杨语嫣, 王雪洁, 张敏红, 冯京海^,中国农业科学院北京畜牧兽医研究所/动物营养学国家重点实验室,北京 100193

The Upper Limit Temperature of Thermoneutral Zone Estimated by the Changes of Temperature and Respiration Rate of the Broilers

YANG YuYan, WANG XueJie, ZHANG MinHong, FENG JingHai^,Institute of Animal Science, Chinese Academy of Agricultural Sciences/State Key Laboratory of Animal Nutrition, Beijing 100193

通讯作者: 冯京海,E-mail： fjh6289@126.com

收稿日期:2018-06-7接受日期:2018-12-19网络出版日期:2019-02-13

基金资助:

国家重点研究发展计划.2016YFD0500509 中国农业科学院科技创新工程.ASTIP-IAS07

Received:2018-06-7Accepted:2018-12-19Online:2019-02-13
作者简介 About authors
杨语嫣,E-mail：279894273@qq.com。






摘要
目的 通过非线性分段回归模型,分析随环境温度逐渐升高,肉鸡体表、体核温度和呼吸频率开始升高时的环境温度,即拐点温度（IPT）,估测肉鸡热中性区、热舒适区的上限温度。方法 试验选择21日龄AA肉鸡10只,饲养于人工环境控制舱内。舱内温度由18℃开始,每0.5 h升高1℃,至33℃维持0.5 h后,逐渐降至20℃,循环3 d。利用微型温度记录仪连续监测肉鸡体表和体核温度（每10min记录1次）。结果 经非线性分段回归分析,3次（天）估测出的肉鸡体表温度的拐点温度（IPT_ST）分别为21.18、21.09、21.13℃,平均21.13℃。肉鸡IPT_ST个体之间的变异较大,3次测定的变异系数分别为6.31、6.15、5.64;而同一只肉鸡3次估测的IPT_ST差别较小,10只鸡的变异系数平均为0.52,表明这种估测IPT_ST的方法重复性较好。肉鸡体核温度的拐点温度（IPT_CT）3次测定的结果分别为27.80、27.98、27.67℃,平均27.82℃。个体之间IPT_CT的变异系数为2.82、2.75、2.78,而同只肉鸡3次估测的IPT_CT变异较小,平均变异系数为0.90,表明这种估测IPT_CT的方法重复性较好。肉鸡呼吸频率的拐点温度（IPT_RR）3次测定的结果分别为28.42、29.52、29.25℃,平均29.06℃。由于肉鸡在高温环境下喘息并非持续发生,本试验呼吸频率的测定时间过短（每个温度下每只鸡测定了1 min）,造成部分肉鸡测定的呼吸频率过低,导致估测的IPT_RR偏高。结论 根据热中性区的定义,3—4周龄肉鸡热舒适区上限温度即为IPT_ST（21.13℃）,而热中性区上限温度应低于IPT_CT（27.82℃）。
关键词： 肉鸡;体温;呼吸频率;拐点温度;连续升温

Abstract
【Objective】 The present study was conducted to measure the variations of surface temperature (ST), core temperature (CT) and respiratory rate (RR) of broilers with increasing ambient temperature (AT), and analyze these data with a broken-line model to determine the inflection point temperature (IPT, the certain AT above which the body temperature or RR of the broilers started to change). 【Method】 Ten AA broilers (21 days old) were raised in one controlled climate chamber. The AT of chamber was increased gradually by one degree per 0.5 h from 18℃ to 33℃, and then gradually decreased to 20℃. The CT and ST of broilers, as well as the AT in the chamber were recorded at 10 min intervals using mini temperature data loggers. The experiment was repeated three times on three days. 【Result】 The IPT based on ST (IPT_ST) for three consecutive days were 21.18, 21.09 and 21.13℃, average 21.13℃. The variation coefficients of IPT_ST between individual broilers was 6.13, 6.15 and 5.64 for three measurements, the variation coefficient of IPT_ST between three measurements was 0.52% on average, indicating that the method of estimating IPT_ST was better repeatable. The IPT based on CT (IPT_CT) for three consecutive days were 27.80, 27.98 and 27.67℃, with an average of 27.82℃. The variation coefficients of IPT_CT between individual broilers was 2.82, 2.75, 2.78 for three measurements, the variation coefficient of IPT_ST between three measurements was 0.90% on average, indicating that the method of estimating IPT_CT was better repeatable. The IPT based on RR (IPT_RR) for three consecutive days were 28.42, 29.52 and 29.25℃, with an average of 29.06℃. Since the panting of broilers is intermittent, the respiratory of broilers under high temperature maybe normal during the period of RR measurement (only 1 min per chick), which maybe result in an under-estimated the RR, and an over-estimated IPT_RR of some broilers. 【Conclusion】 According to the definition of the thermal neutral zone, the upper limit temperature of the thermal neutral zone of 3-4 weeks old broilers should be lower than IPT_CT (27.82℃), and the upper limit temperature of thermal comfort zone is IPT_ST (21.13℃).
Keywords：broilers chicken;body temperature;respiratory rate;inflection point temperature;increasing ambient temperature


PDF (499KB)元数据多维度评价相关文章导出EndNote|Ris|Bibtex收藏本文
本文引用格式
杨语嫣, 王雪洁, 张敏红, 冯京海. 升温环境下肉鸡体温和呼吸频率对热中性区上限温度估测[J]. 中国农业科学, 2019, 52(3): 550-557 doi:10.3864/j.issn.0578-1752.2019.03.015
YANG YuYan, WANG XueJie, ZHANG MinHong, FENG JingHai. The Upper Limit Temperature of Thermoneutral Zone Estimated by the Changes of Temperature and Respiration Rate of the Broilers[J]. Scientia Agricultura Sinica, 2019, 52(3): 550-557 doi:10.3864/j.issn.0578-1752.2019.03.015

