De Basilio V, Requena F, León A, Vilariño M, Picard M
Universidad Central De Venezuela, Facultad de Agronomia, Apdo. 4579, Maracay, Venezuela.
Poult Sci. 2003 Aug;82(8):1235-41. doi: 10.1093/ps/82.8.1235.
Early age thermal conditioning (TC) durably improves resistance of broilers to heat stress and reduces body temperature (Tb). Three experiments on broiler chicks were conducted to evaluate the effects of TC at 5 d of age on Tb variation measured by thermometer between 4 and 7 d of age, under a tropical environment. Because manipulation of chickens to measure Tb with a thermometer may increase Tb, a preliminary experiment on 13 3-to-4-wk-old male broilers compared Tb measured by telemetry to Tb measured in the terminal colon during three successive periods at 22, 33, and 22 degrees C. During heat exposure, Tb rapidly increased by 0.9 degrees C and plateaued over 24 h. During the last period, seven of the broilers rapidly reduced Tb to a plateau lower than the initial Tb, although six broilers exhibited more variable Tb. Measurement by thermometer underestimated on average core Tb by 0.28 degrees C at 22 degrees C and by 0.57 degrees C at 33 degrees C, whereas Tb recorded by telemetry was not affected by manipulation of the chickens. TC reduced Tb 24 h later in the three experiments. Compared to unexposed control chicks (N), 12 h of TC at 40 degrees C did not significantly reduce Tb at 7 d of age, although 24 h did. TC at 38 and 40 degrees C over 24 h significantly reduced Tb variation from 4 to 7 d of age compared to N chicks, whereas 36 degrees C did not. Withdrawing feed from the chicks for 2 h prior to measurement did not significantly reduce Tb at 4 and 7 d of age, but Tb reduction due to TC was greater in fed chicks (0.28 degrees C) than in chicks without feed (0.05 degrees C). Early age thermal conditioning at 38 to 40 degrees C at 5 d of age for 24 h reduced body temperature of 7-d-old male broilers.
早期热调节（TC）可持久提高肉鸡对热应激的抵抗力并降低体温（Tb）。进行了三项关于肉鸡雏鸡的实验，以评估5日龄时的热调节对热带环境下4至7日龄用温度计测量的体温变化的影响。由于用温度计测量鸡的体温时对鸡的操作可能会使体温升高，因此对13只3至4周龄雄性肉鸡进行了一项初步实验，比较了遥测法测量的体温与在22、33和22摄氏度的三个连续时间段内终末结肠测量的体温。在热暴露期间，体温迅速升高0.9摄氏度，并在24小时内趋于平稳。在最后一个时间段内，7只肉鸡的体温迅速降至低于初始体温的平稳水平，尽管有6只肉鸡的体温变化更大。在22摄氏度时，温度计测量平均低估核心体温0.28摄氏度，在33摄氏度时低估0.57摄氏度，而遥测记录的体温不受对鸡的操作影响。在三项实验中，热调节在24小时后降低了体温。与未暴露的对照雏鸡（N）相比，40摄氏度下12小时的热调节在7日龄时并未显著降低体温，尽管24小时的热调节有此效果。与N雏鸡相比，38和40摄氏度下24小时的热调节显著降低了4至7日龄的体温变化，而36摄氏度则没有。在测量前2小时不给雏鸡喂食，在4和7日龄时并未显著降低体温，但热调节导致喂食雏鸡的体温降低幅度（0.28摄氏度）大于未喂食雏鸡（0.05摄氏度）。5日龄时在38至40摄氏度下进行24小时的早期热调节可降低7日龄雄性肉鸡的体温。
