Effects of Oxidative Stress on the Autophagy and Apoptosis of Granulosa Cells in Broody Geese

Broodiness is an unfavorable trait associated with the cessation of egg laying. Studies have found that excessive granulosa cell apoptosis and autophagy occur during goose broodiness. Other studies have also confirmed that oxidative stress is an important cause of apoptosis and autophagy. However, whether oxidative stress occurs during goose broodiness and whether this oxidative stress causes apoptosis and autophagy have not been fully elucidated. In this study, we investigated the effects of oxidative stress on the autophagy and apoptosis of granulosa cells in broody geese. The results showed higher mRNA expression of genes related to antioxidative stress responses (GPX, SOD-1, SOD-2, COX-2, CAT and hsp70) in pre-broody and broody geese than in laying birds. In addition, increased levels of granulosa cell apoptosis and autophagy were observed in pre-broody geese than in laying geese. Additionally, granulosa cells treated with H₂O₂ exhibited increased apoptosis and autophagy in vitro, and these effects were responsible for goose granulosa cell death. Moreover, vitamin E treatment effectively protected granulosa cells from H₂O₂-induced oxidative stress by inhibiting ROS production. Correspondingly, granulosa cell apoptosis and autophagy were greatly alleviated by vitamin E treatment. Together, our results demonstrated serious oxidative stress and granulosa cell apoptosis and autophagy in broody geese, and oxidative stress promoted apoptosis and autophagy. Vitamin E alleviated the autophagy and apoptosis of granulosa cells by inhibiting oxidative stress.

MiR-34c-5p promotes granulosa cells apoptosis by targeting Bcl2 in broody goose (Anser cygnoides)

Goose (Anser cygnoides) are highly broody with low egg production, and large number of granulosa cells undergo apoptosis during broodiness. Our previous study has found that miR-34c-5p was highly abundant in the ovary of goose with broodiness phenotype. However, the mechanism that miR-34c-5p regulates granulosa cells function remains unclear. Here, we demonstrated that broody goose had higher levels of miR-34c-5p than that in laying goose by qRT-PCR. The dual luciferase reporter assay showed that Bcl2 was identified as a direct target of miR-34c-5p, which could be negatively regulated by miR-34c-5p. Furthermore, over-expression of miR-34c-5p significantly increased the rate of apoptosis and slowed down the proliferation of granulosa cells by inhibiting the Bcl2 expression, whereas the opposite trend was obtained when granulosa cells were supplemented with miR-34c-5p inhibitors. In addition, Bcl2 mRNA level was lower in goose with a brooding phenotype than that in goose with an egg-laying phenotype. Taken together, the data suggested that miR-34c-5p regulated granulosa cells apoptosis and brooding behavior by targeting Bcl2, which not only contribute to reveal the potential mechanism of miR-34c-5p underlying granulosa cells apoptosis in goose, but also provides an effective strategy to reduce the incidence of broodiness and improve the egg production.

Genetic parameters for clutch and broodiness traits in turkeys (Meleagris Gallopavo) and their relationship with body weight and egg production

The objective of this study was to estimate phenotypic and genetic parameters for clutch and broodiness (BR) traits in turkeys and their relationship with body weight and egg production. Data on dam line hens was available and included: body weight at 18 wk of age (BW18), body weight at lighting (BWL, 29 to 33 wk), age at first egg (AFE), egg number (EN), rate of lay (RL), clutch length (CL), maximum clutch length (MCL), pause length (PL), maximum PL (MPL) and BR. BR was defined as the average number of consecutive pause days between clutches that was higher than the average PL per hen. Heritability estimates for BW18 and BWL were 0.50 and 0.53, respectively. The heritability for egg production, clutch, and pause traits varied from low (MPL = 0.15; BR = 0.15) to moderate (AFE = 0.22; EN = 0.28; RL = 0.29; CL = 0.21; MCL = 0.27; PL = 0.25). Genetic correlations were negative between body weight traits and EN (r_{g (BW18, EN)} = −0.27; r_{g(BWL, EN)} = −0.33) and CL (r_{g(BW18, CL)} = −0.40; r_{g(BWL, CL)} = −0.33). BR was negatively genetically correlated with EN (r_{g(BR, EN)} = −0.85) and CL (r_{g(BR, CL)} = −0.30), and positively genetically correlated with PL (r_{g(BR, PL)} = 0.93) and AFE (r_{g(BR, AFE)} = 0.21). EN had a positive (0.73) and a negative (−0.84) genetic correlation with CL and PL, respectively. Overall, the results of this study confirmed the negative (unfavorable) correlations between egg production and body weight. Despite unfavorable genetic and phenotypic correlations between egg production traits and those relating to BR, the inclusion of BR in a selection program through incorporation of clutch length traits and pause length traits is feasible. Integration of either clutch length traits or pause length traits in a selection index is likely to increase egg number while decreasing broodiness.