0 引言

【研究意义】MOUNT^[1]将热中性区（thermoneutral zone,TNZ）定义为,动物维持体温所需的能量最低且恒定的环境温度范围。家畜环境卫生学将TNZ定义为恒温动物依靠物理和行为调节即可维持体温正常的环境温度范围^[2]。从TNZ的定义可以看出,动物在热中性区内最为舒适,能量用于生产的效率最高。因此研究动物的热中性区,通过环控设备将畜舍温度维持在热中性区内,不仅有利于动物生产,还符合动物的福利需求。【前人研究进展】一般通过测定家禽产热量的变化估测家禽热中性区^[3-6] 。测定家禽产热量需要呼吸舱等试验设备,方法较为复杂。VAN ES等^[3] 发现,家禽的产热量随环境温度升高持续降低,并没有出现理论上的恒定且最低的区域,这主要是由于随环境温度升高,家禽可以通过减少采食量,降低产热量来维持体温的恒定。另外不同体重或不同日龄的家禽热中性区也不同^[6],家禽测试之前的适应温度对家禽的热中性区的影响也很大。ARIELI等^[7] 发现,试验前蛋鸡舍内平均温度降低10℃将导致蛋鸡热中性区下限温度降低8.5℃,上限温度降低3℃。由此可见,在某一特定条件下测定的家禽热中性区很可能并不适用于不同日龄、不同采食水平,不同环境温度下的所有家禽,因此需要发展一种可以快速、简便的,适用于各种生产条件下估测家禽热中性区的方法。【本研究切入点】ARIELI等^[7] 将呼吸频率超过60次/min时的环境温度定为上限温度,这种方法主要依据经验判断,缺乏科学依据。HUYNH等^[8] 通过测定不同温度下育肥猪体温、呼吸频率、产热量等指标的变化,利用非线性分段回归的方法,分析了这些指标开始发生剧烈变化时的环境温度,即拐点温度（IPT）。【拟解决的关键问题】监测连续升高环境温度下,肉鸡体温和呼吸频率的变化,通过分析各指标开始变化时的拐点温度,估测肉鸡热中性区的上限温度,并探讨这种方法的可重复性。

1 材料与方法

1.1 试验动物及管理

选择18日龄健康AA肉鸡10只,饲养于动物营养学国家重点实验室环控舱内,使用单层平养笼具。日常饲养管理参照《AA肉鸡饲养管理手册,2009》进行。试验期间自由采食与饮水,采用玉米-豆粕型饲粮,参照NRC（1994）^[9] 营养需要配制。

1.2 环控舱温度设置

适应期（18—20日龄）环控舱内温度维持在（20±1）℃,相对湿度维持在（60±10）%。试验期（21—23日龄）每天上午10：00逐渐将环境温度由20℃降低至18℃,从11：00开始,每半个小时升温1℃,直至18：30升温到33℃并维持0.5 h,然后逐渐恢复到20℃;第2、3天按照相同程序设置环境温度。相对湿度始终维持60%不变,具体温度设置见图1。

图1

新窗口打开|下载原图ZIP|生成PPT
图1试验期间的环境温度的设置

Fig. 1Temperature setting during the experiment

1.3 体温及呼吸频率的测定

环控舱内温度：将微型温度记录仪（DS1922L,Maxim,San Jose,CA,U.S.）放置于肉鸡相同高度,每10 min测定一次,实时记录舱内温度变化。

通过控制电脑设定环控舱的最低温度为18℃,环控舱根据温度探头感受到的温度进行自动调节,环控舱标识的控温精度为±1℃,但有可能会超过±1℃,也就是说设定18℃,环境温度可能会在16.5—19.5℃范围内变化。而微型温度记录仪放置于肉鸡相同高度,每10 min测定一次环境温度,微型温度记录仪放置的位置与环控舱温度探头并不在相同位置,2个仪器之间会有差异,因此温度记录仪实时记录的舱内温度存在部分15℃多的现象。

体表温度（ST）：参考常玉等^[10] 的方法,使用微型温度记录仪测定肉鸡背部皮肤温度。在适应期第一天,剪除所测肉鸡背部正中5 cm²的羽毛,将微型温度记录仪绑缚在肉鸡背部,使记录仪上传感器一面紧密贴合在肉鸡背部皮肤上。由于绷带的阻隔,避免环境热源通过辐射、对流的方式直接干扰体表温度的测定。

体核温度（CT）：参考常玉等^[10] 的方法,使用微型温度记录仪测定。

温度记录仪在适应期绑定或投喂,预先设定好开始时间为试验开始当天的08：00,记录频率为每10 min记录一次,连续记录72 h后,取出温度记录仪导出数据进行分析。温度记录仪使用前利用北京市海淀区计量检测所校正过的标准水银温度计进行校正,校正方法参考PURSWELL等^[11]的操作方法。

呼吸频率（RR）：使用秒表和计数器,由专人记录肉鸡每分钟的呼吸次数。每30 min观察一次,每只鸡每次连续计数1 min。

试验结束后发现部分肉鸡呼吸频率的数据不符合折线回归的趋势。经仔细观察发现,肉鸡在高温环境下的喘息并非持续发生,喘息一段时间后呼吸频率恢复正常,休息一段时间后继续喘息。本次研究每只肉鸡每个环境温度下仅记录1 min内的呼吸次数,如果计数时该肉鸡处于正常呼吸状态,则该鸡的呼吸频率明显偏低,导致部分肉鸡的数据出现异常。根据前人研究的结果,当环境温度超过30℃时,肉鸡的呼吸频率应超过50次/min。本研究将30—33℃ 4个温度点的呼吸频率进行筛选,如果只有一个温度点的呼吸频率低于50次/min,则将该数据做缺失处理,如果有2个或2个以上温度点的数据均低于50次/min,则该只肉鸡数据不进行分析。

1.4 数据统计与分析

参考HUYNH等^[8]的方法,采用spss 17.0统计软件中非线性分段回归分析（Nonliner regression）,对连续升温下肉鸡体表、体核温度和呼吸频率数据进行分段回归分析。分段回归模型为：

当 T ≥ IPT 时：Y = C + Z × (AT- IPT)

当 T < IPT 时：Y = C

其中,Y是指体温及呼吸频率;C是指肉鸡体温调节指标未发生变化时的常数;Z是指肉鸡体温调节指标发生变化时的斜率;T是指环境温度;IPT是指肉鸡体温调节指标开始发生变化时所对应的环境温度点。

2 结果

2.1 肉鸡体表温度的变化估测的拐点温度及变异

由图2可见,环境温度由18℃升高至33℃的过程中,在低于某一温度时,肉鸡的体表温度变化不大,处于稳定状态;当超过这一温度时,肉鸡的体表温度开始呈线性上升趋势。经过非线性分段回归分析,可以计算出肉鸡体表温度开始升高时的环境温度,即肉鸡体表温度的拐点温度（IPTst）。

