Endocrine and molecular regulation mechanisms of the reproductive system of Hungarian White geese investigated under two artificial photoperiodic programs

Effect of active immunization with OPN5 on follicular development and egg production in quail under different photoperiods

OPN5 is one of the main deep brain photoreceptors (DBPs), converting photoperiodic information into neuroendocrine signals to regulate reproduction in birds. This study investigated the mechanism of OPN5-mediated photoperiodic regulation of reproduction by active immunization against OPN5. 96 female quail were divided into OPN5-immunized and control group under the same photoperiod: 16 L:8 D (d 1 to d 35), 8 L:16 D (d 36 to d 70) and 12 L:12 D (d 71 to d 126). OPN5-immunized group was conducted with OPN5 protein vaccination and control group was given a blank vaccine. Samples were collected on d 1, d 30, d 60, and d 126. Results showed switching photoperiod to 8 L:16 D decreased the laying rate, GSI%, numbers of YFs and WFs, serum levels of PRL, P4 and E2, and pituitary PRL and TSHβ protein expressions in both groups (P < 0.05). Whereas the OPN5-immunized group exhibited higher laying rates than the control group (P < 0.05). The control group showed reduced GnRHR and TSHβ gene expressions in the pituitary and increased GnIH and DIO3 transcript and/or protein abundance in the hypothalamus. (P < 0.05). The OPN5-immunized group had lower DIO3 expression at both mRNA and protein levels. (P < 0.05). Switching photoperiod from 8 L:16 D to 12 L:12 D increased the laying rates, GSI%, numbers of YFs and WFs, serum levels of PRL, and PRL protein expression in both groups (P < 0.05), and the responses were more pronounced in OPN5-immunized group (P < 0.05). In contrast to the control group, quail with OPN5-immunization had higher OPN5 and DIO2 transcript and/or protein levels but lower DIO3 expressions in the hypothalamus along the transition photoperiods (P < 0.05). The results revealed that OPN5 responds to photoperiod transition, and its activation mediates related signaling to up-regulate TSH-DIO2/DIO3 pathway and VIP-PRL secretion to prime quail reproductive functions.

Research Note: Effect of different photoperiodic programs from rearing period on the reproductive performance and hormone secretion of White King pigeons

The photoperiod is an important factor during rearing and laying period that affects age and body weight at sexual maturation and reproductive performance in poultry; however relevant research on this factor in pigeons is still lacking. Thus, this study investigated the effects of different photoperiodic programs on the reproductive performance and hormonal profile in White King pigeons. From 101 d of age, the pigeons in the control group were exposed to a natural photoperiod until 160 d, and then to a photoperiod of 16 h (16 light [L]: 8 dark [D]) and lasted for 200 d. Pigeons in the 3 experimental groups were exposed to a short photoperiod of 8L: 16D until 160 d, and then to 14L: 10D, 16L: 8D, and 18L: 6D, respectively. The results showed that light-restriction (8L: 16D) during the rearing period and then 14L: 10D or 16L: 8D photostimulation delayed the age at first egg laying in pigeons. However, 16L: 8D after an 8L: 16D photoperiod during the breeding period ensured maximum photosensitivity, and significantly improved the reproductive performance (egg production and fertility rates) in pigeons. Moreover, the highest reproductive performance in group under16L: 8D after 8L: 16D photoperiodic program was accompanied by improved follicle-stimulating hormone and estradiol levels and reduced prolactin hormone levels. The results indicated that photoperiodic programs from rearing to laying period are closely related to the reproductive performance of White King pigeons. The results provide information that 8L: 16D during rearing period and 16L: 8D during laying period can be used to enhance reproductive performance in the pigeon industry.

Effect of immunization against OPN5 on the reproductive performance in Shan Partridge ducks under different photoperiods

