Roushdy Elshimaa M, Zaglool Asmaa W, Hassan Fardos A M
Animal Wealth Development Department, Faculty of Veterinary Medicine, Zagazig University, Zagazig, 44511, Egypt.
Trop Anim Health Prod. 2020 Nov;52(6):3685-3696. doi: 10.1007/s11250-020-02405-4. Epub 2020 Sep 25.
The current study was conducted to investigate the impact of thermal stress on growth performance, blood biomarkers, metabolic hormones, immunological response, antioxidant activity, and expression of stress-related genes in broilers. One hundred and fifty one-day-old chicks (Ross 308) were utilized in this work. On the 21st day of age, birds were subjected to three environmentally controlled treatments with five replicate pens of 10 birds per each, representing an initial density of 10 birds/m-control: reared in a thermoneutral condition; THS and THS exposed to 4 and 6 h of daily thermal stress at 40 ± 1 °C, respectively, until the 42 days of age. The results demonstrated that thermal stress for 4 and 6 h significantly reduced (P < 0.001) daily weight gain, daily feed intake, blood leukocyte and lymphocyte counts, serum immunoglobulins (IgM, IgA, IgG), and insulin-like growth factor-1 (IGF-1), while serum levels of aspartate aminotransferase, alanine aminotransferase, glucose, cholesterol, low-density lipoprotein, and lactate dehydrogenase were elevated relative to the thermoneutral group. Additionally, the corticosterone level and the ratio of heterophil:lymphocyte increased significantly (P < 0.001) in thermal-stressed groups. The antioxidant enzymes were affected by thermal stress as represented by a significant decrease in the activity of serum catalase (CAT) and glutathione peroxidase (GSH-Px) along with an increase in malonaldehyde concentration. Thermal stress affected gene expression by upregulating heat shock protein 70, heat shock factors 1 and 3, nuclear factor kappa B, interleukin-4, and uncoupling protein, and downregulating GSH-Px, CAT, and IGF-1 transcript levels. However, no changes were observed in interleukin-2 expression levels. It can be concluded that thermal stress destructively influences productivity, physiological status, and gene expression by upregulating heat shock protein 70, heat shock factors 1 and 3, nuclear factor kappa B, interleukin-4, and uncoupling protein, and downregulating GSH-Px, CAT, and IGF-1 transcript levels of broiler chickens.
本研究旨在探讨热应激对肉鸡生长性能、血液生物标志物、代谢激素、免疫反应、抗氧化活性以及应激相关基因表达的影响。本研究选用了150只1日龄雏鸡（罗斯308）。在21日龄时，将鸡分为三种环境控制处理组，每组设5个重复栏，每栏10只鸡，初始饲养密度为10只/m²：对照组：在热中性条件下饲养；THS1组和THS2组分别在40±1°C的环境中每天接受4小时和6小时的热应激处理，直至42日龄。结果表明，4小时和6小时的热应激显著降低了（P<0.001）日增重、日采食量、血液白细胞和淋巴细胞计数、血清免疫球蛋白（IgM、IgA、IgG）以及胰岛素样生长因子-1（IGF-1），而相对于热中性组，血清天冬氨酸转氨酶、丙氨酸转氨酶、葡萄糖、胆固醇、低密度脂蛋白和乳酸脱氢酶水平升高。此外，热应激组的皮质酮水平以及异嗜性粒细胞与淋巴细胞的比例显著增加（P<0.001）。抗氧化酶受到热应激的影响，表现为血清过氧化氢酶（CAT）和谷胱甘肽过氧化物酶（GSH-Px）活性显著降低，同时丙二醛浓度升高。热应激通过上调热休克蛋白70、热休克因子1和3、核因子κB、白细胞介素-4和解偶联蛋白，并下调GSH-Px、CAT和IGF-1转录水平来影响基因表达。然而，白细胞介素-2的表达水平未观察到变化。可以得出结论，热应激通过上调热休克蛋白70、热休克因子1和3、核因子κB、白细胞介素-4和解偶联蛋白，并下调肉鸡的GSH-Px、CAT和IGF-1转录水平，对其生产性能、生理状态和基因表达产生破坏性影响。
