In this study, we explored the effect of dietary lead nitrate on zootechnical performance, egg quality, accumulation of ovarian plumbum (Pb), follicular atresia rate, and ovarian oxidative stress in laying hens. Furthermore, the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling molecule was studied to reveal the molecular mechanism of the stress. A total of 512 Hy-Line Brown laying hens aged 40 wk were randomly allocated to 4 groups (with 8 pens per group and 16 hens per pen). The Pb concentrations used to treat the 4 groups were 3.20, 33.20, 63.20, and 93.20 mg/kg. The results revealed that dietary Pb exposure significantly linearly reduced the zootechnical performance (P < 0.01) but significantly linearly increased the feed conversion ratio (P < 0.01). The dietary Pb exposure significantly linearly reduced the Haugh units (P < 0.01), albumen height (P < 0.01), eggshell thickness (P < 0.01), and eggshell strength (P < 0.01). In addition, the dietary Pb exposure significantly enhanced the follicular atresia rate (P < 0.01). After dietary Pb exposure, superoxide dismutase (P < 0.01) and glutathione peroxidase (GSH-Px) (P < 0.01) activities and glutathione (P < 0.01) contents were significant decreased quadratically, and there were significant linear decreases in the activities of catalase (CAT) (P < 0.01) and glutathione reductase (GR) (P < 0.01), whereas malondialdehyde content was significantly linearly increased (P < 0.01). In addition, except for manganese superoxide dismutase, the gene expressions of copper-zinc superoxide dismutase (P < 0.01), CAT (P < 0.01), and GR (P < 0.01) were significant decreased linearly. In addition, there were significantly quadratic decreases in the mRNA expressions of GSH-Px (P < 0.01) and Nrf2 (P < 0.01). By way of contrast, the Kelch-like ECH-associated protein 1 (Keap1) gene expression was significantly linearly increased (P < 0.01). In conclusion, dietary Pb exposure could induce oxidative stress by impairing the Nrf2-Keap1 signal pathway in the ovaries of laying hens.

中文翻译：

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不同膳食铅中毒对蛋鸡生产性能和卵巢的影响。

在本研究中，我们探讨了日粮中硝酸铅对蛋鸡动物技术性能、鸡蛋质量、卵巢铅 (Pb) 积累、卵泡闭锁率和卵巢氧化应激的影响。此外，还研究了核因子红细胞2相关因子2（Nrf2）信号分子，以揭示应激的分子机制。共有 512 只 40 周龄海兰褐蛋鸡随机分为 4 组（每组 8 栏，每栏 16 只母鸡）。用于治疗 4 组的 Pb 浓度分别为 3.20、33.20、63.20 和 93.20 mg/kg。结果显示，日粮中的铅暴露显着线性降低了动物技术性能（P < 0.01），但显着线性增加了饲料转化率（P < 0.01）。膳食铅暴露显着线性降低哈夫单位（P < 0.01）、蛋白高度（P < 0.01）、蛋壳厚度（P < 0.01）和蛋壳强度（P < 0.01）。此外，膳食Pb暴露显着增加了卵泡闭锁率（P < 0.01）。膳食Pb暴露后，超氧化物歧化酶（P < 0.01）和谷胱甘肽过氧化物酶（GSH-Px）（P < 0.01）活性和谷胱甘肽（P < 0.01）含量呈二次方显着下降，过氧化氢酶活性呈显着线性下降。 （CAT）（P < 0.01）和谷胱甘肽还原酶（GR）（P < 0.01），而丙二醛含量显着线性增加（P < 0.01）。此外，除锰超氧化物歧化酶外，铜锌超氧化物歧化酶（P < 0.01）、CAT（P < 0.01）、GR（P < 0.01）基因表达量均显着线性下降。此外，GSH-Px（P < 0.01）和Nrf2（P < 0.01）的mRNA表达显着呈二次下降。相比之下，Kelch 样 ECH 相关蛋白 1 (Keap1) 基因表达显着线性增加 (P < 0.01)。总之，饮食中的 Pb 暴露可能通过损害蛋鸡卵巢中的 Nrf2-Keap1 信号通路来诱导氧化应激。