Photoperiod is an important environmental factor that influences seasonal reproduction behavior in birds. Birds translate photoperiodic information into neuroendocrine signals through deep brain photoreceptors (DBPs). OPN5 has been considered candidate DBPs involved in regulating seasonal reproduction in birds. We found that OPN5 could mediate light to regulate the follicle development in ducks. In this study, we further verified the effect of OPN5 on follicular development in Shan Partridge ducks by immunizing against the extracellular domain (ECD) of OPN5. We investigated the specific regulatory mechanism of photoperiod mediated by OPN5 on the reproductive activity of ducks. The trial randomly divided 120 Shan Partridge ducks into 3 groups with different treatments: the immunization of OPN5 group was done at d0, d15, d30, and d40 with 1 mL of vaccine containing OPN5 protein (thus containing 1, 1, 0.5, and 0.5 mg of OPN5-KLH protein), and the control group (CS and CL groups) was injected at the same time with the same dose of OPN5-uncontained blank vaccine. The group of CS (900 lux), OPN5 (600 lux), and CL (600 lux) lasted for 40 d in 12 L:12 D photoperiods, respectively. Then, the groups of CS, OPN5, and CL subsequently received 12 L:12 D, 12 L:12 D, and 17 L:7 D light treatments for 33 d, respectively. The ducks were caged in 3 constant rooms with the same feeding conditions for each group, free water, and limited feeding (150 g per duck each day). Duck serum and tissue samples were collected at d 40, d 62, and d 73 (n = 12). It was found that before prolonged light, the group of immunization (group OPN5) and the group of strong light intensity (group CS) were higher than the group of CL in egg production. Subsequent to prolonged light, the group CL in egg production rose about the same as the group immunization, while the strong light group (group CS) was lower. Group OPN5 increased the ovarian index of ducks, and both the immunization of group OPN5 and group CL (extended light) increased the thickness of the granular layer and promoted the secretion of E2, P4, LH, and PRL hormones. Compared with group CS, group CL and OPN5 increased the mRNA level and protein expression of OPN5 in the hypothalamus on d 62 and d 73 (P < 0.05). The gene or protein expression patterns of GnRH, TRH, TSHβ, DIO2, THRβ, VIP, and PRL were positively correlated with OPN5, whereas the gene expression patterns of GnIH and DIO3 were negatively correlated with OPN5. The results showed that immunization against OPN5 could activate the corresponding transmembrane receptors to promote the expression of OPN5, up-regulate the expression of TSHβ and DIO2, and then regulate the HPG axis-related genes to facilitate the follicular development of Shan Partridge ducks. In addition, in this experiment, prolonging the photoperiod or enhancing the light intensity could also enhance follicle development, but the effect was not as significant as immunizing against OPN5. Our results will offer beneficial data and more supportive shreds of evidence in favor of elucidating the role of OPN5 in relation to photoperiods and reproduction.

Characterization of reproductive hormones and related gene expression in the hypothalamus and pituitary gland in the egg-laying interval in White King pigeon

The egg-laying interval (LI) directly reflects the laying performance of breeding pigeons, influenced by reproductive hormones. This study aimed to assess reproductive hormone levels in serum and the expression of related genes and their receptors in the hypothalamus and pituitary gland in 4 stages: first (LI1), third (LI3), fifth (LI5), and seventh (LI7) days. The results showed that serum gonadotropin-releasing hormone (GnRH) level decreased from LI1 to LI7 (P < 0.01) and peaked in LI1. The serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels stayed at high levels from LI1 to LI5. The FSH level decreased slightly from LI5 to LI7 (P > 0.05), but the LH level decreased rapidly (P < 0.01). The prolactin (PRL) levels significantly increased in LI5 (P < 0.01) compared with LI1 and then stayed at a high level. The GnRH1 expression in the hypothalamus had no significant change in LI (P > 0.05). However, the GnRHR first decreased from LI1 to LI3 (P < 0.05) and then increased. The FSH mRNA level in the pituitary gland decreased from LI1 to LI3 and slightly increased in LI5 (P > 0.05). The change pattern of FSHR was similar to that of FSH and peaked in LI5 (P < 0.05). The LH expression level was the highest in LI5 and significantly higher than that in LI3 and LI7 (P < 0.05). However, the LHR mRNA level decreased in LI (P < 0.05). The expression patterns of PRL and PRLR were similar; they were upregulated in LI and peaked in LI7 (P < 0.01). The expression pattern of GnRHR was similar to that of FSH, LH, and FSHR, suggesting the critical role of GnRHR in LI. Furthermore, the expression levels of these genes peaked in LI5, closely correlating with the maturation of the first largest follicle in pigeons. PRL-PRLR signaling inhibited GnRH activity to promote ovulation. This study provided a basis for further investigating the molecular mechanisms underlying the regulation of reproduction in pigeons.

Effects of gonadotropin-inhibitory hormone on testicular development and reproduction-related gene expression in roosters

Gonadotropin-inhibitory hormone (GnIH) plays a crucial role in regulating reproduction in the hypothalamus of poultry and has been intensely investigated since its discovery. This study aimed to assess the effects of GnIH on testicular development, as well as on reproduction-related hormone release and gene expression levels in roosters. The administration of exogenous GnIH resulted in a significant reduction in testis weight, testis volume and semen quality (p < 0.05). Additionally, exogenous GnIH significantly up-regulates the expression of GnIH, and down-regulates the expression of PRL (p < 0.05). GnIH application also decreased the GnRH, vasoactive intestinal peptide (VIP) and luteinizing hormone β subunit(LHβ)gene expression levels. Meanwhile, by neutralizing the effects of endogenous GnIH through immunization, testicular development on day 150 in roosters was significantly promoted. Compared to the control condition, GnIH immunization significantly down-regulated the expression of the VIP and PRL genes (p < 0.05). In conclusion, we found that exogenous GnIH treatment inhibited testicular development, reduces PRL gene expression, and suppressed reproductive performance in roosters. Conversely, GnIH immunization down-regulated VIP and PRL genes, activates the reproductive system, and promotes the reproductive activity and testicular development of roosters.

