The purpose of the present study was to investigate the effects of dietary alpha-lipoic acid (ALA) supplementation on the reproductive performance of aged breeder roosters. Sixteen 50-wk-old ROSS 308 breeder roosters were randomly allocated to two groups: roosters received a basal diet (CON), or a basal diet supplemented with 300 mg/kg of ALA (ALA). The results indicated that dietary ALA supplementation significantly increased sperm concentration, motility, viability, and membrane functional integrity. ALA also dramatically increased seminiferous tubule epithelial height (SEH) and testis scores. The ALA group had a higher serum concentration of testosterone than the CON group. ALA supplementation remarkably increased total antioxidant capacity (T-AOC), the enzyme activities of glutathione peroxidase (GPx), and catalase (CAT) in the testes; following a decrease in malondialdehyde (MDA) levels. In addition, we noted significant upregulation of Nrf2 mRNA and protein expression of and mRNA expression of its Downstream Genes (GPx1, NQO1, and GCLC), as well as significant downregulation of Keap1 mRNA expression in testicular tissue of aged roosters with ALA supplementation. The protein expression of Caspase 3 was downregulated and the protein expression of proliferating cell nuclear antigen (PCNA) was upregulated by ALA supplementation. The mRNA expression of spermatogenesis-related genes (ER1, AKT1, and Cav1) were markedly augmented in the ALA group compared with the CON group. In conclusion, dietary ALA supplementation enhanced the testicular antioxidant capacity through the Nrf2-signaling pathway, exerted anti-apoptotic effects, and improved the reproductive performance of aged roosters.

中文翻译：

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膳食 α-硫辛酸补充剂通过抗氧化和抗凋亡作用改善老年种公鸡的精子发生和精液质量

本研究的目的是调查日粮中添加 α-硫辛酸 (ALA) 对老年种公鸡繁殖性能的影响。16 只 50 周龄的 ROSS 308 种公鸡被随机分配到两组：公鸡接受基础饮食 (CON)，或添加 300 mg/kg ALA (ALA) 的基础饮食。结果表明，膳食 ALA 补充剂显着增加了精子浓度、活力、活力和膜功能完整性。ALA 还显着增加了生精小管上皮高度 (SEH) 和睾丸评分。ALA 组的血清睾酮浓度高于 CON 组。补充ALA显着提高了睾丸中的总抗氧化能力（T-AOC）、谷胱甘肽过氧化物酶（GPx）和过氧化氢酶（CAT）的酶活性；随着丙二醛 (MDA) 水平的降低。此外，我们注意到 Nrf2 mRNA 及其下游基因（GPx1、NQO1 和 GCLC）的蛋白质表达和 mRNA 表达显着上调，以及补充 ALA 的老年公鸡睾丸组织中 Keap1 mRNA 表达的显着下调。Caspase 3 的蛋白质表达被下调，增殖细胞核抗原 (PCNA) 的蛋白质表达被 ALA 补充上调。与 CON 组相比，ALA 组精子发生相关基因（ER1、AKT1 和 Cav1）的 mRNA 表达显着增加。总之，膳食 ALA 补充剂通过 Nrf2 信号通路增强了睾丸抗氧化能力，发挥了抗凋亡作用，