This study was conducted to assess the impacts of prolonged fasting (70 and 120 days) on the morphological, biochemical, oxidative stress responses, immune-related gene expression, histopathology, and DNA damage in rainbow trout. Final weight (FW), hepatosomatic index (HSI), and condition factor (CF) significantly decreased in both 70 and 120 days of fasting compared to the pre-fasting group (p < 0.05). Fasting led to a significant reduction in serum blood metabolites (glucose, total protein, triglyceride, T. cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein (LDL)) and endogenous reserves (protein and lipid). However, plasma acetylcholinesterase (AChE) activity, aspartate aminotransferase (AST), alanine aminotransferase (ALT), interleukin (IL1), tumor necrosis factor (TNF1α), and transferrin (TF) increased significantly (p < 0.05). While malondialdehyde (MDA) levels compared to the pre-fasting group increased in the liver and muscle tissues (70 and 120 days), glutathione (GSH) enzyme activities decreased significantly in both tissues (p < 0.05). Histopathologically, both fasting groups (70 and 120 days) when compared to the pre-fasting group led to steatosis, necrosis and degeneration in hepatocytes, inflammation and hyperemia in the liver tissue and hyaline degeneration, atrophy, and inflammation in muscle tissue. Additionally, 8-OHdG levels of the liver and muscle tissues at 120 days’ fasting were more severe according to 70 days’ fasting. Finally, blood, the liver, and muscle tissues may be helpful to assess the impacts of fasting and fasting stress in rainbow trout.

本研究旨在评估长期禁食（70 天和 120 天）对虹鳟鱼形态学、生化、氧化应激反应、免疫相关基因表达、组织病理学和 DNA 损伤的影响。与禁食前组相比，禁食 70 天和 120 天的最终体重 (FW)、肝体指数 (HSI) 和状况因子 (CF) 均显着降低 ( p < 0.05)。禁食导致血清血液代谢物（葡萄糖、总蛋白、甘油三酯、T. 胆固醇、高密度脂蛋白 (HDL) 和低密度脂蛋白 (LDL)）和内源性储备（蛋白质和脂质）显着减少。然而，血浆乙酰胆碱酯酶 (AChE) 活性、天冬氨酸转氨酶 (AST)、丙氨酸转氨酶 (ALT)、白细胞介素 (IL1)、肿瘤坏死因子 (TNF1α) 和转铁蛋白 (TF) 显着增加 ( p  < 0.05)。虽然与禁食前组相比，肝脏和肌肉组织（70 天和 120 天）中的丙二醛 (MDA) 水平增加，但两种组织中的谷胱甘肽 (GSH) 酶活性显着降低（p < 0.05)。组织病理学上，与禁食前组相比，禁食组（70 天和 120 天）均导致肝细胞脂肪变性、坏死和变性，肝组织炎症和充血，肌肉组织透明变性、萎缩和炎症。此外，根据禁食 70 天的情况，禁食 120 天时肝脏和肌肉组织的 8-OHdG 水平更严重。最后，血液、肝脏和肌肉组织可能有助于评估禁食和禁食压力对虹鳟鱼的影响。