Whole Genome Resequencing Identifies Single-Nucleotide Polymorphism Markers of Growth and Reproduction Traits in Zhedong and Zi Crossbred Geese

The broodiness traits of domestic geese are a bottleneck that prevents the rapid development of the goose industry. To reduce the broodiness of the Zhedong goose and thus improve it, this study hybridized it with the Zi goose, which has almost no broody behavior. Genome resequencing was performed for the purebred Zhedong goose, as well as the F2 and F3 hybrids. The results showed that the F1 hybrids displayed significant heterosis in growth traits, and their body weight was significantly greater than those of the other groups. The F2 hybrids showed significant heterosis in egg-laying traits, and the number of eggs laid was significantly greater than those of the other groups. A total of 7,979,421 single-nucleotide polymorphisms (SNPs) were obtained, and three SNPs were screened. Molecular docking results showed that SNP11 located in the gene NUDT9 altered the structure and affinity of the binding pocket. The results suggested that SNP11 is an SNP related to goose broodiness. In the future, we will use the cage breeding method to sample the same half-sib families to accurately identify SNP markers of growth and reproductive traits.

OPN5 Regulating Mechanism of Follicle Development Through the TSH-DIO2/DIO3 Pathway in Mountain Ducks Under Different Photoperiods

Abstract: Photoperiod is an important environmental factor that influence seasonal reproduction behavior in bird. Birds translates photoperiodic information into neuroendocrine signals through deep brain photoreceptors (DBPs). OPN5 has been considered as candidate DBPs involving in regulation of seasonal reproduction in birds. However, little is known about the effect of OPN5 in non-seasonal breeding birds. Thus, we pondered on whether OPN5 regulating follicular development through TSH-DIO2/DIO3 system responds to different photoperiods in non-seasonal laying ducks. As an ideal non-seasonal breeding bird, a total of 120 mountain ducks were randomly divided into three groups and treated respectively to a different photoperiod: group S (8 L:16D), group C (17 L:7D), and group L (24 L:0D). The ducks were caged in a fully enclosed shelter with the same feeding conditions for each group, free water and limited feeding (150 g per duck each day). Samples were collected from each group at d 0, d 5, d 8, d 20, and d 35 (n = 8). The ducks in 24 h photoperiod had the highest laying rate and the lowest feed-to-egg ratio, while the ducks in 8 h photoperiod had the lowest laying rate and the highest feed-to-egg ratio. Long-day photoperiod for 24 h significantly increased the ovarian index and GnRH, LH, E2, and P4 levels in serum; short-day photoperiod for 8 h increased testosterone levels in serum. Compared with 8 h photoperiod, long-day photoperiod significantly or highly significantly increased the mRNA level and protein expression of OPN5 in the hypothalamus of long-day photoperiod on d 35 (p &lt; 0.05). The gene or protein expression patterns of GnRH, TRH, TSHβ, DIO2, THRβ, VIP, and PRL were positively correlated with OPN5, whereas the gene expression patterns of GnIH and DI O 3 were negatively correlated with OPN5. The results revealed that OPN5 mediated the effect of light on follicular development through the TSH-DIO2/DIO3 pathway, the expression of OPN5 increased with light duration and improved the efficiency of the HPG axis to promote follicular development in mountain ducks.

The effect of light on follicular development in laying hens

OBJECTIVE

The oxidative stress status and changes of chicken ovary tissue after shading were studied, to determine the mechanism of the effect of shading on follicular development.

METHODS

Twenty healthy laying hens (40 weeks old) with uniform body weight and the same laying rate were randomly divided into two groups (the shading group and normal light group). In the shading group, the cage was covered to reduce the light intensity inside the cage to 0 without affecting ventilation or food intake. The normal lighting group received no additional treatment. After 7 days of shading, oxidative stress related indicators and gene expression were detected.

