The aim of this study was to compare egg quality, carcass, meat characteristics, and bone properties of Taihang chickens in 2 different housing systems at various ages. A total of 168 birds were selected and randomly allocated to 2 groups at 23 wks and raised in conventional cage ( CC ) or flattening on floor ( FF ) housing system, respectively. FF hens' egg weight, albumen height, and Haugh unit were higher ( P < 0.05), and yolk weight was lower ( P < 0.001) than those of the CC hens. Egg quantity of FF hens was higher than that of the CC hens ( P < 0.01). The FF hens' weight ( P < 0.05) and breast meat percent ( P < 0.01) were higher than those of the CC hens. The highest live body and carcass weight were observed at 57 wk (both P < 0.01), whereas the highest semieviscerated percentage ( P < 0.01) and meat weight of breast and thigh ( P < 0.05) were shown at 49 wk. The highest eviscerated percentage and thigh meat were displayed at 41 and 32 wk, respectively ( P < 0.01). For meat color, the lightness of both breast and thigh meat in the FF group was significantly reduced compared with those of the CC group ( P < 0.01 and P < 0.05). FF hens' humerus weight and breaking strength (both P < 0.01) and tibia breaking strength ( P < 0.05) were significantly higher than those of the CC hens. Femur breaking strength was significantly affected by hens' age ( P < 0.01). Egg weight, albumen height, Haugh unit, yolk color (all P < 0.01), pH of thigh meat, semieviscerated, and eviscerated weight (all P < 0.05) were influenced by the interaction of housing system and age, whereas no change in moisture loss rate, meat color, shearing force, and bone quality was found ( P > 0.05). In summary, in the 2 housing systems, hens' age and their interaction could affect slaughter performance, quality of egg, meat, and bone of Taihang chickens. In addition, the results of the present study support a theoretical basis for the development and utilization of Taihang chickens in accordance with the FF system.
Melatonin is a key regulator of follicle granular cell maturation and ovulation. The mammalian target of rapamycin ( mTOR ) pathway plays an important role in cell growth regulation. Therefore, our aim was to investigate whether the mTOR signaling pathway is involved in the regulation of melatonin-mediated proliferation and apoptotic mechanisms in granulosa cells. Chicken follicle granular cells were cultured with melatonin (0, 2, 20, or 200 μmol/L) for 48 h. The results showed that melatonin treatment enhanced proliferation and suppressed apoptosis in granular cells at 20 μmol/L and 200 μmol/L ( P < 0.05) by upregulation of cyclin D1 ( P < 0.01) and Bcl-2 ( P < 0.01) and downregulation of P21, caspase-3, Beclin1, and LC3-II ( P < 0.01). The effects resulted in the activation of the mTOR signaling pathway by increasing the expression of avTOR, PKC, 4E-BP1, S6K ( P < 0.05), p-mTOR, and p-S6K. We added an mTOR activator and inhibitor to the cells and identified the optimal dose (10 μmol/L MHY1485 and 100 nmol/L rapamycin) for subsequent experiments. The combination of 20 μmol/L melatonin and 10 μmol/L MHY1485 significantly enhanced granulosa cell proliferation ( P < 0.05), while 100 nmol/L rapamycin significantly inhibited proliferation and enhanced apoptosis ( P < 0.05), but this action was reversed in the 20-μmol/L melatonin and 100-nmol/L rapamycin cotreatment groups ( P < 0.05). This was confirmed by mRNA and protein expression that was associated with proliferation, apoptosis, and autophagy ( P < 0.05). The combination of 20 μmol/L melatonin and 10 μmol/L MHY1485 also activated the mTOR pathway upstream genes PI3K, AKT1, and AKT2 and downstream genes PKC, 4E-BP1, and S6K ( P < 0.05), as well as protein expression of p-mTOR and p-S6K. Rapamycin significantly inhibited the mTOR pathway–related genes mRNA levels ( P < 0.05). In addition, activation of the mTOR pathway increased melatonin receptor mRNA levels ( P < 0.05). In conclusion, these findings demonstrate that melatonin regulates chicken granulosa cell proliferation and apoptosis by activating the mTOR signaling pathway via its receptor.
To investigate the regulatory mechanism of the follicular–luteal phase transition in Turpan black sheep (Ovis aries), the genome‐wide expression patterns of microRNAs (miRNAs) and genes were investigated in ovaries of six sheep (3 years and single lamb with 3 consecutive births) during follicular and luteal phases of the oestrous cycle. Bioinformatic analysis was used to screen potential miRNAs and genes related to Turpan black sheep ovarian function. RT‐qPCR was used to validate the sequencing results. In total, we identified 139 known and 71 novel miRNAs in the two phases with miRNA‐seq, and a total of 19 miRNAs were significantly differentially expressed, of which 7 were up‐regulated and 12 were down‐regulated in the follicular phase compared with luteal phase. A total of 150 genes were significantly differentially expressed, including 63 up‐regulated and 87 down‐regulated in the follicular phase compared with the luteal phase by RNA‐seq data analysis. Those DEGs were significantly enriched in 103 GO terms and several KEGG pathways, including metabolic pathway, ovarian steroidogenesis, steroid hormone biosynthesis and oestrogen signalling pathway. In addition, we created a miRNA–mRNA regulatory network to further elucidate the mechanism of follicular–luteal transition. Finally, we identified key miRNAs and genes including miR‐143, miR‐99a, miR‐150, miR‐27a, miR‐125b, STAR, STAT1, which might play crucial roles in reproductive hormone biosynthesis and follicular development. The miRNA–mRNA interactive network clearly illustrates molecular basis involving in follicular–luteal transition.
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