第1天计算出的平均IPTst为21.18℃（图2-a）,当环境温度低于21.18℃时,ST=33.14℃;当环境温度超过21.18℃时：ST=33.14+0.36×（环境温度-21.18）。第2天的平均IPTst为21.09℃（图2-b）;第3天为21.13℃（图2-c）,3 d平均为21.13℃。

图2

新窗口打开|下载原图ZIP|生成PPT
图2连续升温环境下肉鸡体表温度开始升高时的环境温度（拐点温度,IPT_ST）及其变异

a：第1天测试;b：第2天测试;c：第3天测试;d：个体之间和3 d测试结果之间的变异
Fig. 2The inflection point temperature (IPT_ST, which is the certain ambient temperature above which the surface temperature of broilers started to change)

at first day (a), second day (b), and third day (c) and its variation between individuals or three days (d)


利用本方法计算出的IPTst个体之间存在较大变异（图2-d）,变异系数分别为6.31（第1天）、6.15（第2天）和5.64（第3天）;但是同一只鸡连续测定3次的变异系数相对较小,分别为1.06、0.67、0.14、0.05、0.68、0.59、0.76、0.75、0.01、0.52,平均0.52。

2.2 肉鸡体核温度变化估测的拐点温度及变异

由图3可见,环境温度由18℃升高至33℃的过程中,在低于某一温度时,肉鸡的体核温度变化不大,处于稳定状态;当超过这一温度时,肉鸡的体核温度开始呈线性上升趋势。经过非线性分段回归分析,可以计算出肉鸡体核温度开始升高时的环境温度,即肉鸡体核温度的拐点温度（IPT_CT）。

图3

新窗口打开|下载原图ZIP|生成PPT
图3连续升温环境下肉鸡体核温度开始升高时的环境温度（拐点温度,IPT_CT）及其变异

a：第1天测试;b：第2天测试;c：第3天测试;d：个体之间和3 d测试结果之间的变异。2只鸡体内芯片损坏,无数据。分别为1-4和1-8
Fig. 3The inflection point temperature (IPT_CT, which is the certain ambient temperature above which the core temperature of broilers started to change)

at first day (a), second day (b), and third day (c) and its variation between individuals or three days (d). The loggers inside 2 chickens were damaged, so the data of 1-4 and 1-8 were missing


第1天计算出的平均IPT_CT为27.80℃（图3-a）,当环境温度低于27.80℃时：ST=39.76℃;当环境温度超过27.80℃时：ST=39.76+0.24×（环境温度-27.80）。第2天的平均IPT_CT为27.98℃（图3-b）;第3天为27.67℃（图3-c）,3 d平均为27.82℃。

利用本方法计算出的IPT_CT个体之间存在较大变异（图3-d）。8只鸡（有2只鸡体内芯片损坏）之间的个体变异系数分别为2.82（第1天）、2.75（第2天）和2.78（第3天）;但是同一只鸡连续测定3次的变异系数相对较小,分别为1.42、1.43、0.92、1.30、0.85、0.77、0.01、和0.51,平均0.90。

2.3 基于升温环境下肉鸡呼吸频率的变化估测的拐点温度及变异

由于高温环境下肉鸡热喘息的现象并非持续发生,而本试验测定肉鸡呼吸频率的时间过短,导致部分肉鸡高温时呼吸频率的数据出现异常。剔除不合理数据后,第1天剩余8只鸡,折线回归分析得出,平均IPT_RR为28.42℃（图4-a）,当环境温度低于28.42℃时：RR=40.65次/min;当环境温度超过28.42℃时：RR=40.65+9.03×（环境温度-28.42）。第2天仅剩余1只鸡的数据,IPT_RR为29.52℃（图4-b）;第3天剩余5只鸡的数据,计算出的平均IPT_RR为29.25℃（图4-c）。

由图4-d可以看出,利用本方法计算出的IPTst个体之间存在较大变异。由于部分肉鸡数据异常,无法计算3 d估测值的变异。

图4

新窗口打开|下载原图ZIP|生成PPT
图4连续升温环境下肉鸡呼吸频率开始升高时的环境温度（拐点温度,IPT_RR）及其变异

a：第1天测试;b：第2天测试;c：第3天测试;d：个体之间和3 d测试结果之间的变异。筛除不合理数据后,第1天剩8只鸡的数据,第2天剩1只鸡的数据,第3天剩5只鸡的数据
Fig. 4The inflection point temperature (IPT_RR, which is the certain ambient temperature above which the respiratory rate of broilers started to change)

At first day (a), second day (b), and third day (c) and its variation between individuals or three days (d). The data of 8 chickens at the first day, 1 chicken at the second day, and 5 chickens at the third day were left after screening out the unreasonable data

3 讨论

当环境温度变化时,家禽可以通过血管的收缩或舒张,改变体表的血流量,调节体表温度^[12,13]。高温环境下家禽体表温度升高^[14-16] 。MALHEIROS 等^[17] 研究了20、25和35℃环境下肉鸡体表温度的变化,发现肉鸡体表温度随环境温度升高呈线性升高。NASCIMENTO 等^[18]也发现,在18、25和32℃下,肉鸡体表温度也随环境温度升高呈线性升高。上述研究设置的环境温度点仅为3个,无法进行精确的分段回归分析,只能大致得出体表温度的线性变化。本研究从18—33℃一共设定了16个温度点,每个温度点测定了3次,利用非线性分段回归的方法,可以准确估测出肉鸡体表温度开始升高时的拐点温度。另外虽然个体之间IPTst的变异较大,但同一只鸡测定三次,IPTst的变异较小,这表明采用微型芯片测定连续升温环境下肉鸡的体表温度,分析计算IPTst的方法重复性较好,但需要尽可能多的样品数量才能准确反映整个鸡群的IPTst。

