Department of Ostrich, Special Domestic Animal Institute, Research Institute of Zabol, Zabol, Iran.
Department of Animal Science, Faculty of Agriculture and Natural Resources, Persian Gulf University, Bushehr, 75169, Iran.
J Therm Biol. 2024 Oct;125:103976. doi: 10.1016/j.jtherbio.2024.103976. Epub 2024 Sep 18.
The study investigated the effects of embryonic thermal manipulation (TM) and post-hatch guanidinoacetic acid (GAA) supplementation on male broiler chickens exposed to chronic heat stress (HS). Ross 308 eggs (n = 710) were randomly assigned to control (37.8 °C, 56% RH) or TM (39.5 °C, 65% RH for 12 h/day from embryonic day 7-16) treatments. After hatching, chicks were further assigned to four dietary treatments (n = 12 birds/pen, 5 replicates/treatment): control, control with 1.2 g/kg GAA supplementation (CS), TM, and TM with 1.2 g/kg GAA supplementation (TMS). All birds were subjected to chronic HS (32-36 °C and 55% RH for 6 h/day) from day 28-42. Embryonic TM treatment decreased hatchability, hatching weight (HW), and facial temperature (FT). During the pre-HS period (days 1-28), no significant differences in feed conversion ratio (FCR) and mortality were observed, although the TM group exhibited the lowest body weight gain (BWG). Following HS exposure (days 29-42), the TMS group displayed significantly higher BWG than the control and CS groups. The TM and TMS groups also demonstrated significantly lower FCR and mortality rates during this period. Across the entire period (days 1-42), BWG was significantly higher in the TMS group compared to other groups. Furthermore, TM and TMS treatments were associated with lower mortality rates, improved FCR, better European Performance Efficiency Index (EPEI), and reduced abdominal fat deposition. The experimental treatments did not significantly affect intestinal morphology or most blood parameters, except triiodothyronine (T3), thyroxine (T4), and uric acid. Plasma concentrations of T3, T4, and uric acid were significantly lower in the TM and TMS groups compared to the control and CS treatments. The findings suggest that a combined strategy of embryonic TM and post-hatch dietary GAA supplementation may not only alleviate the detrimental effects of HS but also promote beneficial physiological responses in broiler chickens.
本研究旨在探讨胚胎期热处理（TM）和出壳后胍基乙酸（GAA）补充对暴露于慢性热应激（HS）的雄性肉鸡的影响。Ross 308 蛋（n=710）被随机分为对照组（37.8°C，56% RH）或 TM 组（胚胎期第 7-16 天每天 12 小时 39.5°C，65% RH）。出壳后，雏鸡进一步分为四个日粮处理组（每栏 12 只鸡，5 个重复/处理）：对照组、对照组添加 1.2g/kg GAA 日粮（CS）、TM 组和 TM 组添加 1.2g/kg GAA 日粮（TMS）。所有鸡从第 28-42 天接受慢性 HS（32-36°C，55% RH，每天 6 小时）。胚胎期 TM 处理降低了孵化率、孵化体重（HW）和面部温度（FT）。在 HS 前阶段（第 1-28 天），观察到饲料转化率（FCR）和死亡率没有显著差异，尽管 TM 组的体重增加（BWG）最低。暴露于 HS 后（第 29-42 天），TMS 组的 BWG 显著高于对照组和 CS 组。在这段时间里，TM 和 TMS 组的 FCR 和死亡率也显著降低。整个时期（第 1-42 天），TMS 组的 BWG 显著高于其他组。此外，TM 和 TMS 处理与较低的死亡率、改善的 FCR、更好的欧洲生产效率指数（EPEI）和减少腹部脂肪沉积有关。实验处理对肠道形态或大多数血液参数没有显著影响，除了三碘甲状腺原氨酸（T3）、甲状腺素（T4）和尿酸。与对照组和 CS 处理相比，TM 和 TMS 组血浆 T3、T4 和尿酸浓度显著降低。研究结果表明，胚胎 TM 与出壳后日粮 GAA 补充相结合的策略不仅可以减轻 HS 的不利影响，还可以促进肉鸡的有益生理反应。