RESULTS

Analysis of paraffin and ultrathin sections showed that apoptosis of ovarian granulosa cells (GCs) increased significantly after light shading. Enzyme linked immunosorbent assay results revealed that the levels of total antioxidant capacity, malondialdehyde, superoxide dismutase (SOD), glutathione, catalase (CAT), and other substances in the sera, livers, ovaries, and follicular GCs of laying hens increased significantly after shading for 7 days; and reactive oxygen species (ROS) levels in the livers of laying hens also increased significantly. ROS in the serum, ovarian and GCs also increased. After shading for 7 days, the levels of 8-hydroxy-2 deoxyguanosine in the sera and ovarian tissues of laying hens increased significantly. Cell counting kit-8 detection showed that the proliferation activity of GCs in layer follicles decreased after shading for 7 days; the expression level of the anti-apoptotic gene B-cell lymphoma-2 in ovarian tissue and follicular GCs was significantly reduced, and the expression levels of pro-apoptotic caspase 3 (casp3), and SOD, glutathione peroxidase 2 (GPX2), and CAT were all significantly increased.

CONCLUSION

Oxidative stress induced by shading light has a serious inhibitory effect on follicular development during reproduction in laying hens.

Meta-analysis: Supplementary artificial light and goose reproduction

Photoperiod affects poultry reproduction, and in birds, photoperiod regulation is a complex physiological process. In modern poultry production, lighting management has become an important and effective management approach for increasing egg production. Geese are domesticated fowl and in many goose production enterprises animals are allowed to roam in outside pens during the day and are housed indoors at night, so the animals can be exposed to artificial lighting during the night periods. Supplementary artificial lighting resulted in improved reproduction in some studies, but reports have been inconsistent. To evaluate the results from previous studies of supplementary lighting on goose egg production, a meta-analysis was conducted to determine optimal supplementary artificial lighting regimens for geese egg production. Results indicated supplementary artificial light increases mean egg production, the length of the period of egg production before there is cessation of egg production capacity, and fertility. In summary, there were evaluations of data from five studies focused on White Roman geese in the meta-analysis conducted in the present study, however, examination of more breeds is necessary to make more definitive assessments of the findings from this meta-analysis.

Effect and molecular regulatory mechanism of monochromatic light colors on the egg-laying performance of Yangzhou geese

Photoperiodic control is essential for manipulating the reproductive performance of avian species. This study was conducted to assess the neuroendocrine mechanisms that regulate reproductive functions of Yangzhou geese when there are different monochromatic light colors from light emitter diode (LED) sources. A flock of geese was divided into four groups with white, red, blue, and green light treatments being imposed. The results indicated that peak laying rates and reproductive performance were greater in geese treated with white or red as compared with blue or green light treatments. The fertilization rate of eggs and hatchability of fertilized eggs were greater with the white or red as compared with blue or green light treatments. There was a greater abundance of OPN5, Dio2, c-Fos, and GnRH-I mRNA in the hypothalamus earlier in the treatment period and abundances of these hypothalamic factors were greater with the white or red light treatments. Abundances of pituitary LH beta and FSH beta mRNA increased at a lesser rate with the blue or green light treatments and were in greater abundances with the white or red light treatments. The lighting regimen also resulted in photo-refractoriness with there being greater abundances of GnIH, VIP, and PRL mRNA with the use of white or red light treatments. The results indicate that the use of white or red monochromatic lights while imposing a long photoperiod of 11 h daily could result in sustaining functions of the reproductive system of Yangzhou geese for considerably longer times, thus, resulting in greater egg-laying performance.

Analyses of mathematical models for Yangzhou geese egg-laying curves

Mathematical models of the egg-laying curves for Yangzhou geese exposed to both natural and artificial photoperiods were established to optimise the parameters for maximising geese reproductive performance and for the development of precision feeding methods. With the natural photoperiod, egg-laying starts in autumn when daily photoperiod decreases, but accelerates after the winter solstice, and reaches the peak in spring when photoperiod increases. An accumulating model was constructed based on the hypothesis that the egg-laying capacity of geese was determined by two components of the photoperiod: photo-stimulation and photo-inhibition. In addition, a second segmented model was constructed based on the hypothesis that the photo-stimulation only occurred with lengthening photoperiods after the winter solstice, and the lesser laying rate in autumn could be attributed to the non-photo-dependent animal-husbandry technologies. This model consists of a logistic model before the winter solstice, and an accumulating model after this solstice. The use of the logistic and accumulating resulted in more precise predictions that occurred with use of Model 1 with a greater R² and lesser RMSE, AIC and BIC. Likewise, the egg-laying curves when there was consideration of artificial photoperiods could also be constructed with consideration of stimulatory and inhibitory photoperiodic effects. The model consists of an initial logistic and subsequently a quadratic polynomial model. With use of this model, there is consideration of changes in egg-laying patterns when there is a fixed photoperiod, with the model parameters reflecting the effects by photoperiod control-programs and age of the geese. In conclusion, new mathematical models have been developed to best fit egg-laying curves when there are both natural and artificial photoperiods. These models can contribute to development of precision-feeding technologies for breeding geese in future.