High environmental temperatures induce heat stress in broiler chickens, affecting their health and production performance. Several dietary, managerial, and genetics strategies have been tested with some success in mitigating heat stress (HS) in broilers. Developing novel HS mitigation strategies for sustaining broiler production is critically needed. This study investigated the effects of pre-hatch thermal manipulation (TM) and post-hatch baicalein supplementation on growth performance and health parameters in heat-stressed broilers. Six hundred fertile Cobb 500 eggs were incubated for 21 d. After candling on embryonic day (ED) 10, 238 eggs were thermally manipulated at 38.5 °C with 55% relative humidity (RH) from ED 12 to 18, then transferred to the hatcher (ED 19 to 21, standard temperature) and 236 eggs were incubated at a controlled temperature (37.5 °C) till hatch. After hatch, 180-day-old chicks from both groups were raised in 36 pens (n = 10 birds/pen, 6 replicates per treatment). The treatments were: 1) Control, 2) TM, 3) control heat stress (CHS), 4) thermal manipulation heat stress (TMHS), 5) control heat stress supplement (CHSS), and 6) thermal manipulation heat stress supplement (TMHSS). All birds were raised under the standard environment for 21 d, followed by chronic heat stress from d 22 to 35 (32–33 °C for 8 h) in the CHS, TMHS, CHSS, and TMHSS groups. A thermoneutral (22–24 °C) environment was maintained in the Control and TM groups. RH was constant (50% ± 5%) throughout the trial. All the data were analyzed using one-way ANOVA in R and GraphPad software at P < 0.05 and are presented as mean ± SEM. Heat stress significantly decreased (P < 0.05) the final body weight and ADG in CHS and TMHS groups compared to the other groups. Embryonic TM significantly increased (P < 0.05) the expression of heat shock protein-related genes (HSP70, HSP90, and HSPH1) and antioxidant-related genes (GPX1 and TXN). TMHS birds showed a significant increment (P < 0.05) in total cecal volatile fatty acid (VFA) concentration compared to the CHS birds. The cecal microbial analysis showed significant enrichment (P < 0.05) in alpha and beta diversity and Coprococcus in the TMHSS group. Pre-hatch TM and post-hatch baicalein supplementation in heat-stressed birds mitigate the detrimental effects of heat stress on chickens' growth performance, upregulate favorable gene expression, increase VFA production, and promote gut health by increasing beneficial microbial communities.

中文翻译：

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孵化前胚胎热操作和孵化后补充黄芩素可减轻肉鸡的热应激

环境温度高会引起肉鸡热应激，影响其健康和生产性能。一些饮食、管理和遗传学策略已经过测试，在缓解肉鸡热应激 (HS) 方面取得了一些成功。迫切需要制定新的 H2S 缓解策略来维持肉鸡生产。本研究调查了孵化前热控制 (TM) 和孵化后补充黄芩素对热应激肉鸡生长性能和健康参数的影响。600 个可育 Cobb 500 蛋孵化 21 天。在胚胎日 (ED) 10 进行对光检查后，从 ED 12 到 18，在 38.5 °C、55% 相对湿度 (RH) 下对 238 个蛋进行热操作，然后转移到出雏机（ED 19 到 21，标准温度），对 236 个蛋进行热操作。在受控温度（37.5°C）下孵化直至孵化。孵化后，两组 180 日龄的雏鸡在 36 个围栏中饲养（n = 10 只鸡/围栏，每次处理 6 个重复）。治疗方法为：1) 对照，2) TM，3) 控制热应激 (CHS)，4) 热操纵热应激 (TMHS)，5) 控制热应激补充 (CHSS)，以及 6) 热操纵热应激补充 ( TMHSS）。CHS、TMHS、CHSS和TMHSS组的所有鸡均在标准环境下饲养21天，然后从第22天到第35天（32-33°C，8小时）进行慢性热应激。对照组和 TM 组维持热中性（22-24°C）环境。在整个试验过程中，相对湿度保持恒定（50% ± 5%）。所有数据均使用 R 和 GraphPad 软件中的单向方差分析进行分析，P < 0.05，并以平均值±SEM 表示。与其他组相比，热应激使 CHS 和 TMHS 组的最终体重和 ADG 显着降低（P < 0.05）。Embryonic TM 显着增加（P < 0.05）热休克蛋白相关基因（HSP70、HSP90 和 HSPH1）和抗氧化相关基因（GPX1 和 TXN）的表达。与 CHS 鸡相比，TMHS 鸡的盲肠挥发性脂肪酸 (VFA) 浓度显着增加 (P < 0.05)。盲肠微生物分析显示，TMHSS 组的 α 和 β 多样性以及粪球菌显着富集（P < 0.05）。在热应激禽类中补充孵化前 TM 和孵化后黄芩素可减轻热应激对鸡生长性能的不利影响，上调有利基因表达，增加 VFA 产量，并通过增加有益微生物群落促进肠道健康。