家禽体表覆盖有羽毛,当环境温度超过热中性区后,主要通过加快呼吸频率（热喘息）,增加蒸发散热量^[19]。大量研究均证明高温下肉鸡的呼吸频率显著升高^[20,21,22],这些研究往往是2个或3个温度点之间的比较,缺乏连续升高温度下呼吸频率的变化数据。肉鸡在高温环境下的热喘息并非持续发生,一般是喘息一段时间休息一段时间。随温度升高,喘息时间越长,休息时间越短,且喘息时的呼吸频率越高。本试验每只鸡呼吸频率的测定时间仅1 min,如果测定时正处于或部分处于肉鸡的休息时间,将导致该温度下肉鸡呼吸频率的数据明显偏低。因此本文将部分异常数据进行了缺失处理。从现有数据可以看出,随环境温度持续升高,肉鸡呼吸频率存在明显的拐点温度。但由于个别数据的异常,可能导致本次估测的拐点温度偏高。今后需要进一步研究不同高温对肉鸡热喘息持续时间、休息时间以及热喘息时呼吸频率的影响,通过延长记录时间或仅记录喘息时的呼吸频率,探寻合理的呼吸频率记录方法,应用本试验的非线性分段回归分析,才能准确估测出肉鸡呼吸频率的拐点温度。

当环境温度持续升高,肉鸡通过减少产热、增加可感散热和蒸发散热仍无法到达平衡时,会导致体核温度（或直肠温度）显著升高。与20—22℃相比,32—37℃高温环境下肉鸡的体核温度显著升高,但25—27℃环境下肉鸡体核温度并未有显著变化^[23-27] 。由于大部分研究设定的环境温度点较少,未进行非线性分段回归分析。本研究设定了16个温度点,每个温度点测定了3次,利用非线性分段回归的方法,可以准确估测出肉鸡体核温度开始升高时的拐点温度。另外,虽然个体之间IPT_CT的变异较大,但同一只鸡测定3次,IPT_CT的变异较小,这表明采用微型芯片测定连续升温环境下肉鸡的体核温度,分析计算IPT_CT的方法重复性较好,但需要尽可能多的样品数量才能准确反映整个鸡群的IPT_CT。

国际生理学联合会热委员会（IUPS）将热中性定义为：动物仅通过可感散热的调节,无需改变代谢产热或蒸发散热即可维持体温正常的环境温度范围^[28] 。可感散热是指动物通过传导、对流和辐射进行散热,这种散热方式主要通过改变体表温度进行调节。在热中性区内动物仅通过改变体表温度即可维持正常体温^[29-31] 。根据IUPS的定义,在热中性区内部包含一个热舒适区,其上限温度应该为体表温度的拐点温度。当环境温度处于热舒适区内,肉鸡不需要通过改变体表温度即可维持体温恒定;当环境温度逐渐升高,超过热舒适区时,肉鸡通过提高体表温度即可维持体温恒定（此时依然处于热中性区内）;当环境温度继续升高,超出热中性区后,肉鸡必须通过增加蒸发散热维持体温恒定。因此蒸发散热开始增加时的环境温度（即肉鸡呼吸频率的拐点温度）可以定为肉鸡热中性区的上限温度。然而由于本试验呼吸频率测定时间过短,导致部分数据偏低,因此通过非线性回归分析得出呼吸频率开始升高时的拐点温度偏高,无法准确估测出肉鸡热中性区的上限温度。如果环境温度仍持续升高,肉鸡的散热量不能抵消自身的产热量时,肉鸡体核温度开始升高,因此理论上肉鸡体核温度的拐点温度应该高于呼吸频率的拐点温度。然而本研究测定的IPT_ST为21.13℃,IPT_RR为29.06℃,IPT_CT为27.82℃,IPT_CT反而低于IPT_RR。推测是由于本试验关键温度点记录的呼吸频率偏低,导致估测的拐点温度后移,数值偏高。GILOH等发现在急性热应激期间,肉鸡的体表温度与体核温度存在很强的正相关关系,可以替代体核温度,作为反映肉鸡热应激的指标^[32]。但这只能在肉鸡处于急性热应激的状态,此时环境温度远超过肉鸡热中性区之后。

4 结论

随环境温度升高,肉鸡体表温度和体核温度开始升高时的环境温度（拐点温度）分别为21.13℃和27.82℃。连续测定3次,同一肉鸡体表温度和体核温度的拐点温度变异较小,表明这一方法具有较好的可重复性。呼吸频率由于测定时间过短,数据异常,无法得出准确的拐点温度。根据热中性区的定义,3—4周龄肉鸡热舒适区上限温度为21.13℃,热中性区上限温度低于27.82℃。

参考文献 View Option 原文顺序
文献年度倒序
文中引用次数倒序
被引期刊影响因子

[1] MOUNT L E . The concept of thermal neutrality//Heat Loss from Animals and Man
London: Easter School in Agricultural Science, 1974: 425-439.
[本文引用: 1]

[2] 李如志, 颜培实 . 家畜环境卫生学. 4版 . 北京: 中国高等教育出版社, 2011: 39-41.
[本文引用: 1]

LI R Z, YAN P S. Domestic Animals and Environmental Hygiene. 4th ed. Beijing: Higher Education Press, 2011: 39-41. (in Chinese)
[本文引用: 1]

[3] VAN ES A J, Van A D, NIJKAMP H J, VOGT J E, SCHEELE C W . Thermoneutral zone of laying hens kept in batteries
Journal of Animal Physiology and Animal Nutrition, 1973,32(1/5):121-129.
DOI:10.1111/j.1439-0396.1973.tb00374.xURL [本文引用: 2]
http://doi.wiley.com/10.1111/j.1439-0396.1973.tb00374.x