Egg-laying and brooding stage-specific hormonal response and transcriptional regulation in pituitary of Muscovy duck (Cairina moschata)

Broodiness is an interesting topic in reproductive biology for its reduced egg production. The strong brooding trait of Muscovy duck has become a major factor restricting the development of its industry. Broody phenotype and environmental factors influencing broodiness in poultry have been extensively studied, but the molecular regulation mechanism of broodiness remains unclear. In this research, the Muscovy duck reproductive endocrine hormones and pituitary transcriptome profiles during egg-laying phases (LP) and brooding phases (BP) were studied. During BP (n = 19), prolactin (PRL) levels was higher, while progesterone (P4) and estradiol (E2) were lower as compared to ducks during their LP (n = 20) (P < 0.01). We then examined the pituitary transcriptome of Muscovy duck at the 2 reproductive stages. A total of 398 differentially expressed genes included 20 transcription factors were identified (fold change ≥ 1.5, P < 0.01). There were 109 upregulated and 289 downregulated genes at brooding phases (n = 6) compared with egg-laying phases (n = 6). Real-time quantitative PCR analysis was carried out to verify the transcriptome results. The present study suggested that neuroactive ligand-receptor interaction pathway, calcium signaling pathway, and response to steroid hormones biological process are critical for controlling broodiness in the ducks. Further analysis revealed that SHH, PTGS2, RLN3, and transcription factor AP-1 may act as central signal modulators of hormonal and behavioral regulation mechanism associated with broodiness.

Goose broodiness is involved in granulosa cell autophagy and homeostatic imbalance of follicular hormones

Broodiness is observed in most domestic fowls and influences egg production. The goose is one of the most important waterfowls, having strong broody behavior. However, whether autophagy and follicular internal environment play a role in the broodiness behavior of goose is unknown. In this report, we analyzed the follicular internal environment and granulosa cell autophagy of goose follicles. The results show that the contents of hormones, including prolactin (PRL), progesterone (P4), and estradiol (E2), increased in broody goose follicles. Most importantly, the level of granulosa cell autophagy in broody goose follicles was elevated, detected by electron microscopy and western blotting. Also, the expressions of positive regulators of autophagy, including miR-7, miR-29, miR-100, miR-181, PRLR, LC3, p53,Beclin1, Atg9, and Atg12, were up-regulated and the expressions of negative regulators of autophagy, including miR-34b and miR-34c, were down-regulated in broody goose follicles. Our results suggest that goose broodiness is involved in increased granulosa cell autophagy and homeostasis imbalance of internal environment in the follicles. This work contributes to our knowledge of goose broodiness and may influence egg production.

Hypothalamic Agouti-Related Peptide mRNA is Elevated During Natural and Stress-Induced Anorexia

As part of their natural lives, animals can undergo periods of voluntarily reduced food intake and body weight (i.e. animal anorexias) that are beneficial for survival or breeding, such as during territorial behaviour, hibernation, migration and incubation of eggs. For incubation, a change in the defended level of body weight or 'sliding set point' appears to be involved, although the neural mechanisms reponsible for this are unknown. We investigated how neuropeptide gene expression in the arcuate nucleus of the domestic chicken responded to a 60-70% voluntary reduction in food intake measured both after incubation and after an environmental stressor involving transfer to unfamiliar housing. We hypothesised that gene expression would not change in these circumstances because the reduced food intake and body weight represented a defended level in birds with free access to food. Unexpectedly, we observed increased gene expression of the orexigenic peptide agouti-related peptide (AgRP) in both incubating and transferred animals compared to controls. Also pro-opiomelanocortin (POMC) mRNA was higher in incubating hens and significantly increased 6 days after exposure to the stressor. Conversely expression of neuropeptide Y and cocaine- and amphetamine-regulated transcript gene was unchanged in both experimental situations. We conclude that AgRP expression remains sensitive to the level of energy stores during natural anorexias, which is of adaptive advantage, although its normal orexigenic effects are over-ridden by inhibitory signals. In the case of stress-induced anorexia, increased POMC may contribute to this inhibitory role, whereas, for incubation, reduced feeding may also be associated with increased expression in the hypothalamus of the anorexigenic peptide vasoactive intestinal peptide.

Persistent effect of broody hens on behaviour of chickens

We reported previously that behavioral development of chicks was promoted remarkably by the presence of a broody hen. Here we report that these effects at an early age persist after maturity. A total of 60 female chicks were randomly assigned to one of two treatment groups: six pens with five chicks (brooded group) each were reared by a broody hen and six pens with five chicks (non-brooded group) each were provided with an infrared heating lamp. We evaluated the persistent effects of broody hens by measures of behavior, physical condition and production at 9, 16, 35 and 55 weeks of age. The numbers of threatening, aggressive pecking, fighting and severe feather pecking behaviors were higher in non-brooded than in brooded chickens (all P < 0.05). Egg production was lower in brooded than in non-brooded chickens (P < 0.05), while the number of brooding chickens was higher in the brooded than in the non-brooded group (P < 0.05). In conclusion, the presence of broody hens at an early stage of chicks' lives has a persistent effect on behavior. Although brooded chickens showed more brooding and lower egg production than non-brooded chickens, feather pecking and aggressive interaction were decreased in brooded hens.