived hens), on the behavior and hormone concentrations of incubating hens. The results confirm that nest removal, as well as adding chicks, stops incubation. No differences were found between maternal and maternal nest-deprived hens' behavioral responses or hormonal concentrations. These results do not support the hypothesis that the drop of plasma prolactin observed in maternal hens is the consequence of the nest abandonment. In contrast, nest-deprived hens presented lower concentrations of prolactin and higher concentrations of estradiol than maternal and maternal nest-deprived hens. Moreover, the nest-deprived hens presented lower concentrations of prolactin and higher concentrations of LH and estradiol than the hens given chicks. We assume that physical contact with chicks, during brooding bouts, slows down the decrease of prolactin secretion and inhibits LH and estradiol release at the end of incubation

Influence of the presence of chicks on the ability to resume incubation behavior in domestic hens (Gallus domesticus)

WOS:A1995TK54200001International audienceIn this study, hormonal and behavioral changes associated with nest deprivation in the absence or in the presence of chicks (replaced every day or not) were investigated in incubating hens. Prolactin levels decreased, whereas LH and E2 levels increased following nest deprivation. Surprisingly, the presence of chicks had no effect on prolactin changes. However, the presence of chicks significantly limited increases in plasma LH and estradiol. Furthermore, this inhibitory effect was greater when day-old chicks were replaced every day. On the other hand, the presence of chicks induced the emergence of specific maternal behavior, while, surprisingly, one-third of the nest-deprived hens without chicks continued to incubate, After a 3-day deprivation period, readiness to renest was maintained for a percentage of hens. Thus more than 2/3 of hens deprived of the nest for 3 days in the presence of chicks returned to their nests during the first day of being allowed to do so, versus less than 1/3 of hens without chicks among those that previously disrupted incubation behavior. Plasma prolactin concentrations of these renesting hens increased rapidly and reached again levels characteristic of incubating hens. We conclude that, under our experimental conditions, presence of chicks maintains readiness to incubate without maintaining high levels of plasma prolactin. (C) 1995 Academic Press, Inc

Genetic parameters of caviar yield, color, size and firmness using parentage assignment in an octoploid fish species, the Siberian sturgeon Acipenser baerii

International audienceAquaculture is presently the only sustainable way of enhancing sturgeon caviar production as the use of wild stocks is banned throughout the world. Hence sustainable management and efficient genetic improvement of domesticated populations are major challenges for the development of farmed caviar. We estimated genetic parameters of caviar yields and quality traits (size, color and firmness) in the polyploid Siberian sturgeon A. baerii, one of the major sturgeon species farmed for meat and caviar worldwide. This study was performed in commercial breeding conditions, where two factorial mating plans were created to produce 77 families. Larvae were pooled at hatching and reared in common environment until the age of caviar production. We phenotyped 494 females, which were successfully assigned to their parents with microsatellite markers using a newly developed software, designed to manage genotypes with varying ploidy levels, up to 8 N. The genetic parameters were estimated using heteroscedastic multi-trait BLUP animal models. Heritability of body weight, ovary weight, caviar weight, caviar (egg) size, caviar yield, caviar firmness and caviar color were moderate to high (0.13 to 0.66) depending on the trait. Moderate negative genetic correlations were estimated between growth and caviar yields (−0.28 to −0.37) while genetic correlations between caviar (egg) size and caviar yield were more negative (−0.70 to −0.76). These results provide favorable grounds to improve the efficiency of farmed caviar production by selective breeding

Influence of stimuli from chicks on behavior and concentrations of plasma prolactin and luteinizing hormone in incubating hens

WOS:000074279800007International audienceRemoval of eggs from the nests of incubating birds or substitution of eggs for chicks disrupts incubation behavior and induces changes in the secretion of prolactin and luteinizing hormone (LH). The aim of the present study was to determine how different stimuli, such as physical contact with eggs and tactile, visual, and/or auditory cues from chicks, interact to control the transition between incubation and brooding and to induce changes in prolactin and LH plasma concentrations. Physical contact with chicks, in the presence or absence of eggs, induced brooding behavior and an immediate fall in plasma prolactin concentration and a gradual increase in LH concentration. Vocalizations, particularly clucking and food calls, increased rapidly while incubation and nest attachment disappeared slowly. No change in plasma prolactin o

Behaviour and hormone concentrations in nest deprived and renesting hens

WOS:000074778000001International audience1. Nest and egg deprivation is a procedure traditionally used to disrupt incubation behaviour expression in commercial flocks. The aim of this study was to establish how nest deprivation affects the subsequent changes in behaviour and hormone secretion and whether readiness to renest is related to hormone concentration before and during nest deprivation. 2. Incubating broiler breeder hens were deprived of their nest either in their familiar environment, by blocking the nest entrance in the home cage or in an unfamiliar environment, by transfer in a different cage. After 3 days of nest deprivation, next access was allowed and readiness to incubate tested. 3. Both methods of nest deprivation resulted in the expression of similar behaviours associated with the disruption of incubation, and similar increases in plasma LH and oestradiol and decreases in plasma prolactin. The percentage (approximate to 70%) of hens which renested after either method of nest deprivation did not differ significantly. 4. Readiness to renest was not related to the concentrations of plasma prolactin measured before or during the 3 days of nest deprivation. However, hens which would later renest could be identified by using behavioural criteria. They emitted more avoidance trills before, and sat on the wire floor for longer periods during, the nest deprivation period than the others

Genetic architecture and genomic selection of female reproduction traits in rainbow trout

International audienceBackground: Rainbow trout is a significant fish farming species under temperate climates. Female reproduction traits play an important role in the economy of breeding companies with the sale of fertilized eggs. The objectives of this study are threefold: to estimate the genetic parameters of female reproduction traits, to determine the genetic architecture of these traits by the identification of quantitative trait loci (QTL), and to assess the expected efficiency of a pedigree-based selection (BLUP) or genomic selection for these traits.Results: A pedigreed population of 1343 trout were genotyped for 57,000 SNP markers and phenotyped for seven traits at 2years of age: spawning date, female body weight before and after spawning, the spawn weight and the egg number of the spawn, the egg average weight and average diameter. Genetic parameters were estimated in multi-trait linear animal models. Heritability estimates were moderate, varying from 0.27 to 0.44. The female body weight was not genetically correlated to any of the reproduction traits. Spawn weight showed strong and favourable genetic correlation with the number of eggs in the spawn and individual egg size traits, but the egg number was uncorrelated to the egg size traits. The genome-wide association studies showed that all traits were very polygenic since less than 10% of the genetic variance was explained by the cumulative effects of the QTLs: for any trait, only 2 to 4 QTLs were detected that explained in-between 1 and 3% of the genetic variance. Genomic selection based on a reference population of only one thousand individuals related to candidates would improve the efficiency of BLUP selection from 16 to 37% depending on traits.Conclusions: Our genetic parameter estimates made unlikely the hypothesis that selection for growth could induce any indirect improvement for female reproduction traits. It is thus important to consider direct selection for spawn weight for improving egg production traits in rainbow trout breeding programs. Due to the low proportion of genetic variance explained by the few QTLs detected for each reproduction traits, marker assisted selection cannot be effective. However genomic selection would allow significant gains of accuracy compared to pedigree-based selection