[4] VAN KAMPEN M, MITCHELL B W, SIEGEL H S . The rmoneutral zone of chickens as determined by measuring heat production, respiration rate, and electromyographic and electroencephalographic activity in light and dark environments and changing environmental temperatures
The Journal of Agricultural Science, 1979, 92(1):219-226.
DOI:10.1017/S0021859600060664URL
Electromyographic (EMG) activity, electroencephalographic (EEG) activity, heat production (H), respiration rate (RR), and body temperature (TB) of unacclimatized chickens were measured during periods of light and darkness at ambient temperatures (Ta) between 7·7 and 37·7 °C. The difference between pectoral muscle and abdomen temperature was less than 0·1 °C over the entire temperature range. Body temperature increased (P ≤ O·l) when Tawas above 27·5 °C and was higher in the light than in the dark (P ≤ 0·05). Respiration rate decreased significantly with increasing Ta. The decrease, however, was not as great during the dark (P ≤ 0·05) as during the light period (P s05 001). Heat production decreased (P ≤ 0·01) with increasingTaup toTa= 22·3 °C. There was no significant difference between heat production during the light period and that during the dark period. EMG amplitude declined (P ≤ 0·01) with increasingTaup to 27·5 °C in the light and 22·3 °C in the dark and was higher (P ≤ 0·05) in the light than in the dark. Mean frequency of EMG activity was independent of light andTa. The percentage of low-frequency EEG activity in the dark did not change significantly over the entireTarange, but in the light it decreased asTaincreased above 25·7 °C (P ≤ 0·05). The percentage of high-frequency EEG activity appeared as a mirror image of low-frequency activity. Overall results indicated a thermoneutral zone between 32·2 and 37·7 °C in the light and between 27·5 and 37·7 °C in the dark.

[5] MELTZER A, GOODMAN G, FISTOOL J . Thermoneutral zone and resting metabolic rate of growing White Leghorn type chicks
. British Poultry Science, 1982, 23(5):383-391.
DOI:10.1080/00071688208447972URLPMID:7139388
1. Metabolic rate was determined once a week in pullets from commercial flocks of the local White Leghorn strain from the age of 1 d to 13 weeks.

[6] MELTZER A . Thermoneutral zone and resting metabolic rate of broilers
. British Poultry Science, 1983, 24(4):471-476.
DOI:10.1080/00071668308416763URLPMID:6667388 [本文引用: 2]
1. Metabolic rate was determined once a week in broilers from a commercial source, from 1 to 63 d of age.

[7] ARIELI A, MELTZER A, BERMAN A . The thermoneutral temperature zone and seasonal acclimatization in the hen
British Poultry Science, 1980,21(6):471-478.
[本文引用: 2]

[8] HUYNH T T T, AARNINK A J A, VERSTEGEN M W A, GERRITS W J J, HEETKAMP M J W, KEMP B, CANH T T . Effects of increasing temperatures on physiological changes in pigs at different relative humidities
Journal of Animal Science, 2005,83(6):1385-1396.
DOI:10.2527/2005.8361385xURLPMID:15890816 [本文引用: 2]
Abstract The effects of relative humidity (RH) and high ambient temperature (T) on physiological responses and animal performance were studied using 12 groups (10 gilts per group) in pens inside respiration chambers. The microclimate in the chamber was programmed so that T remained constant within a day. Each day, the T was increased by 2 degrees C from low (16 degrees C) to high (32 degrees C). Relative humidity was kept constant at 50, 65, or 80%. The pigs' average initial BW was 61.7 kg (58.0 to 65.5 kg), and their average ending BW was 70.2 kg (65.9 to 74.7 kg). Respiration rate (RR), evaporative water (EW), rectal temperature (RT), skin temperature (ST), voluntary feed intake (VFI), water-to-feed ratio (rW:F), heat production (HP), and ADG were analyzed. The animals had free access to feed and water. We determined the T above which certain animal variables started to change: the so-called inflection point temperature (IPt) or "upper critical temperature." The first indicator of reaction, RR, was in the range from 21.3 to 23.4 degrees C. Rectal temperature was a delayed indicator of heat stress tolerance, with IPt values ranging from 24.6 to 27.1 degrees C. For both these indicators the IPt was least at 80% RH (P < 0.05). Heat production and VFI were decreased above IPt of 22.9 and 25.5 degrees C, respectively (P < 0.001). For each degree Celsius above IPt, the VFI was decreased by 81, 99, and 106 g/(pig.d) in treatments 50, 65, and 80% RH, respectively. The ADG was greatest at 50% RH (P < 0.05). Ambient temperature strongly affects the pigs' physiological changes and performance, whereas RH has a relatively minor effect on heat stress in growing pigs; however, the combination of high T and high RH lowered the ADG in pigs. The upper critical temperature can be considered to be the IPt above which VFI decreased and RT then increased. Temperatures of the magnitude of both these IPt are regularly measured in commercial pig houses. We conclude that the upper critical temperatures for 60-kg, group-housed pigs fed ad libitum are between 21.3 and 22.4 degrees C for RR, between 22.9 and 25.5 degrees C for HP and VFI, and between 24.6 and 27.1 degrees C for RT. It is clear that different physiological and productive measurements of group-housed, growing-finishing pigs have different critical temperatures.

[9] National Research Council. Nutrition Requirements of Poultry, 9th ed Revised. Washington D.C.: National Academy Press, 1994.
[本文引用: 1]

[10] 常玉, 张少帅, 彭骞骞, 张敏红, 周莹, 夏九龙, 刁华杰, 冯京海 . 产蛋及喂料行为对蛋鸡体核和体表温度的影响
畜牧兽医学报, 2016,47(10):2045-2051.
[本文引用: 2]

CHANG Y, ZHANG S S, PENG Q Q, ZHANG M H, ZHOU Y, XIA J L, DIAO H J, FENG J H . Effects of egg laying and feeding behavior on the core and body temperature of the egg
Journal of Animal Husbandry and Veterinary Medicine, 2016,47(10):2045-2051. (in Chinese)
[本文引用: 2]

[11] PURSWELL J L, DOZIER W A, OLANREWAJU H A, DAVIS J D, XIN H, GATES R S . Effect of temperature-humidity index on live performance in broiler chickens grown from 49 to 63 days of age//9th International Livestock Environment Symposium. Valencia,
Spain, 2012,7:8-12.
DOI:10.13031/2013.41619URL [本文引用: 1]
The thermal environment in poultry housing is a primary influence on production efficiency and live performance. Heavy broilers (body weight > 3.2 kg) typically require high ventilation rates to maintain thermal comfort and production efficiency. However, large birds are observed to pant in mild to moderate thermal conditions, indicating that upper critical temperatures may be lower at larger body weights. Thermal comfort indices such as the temperature-humidity index (THI) integrate the effects of temperature and humidity and may offer a means to predict the effects of thermal conditions on performance. The objective of this study was to determine live performance of heavy broilers over a range of dry-bulb temperature (15°C, 21°C, and 27°C) and relative humidity (50%, 65%, and 80%), hence THI (14.8°C to 26.9°C). A series of four studies were completed with broiler chickens housed in environmental chambers. Live performance parameters including body weight, body weight gain, feed intake, and feed conversion ratio were compared; body temperature was measured in three birds of each treatment during one study. Results show that as THI exceeds approximately 21°C, bird performance significantly declined and body temperature increased up to 1.7°C above nominal body temperature for broilers (41°C). Regression analysis showed that a quadratic relationship exists between THI and the four performance parameters of interest. Prediction accuracy was decreased due to variability in the data and suggests data at additional THI points are necessary.

[12] WOLFENSON D, FREI Y F, SNAPIR N, BERMAN A . Heat stress effects on capillary blood flow and its redistribution in the laying hen
Pflugers Archiv European Journal of Physiology, 1981,390(1):86-93.
DOI:10.1007/BF00582717URLPMID:7195555 [本文引用: 1]
The effect of heat stress on capillary blood flow (CBF) distribution was examined in laying hens, using 15 micron microspheres, by determining CBF before and after elevating body temperature by 1-2 degrees C. No changes was evident in unfeathered metatarsal skin, although its temperature increased by 7 degrees C. Breast skin CBF change was 3.5 times larger than that of back skin. Comb CBF increase was larger than in wattles. CBF in upper respiratory tract increased proportionally to increment in respiratory frequency. Digestive system CBF was reduced by hyperthermia: the effect was pronounced in its upper organs (46% of normal) and decreased along the tract. CBF increased 4-fold in an expiratory abdominal muscle, a smaller rise occurred in a pectoral muscle and no change in a leg muscle. CBF in the tibia fell to 64% of normal. In the reproductive system, CBF fell to 58% of control level in the uterus, to 70-80% in the larger ovarian follicles and infundibulum with no significant changes in magnum and isthmus. Cerebral CBF increased during hyperthermia. Heat stress significantly reduced CBF to inner body organs, with marked differences between systems as well as within systems. Changes were more pronounced on 2 degrees C hyperthermia than on 1 degree C hyperthermia.

[13] WOLFENSON D . The effect of acclimatization on blood flow and its distribution in normothermic and hyperthermic domestic fowl
Comparative Biochemistry and Physiology. A, Comparative Physiology, 1986,85(4):739-742.
DOI:10.1016/0300-9629(86)90287-2URLPMID:2879677 [本文引用: 1]
1. 1. Blood flow and its distribution was examined in summer and winter acclimatized normothermic and hyperthermic domestic hens. 2. 2. A clear trend of season on normothermic blood flow distribution was not noted; however, a significant tendency towards increased flow in summer was recorded. 3. 3. In 22 out of 28 organs or tissues examined, blood flow was lower in winter than in summer: pectoral muscle, adrenal and jejunum winter to summer ratios were 36, 64 and 76%, respectively ( P < 0.05). 4. 4. During hyperthermia, blood flow to visceral organ decreased in both groups; in summer this reduction was less severe in parts of the digestive system and more pronounced in parts of the reproductive system.

[14] YAHAV S, LUGER D, CAHANER A, DOTAN M, RUSAL M, HURWITZ S . Thermoregulation in naked neck chickens subjected to different ambient temperatures
British Poultry Science, 1998,39:133-138.
DOI:10.1080/00071669889510URLPMID:9568311 [本文引用: 1]
1. Heterozygous (Na/na) naked neck chickens and their normally feathered (na/na) sibs, were exposed to constant ambient temperatures (Ta) ranging between 15 and 35C and 12h: 12h diurnal high:low temperatures of 15C:35C. 2. No significant effect of genotype was obtained in weight gain and food intake. However, the naked neck birds tended to gain somewhat more weight at high Ta and consume more food at low Ta. 3. At 35C Na birds showed better regulation of body temperature (Tb) and demonstrated considerably higher radiation from the neck. 4. The greater food intake of the naked neck chickens at 15C was associated with significantly higher packed cell volume, haemoglobin concentration, heart and liver size. These appear to involve both higher heat production and haemodynamic changes to accommodate the higher oxygen demands of the naked neck chickens at low Ta. 5. The results indicate the ability of the naked neck chickens, on the one hand to thermoregulate at low Tas and, on the other their slightly better capacity to maintain Tb at high Tas. However, no genotype advantage was obtained under diurnal cyclic temperature conditions.

[15] YAHAV S, RUSAL M, SHINDER D . The effect of ventilation on performance body and surface temperature of young turkeys
Poultry Science, 2008,87(1):133-137.
DOI:10.3382/ps.2007-00359URLPMID:18079462
Abstract Efficient ventilation affects thermoregulation and, thereby, the performance of domestic fowl. This became crucial as genetic selection for growth development significantly coupled with increased metabolic rate. The specific aims of this study were to elucidate a) the effects of different rates of ventilation on young turkey performance during exposure to constant 35, 30, and 25 degrees C and b) their effects on body temperature and surface temperature. In 3 separate experiments, turkeys were raised under regular conditions up to 3 wk of age. Thereafter, they were acclimated for 1 wk to the targeted ambient temperatures (T(a)) and to air velocities of 0.8, 1.5, 2.0, or 2.5 m/s and raised under those conditions up to 6 wk of age. Turkeys exposed to 35 degrees C performed optimally at an air velocity (AV) of 2 m/s; they exhibited significantly higher feed intake and significantly lower body temperature. At 30 degrees C, performance was optimal at AV of 1.5 to 2.5 m/s and significantly lower at 0.8 m/s. Performance of turkeys exposed to 25 degrees C did not vary with AV. Comparison of BW and feed intakes of turkeys exposed to the 3T(a) levels revealed significantly higher feed intake at 25 degrees C but similar BW compared with those exposed to 30 degrees C, meaning that those exposed to 25 degrees C used more energy for maintenance than for growth. In general, surface temperature of the body declined significantly with T(a), whereas that of the face and legs was significantly lower at 25 degrees C. It can be concluded that AV affects the performance of young turkeys. The range of AV within which BW was optimal expanded as T(a) declined. It can be further concluded that the combination of 30 degrees C with AV from 1.5 to 2.5 m/s was optimal for young turkeys.

[16] SOUZA J B F, ARRUDA A M V, DOMINGOS H G T, COSTA L L M . Regional differences in the surface temperature of naked neck laying hens in a semi-arid environment
International Journal Biometeorology, 2013, 57(3):377-380.
DOI:10.1007/s00484-014-0884-7URLPMID:22689146 [本文引用: 1]
The aim of this study was to evaluate the regional differences in the surface temperature of Naked Neck hens that were subjected to different temperatures in a semi-arid environment. The surface temperature was measured in four body regions (face, neck, legs and feathered area) of 60 Naked Neck hens. The following environmental variables were measured at the center of the shed: the black globe temperature ( T G ), air temperature ( T A ), wind speed ( U ) and relative humidity ( R H ). The T A was divided into three classes: 1 (24.0–26.002°C), 2 (26.1–28.902°C) and 3 (29.0–31.002°C). An analysis of variance was performed by the least squares method and a comparison of the means by the Tukey-Kramer test. The results showed a significant effect of T A class, the body region and the interaction between these two effects on the surface temperature. There was no significant difference between the T A classes for the face and neck. The legs and feathered area showed significant differences between the T A classes. Regarding the effect of body regions within each T A class, there was a significant difference among all regions in the three T A classes. In all T A classes the neck had the highest average followed by the face and legs. The feathered area showed the lowest average of the different T A classes. In conclusion, this study showed that there are regional differences in the surface temperature of Naked Neck hens, with the legs acting as thermal windows.

[17] MALHEIROS R D , MORAES V M B, BRUNO L D G, MALHEIROS E B, FURLAN R L, MACARI M . Environmental temperature and cloacal and surface temperatures of broiler chicks in first week Post-Hatch
Journal of Applied Poultry Research, 2000,9(1):111-117.
DOI:10.1093/japr/9.1.111URL [本文引用: 1]
Adequate environmental temperature during the brooding period is very important to future broiler performance. Thus, the objective of this study was to investigate the extent to which environmental temperature affects the body weight and cloacal and surface (back, head, wing, and shank) temperatures. The study also investigated the sensible heat loss by radiation of broiler chicks reared at thr...

[18] NASCIMENTO G R, NAAS I A, PEREIRA D F, BARACHO M S, GARCIA R . Assessment of broiler surface temperature variation when exposed to different air temperatures
Revista Brasileira De Ciência Avícola, 2011,13(4):259-263.
[本文引用: 1]

[19] HILLMAN P E, SCOTT N R, TIENHOVEN A V. Physiological responses and adaptations to hot and cold environments//Stress Physiology in Livestock. CRC Press, Inc, M. K. Yousef, ed. Boca Raton, FL. 1985: 27-28.
[本文引用: 1]

[20] TOYOMIZU, TOKUDA M M, MUJAHID A, AKIBA Y . Progressive alteration to core temperature, respiration and blood acid-base balance in broilers exposed to acute heat stress
The Journal of Poultry Science, 2005,42(2):110-118.
[本文引用: 1]

[21] ZHOU W T , YAMAMOTO . Effects of environmental temperature and heat production due to food intake on abdominal temperature, shank skin temperature and respiration rate of broilers
British Poultry Science, 1997,38(1):107-114.
DOI:10.1080/00071669708417949URLPMID:9088622 [本文引用: 1]
1. Eight broilers were used to determine the effects of environmental temperature and the increased heat production attributable to food intake on thermoregulatory physiological responses. Heat production, abdominal temperature, shank skin temperature and respiration rate were measured.

[22] BELAY T, THEETER R G . Broiler water balance and thermobalance during thermoneutral and high ambient temperature exposure. British Poultry Science, 1993, 72:116-124.
[本文引用: 1]

[23] RICHARDS S A . The significance of changes in the temperature of the skin and body core of the chicken in the regulation of heat loss
Journal of Physiology, 1971,216(1):1-10.
DOI:10.1113/jphysiol.1971.sp009505URLPMID:5558352 [本文引用: 1]
1. The relationship between the temperatures of the hypothalamus, colon and skin and the control of heat loss mechanisms at ambient temperatures from 20 to 40 degrees C has been studied in unanaesthetized .2. The temperatures of the core and feathered skin varied by not more than 5 degrees C throughout the full range of ambient temperature but the comb, shank and toe varied by up to 20 degrees C and exhibited wide fluctuations in constant environmental conditions.3. At an ambient temperature of 26-27 degrees C, the fluctuations ceased at all of the naked skin sites and there was evidence of a concurrent decrease in the tissue insulation of the extremities. No such change could be detected in the feathered skin.4. Analysis of the various body temperatures suggested that the onset of thermal panting was consistently related to the increment in hypothalamic temperature and that this relationship was influenced both by the peripheral and extra-cranial deep body temperatures.

[24] DONKOH A . Ambient temperature: a factor affecting performance and physiological response of broiler chickens
International Journal of Biometeorology, 1989,33(4):259-265.


[25] TZSCHENTKE B, NICHELMANN M, POSTEL T . Effects of ambient temperature, age and wind speed on the thermal balance of layer-strain fowls
British Poultry Science, 1996,37(3):501-520.
DOI:10.1080/00071669608417881URLPMID:8842458
1. In White Leghorn laying hybrids aged 14 to 399 d the effects were measured of ambient temperature (Ta) and wind speed (WS) on heat production (HP), evaporative heat loss (EHL), nonevaporative heat loss with or without considering heat storage (NEHL1 or NEHL2), conductance (c), total insulation (I) and colonic temperature (Tc) as well as on biological optimum temperature (BOT), thermoneutral temperature (TNT) and threshold temperature for evaporative heat loss (Te).

[26] YAHAV S, STRASCHNOW A, PLAVNIK I, HURWITZ S . Blood system response of chickens to changes in environmental temperature
Poultry Science, 1997,76(4):627-633.
DOI:10.1093/ps/76.4.627URLPMID:9106892
Abstract Hemodynamic changes were studied in broiler chickens during exposure to constant temperatures (10 to 35 C) or diurnal temperature cycles (10:30 C and 15:35 C), and during acute heat or cold. Packed cell volume (PCV) was significantly high at low constant temperatures (10 and 15 C), whereas at high temperatures (30 and 35 C) plasma volume (PV) was significantly high. A linear relationship between hematocrit and heart weight was observed and indicates an adaptation of heart mass to changes in cardiac output and hematocrit to meet the demands of increased basal metabolic rate. Only during the diurnal temperature cycle of 15:35 C did a significant increase in PV occur when ambient temperature (Ta) was raised form 15 to 35 C. Acute exposure of chickens to high temperature did not affect PV or PCV, but resulted in hyperthermia (44.7 +/- 0.4 C). Changes in PCV are probably related to modulation of the supply of oxygen to accommodate changes in heat production. The significant hypervolemia observed at high temperatures could occur to provide the fluid needed for heat dissipation by panting. The lack of response of the blood system to acute temperature changes may be at least partially responsible for the chickens' failure to control body temperature.

[27] YAHAV S . The effect of constant and diurnal cyclic temperatures on performance and blood system of young turkeys
Journal of Thermal Biology, 1999,24(1):71-78.
DOI:10.1016/S0306-4565(98)00042-4URL [本文引用: 1]
Plasma (T 3 ) concentration was positively correlated with feed intake and weight gain.

[28] GOEL N K, STOLEN R H , MORGAN SKIM J K, DAN K, PICKRELL G. Glossary of terms for thermal physiology. Second edition. Revised by The Commission for Thermal Physiology of the International Union of Physiological Sciences (IUPS Thermal Commission)
Pflugers Arch, 1987,410(4/5):567-587.
DOI:10.1364/OL.31.000438URLPMID:3324054 [本文引用: 1]
[No authors listed]

[29] SAVAGE M V, BRENGELMANN G L . Control of skin blood flow in the neutral zone of human body temperature regulation
Journal of Applied Physiology, 1996, 80(4):1249.
DOI:10.1029/97JC02180URLPMID:8926253 [本文引用: 1]
In humans, matching of heat loss and heat production in the "neutral" zone, defined operationally in terms of a range of skin temperatures (Tsk), is accomplished by regulation of skin blood flow (SkBF). Our studies were designed to reveal the characteristics of control of SkBF [from measurements of forearm blood flow (FBF)] in this zone. We controlled the temperature of water sprayed on most of the body of supine men and women at 33 or 35 degrees C in a square-wave pattern (15 min at each temperature) or a step pattern (60 min at 33 degrees C separated by short periods at 35 degrees C). FBF followed Tsk (0.5 ml.min-1.degrees C-1). Esophageal temperature changed approximately 0.11 degrees C with each 2 degrees C change in Tsk, falling with Tsk increase and vice versa. Little influence on FBF, < 0.1 ml.min-1.100 ml-1. degrees C-1, was observed when only the forearm was sprayed with 33 and 35 degrees C water. We conclude that SkBF control in the 33-35 degree C range of Tsk is dominated by the feedforward reflex influence of Tsk on SkBF. The reflex response overcompensates for the effect of Tsk on thermal balance in the neutral zone, so that equilibrium core temperature has an inverse relationship to Tsk.

[30] BRENGELMANN G L, SAVAGE M V . Temperature regulation in the neutral zone
Annals of the New York Academy of Sciences, 2010,813(1):39-50.
DOI:10.1111/j.1749-6632.1997.tb51670.xURLPMID:9100860
Not Available

[31] MEKJAVIC I B, EIKEN O . Contribution of thermal and nonthermal factors to the regulation of body temperature in humans
Journal of Applied Physiology, 2006,100(6):2065-2072.
DOI:10.1152/japplphysiol.01118.2005URLPMID:16410380 [本文引用: 1]
Abstract The set point has been used to define the regulated level of body temperature, suggesting that displacements of core temperature from the set point initiate heat production (HP) and heat loss (HL) responses. Human and animal experiments have demonstrated that the responses of sweating and shivering do not coincide at a set point but rather establish a thermoeffector threshold zone. Neurophysiological studies have demonstrated that the sensor-to-effector pathways for HP and HL overlap and, in fact, mutually inhibit each other. This reciprocal inhibition theory, presumably reflecting the manner in which thermal factors contribute to homeothermy in humans, does not incorporate the effect of nonthermal factors on temperature regulation. The present review examines the actions of these nonthermal factors within the context of neuronal models of temperature regulation, suggesting that examination of these factors may provide further insights into the nature of temperature regulation. It is concluded that, although there is no evidence to doubt the existence of the HP and HL pathways reciprocally inhibiting one another, it appears that such a mechanism is of little consequence when comparing the effects of nonthermal factors on the thermoregulatory system, since most of these factors seem to exert their influence in the region after the reciprocal cross-inhibition. At any given moment, both thermal and several nonthermal factors will be acting on the thermoregulatory system. It may, therefore, not be appropriate to dismiss the contribution of either when discussing the regulation of body temperature in humans.

[32] GILOH M, SHINDER D, YAHAV S . Skin surface temperature of broiler chickens is correlated to body core temperature and is indicative of their thermoregulatory status
Poultry Science, 2012,91:175-188.
DOI:10.3382/ps.2011-01497URLPMID:22184442 [本文引用: 1]
Extreme thermal conditions may dramatically affect the performance of broilers and other domestic animals, thereby impairing animal welfare and causing economic losses. Although body core temperature is the parameter that best reflects a bird's thermal status, practical and physiological obstacles make it irrelevant as a source of information on the thermal status of commercial flocks. Advances in the technology of infrared thermal imaging have enabled highly accurate, noncontact, and noninvasive measurements of skin surface temperature. Providing that skin surface temperature correlates with body temperature, this technology could enable acquisition of reliable information on the thermal status of animals, thereby improving diagnoses of environmental stress in a flock. This study of broiler chickens found a strong positive correlation between body core temperature and facial surface temperature, as recorded by infrared thermal imaging. The correlation was equally strong at all ages from 8 to 36 d during exposure to acute heat stress with or without proper ventilation and after acclimation to chronic heat exposure. A similar correlation was found by measurements in commercial flocks of broilers. Measurements of blood plasma concentrations of corticosterone, thyroid hormones, and arginine vasotocin confirmed that metabolic activity was low after acclimation to chronic exposure to heat, whereas ventilation was at least as efficient as acclimation in reducing thermal stress but did not impair metabolism. In light of these novel results, commercial benefits of infrared thermal imaging technology are suggested, especially in climate control for commercial poultry flocks. The application of this technique to other domestic animals should be investigated in future experiments.