不同相对湿度对连续日增温下肉仔鸡生理指标的影响

Effects of Different Relative Humidity on Physiological Indices of Broilers under Continuous Increasing Temperature

本试验研究了不同相对湿度(RH)对日增温环境中肉仔鸡生理指标的影响。试验选取22日龄爱拔益加(AA)肉仔公鸡180只转入人工气候试验舱,随机分成3个组,每组6个重复,每个重复10只鸡。适应期7 d,温度20℃,RH为60%。肉鸡29日龄时,试验RH分别调整到35%、60%和85%,至试验结束。环控舱内温度每天升高2℃,试验期共9 d。肉鸡37日龄时,环控舱舱内温度升高至38℃,试验期间肉鸡自由采食饮水,试验全程不抓鸡,选择非接触性生理指标进行测定,以尽量避免肉鸡产生应激。结果表明:肉鸡体核温度(CT)、耳叶温度(ET)、小腿温度(LT)、呼吸频率(RR)、采食量(FI)和饮水量(DW)均存在拐点温度(IPt)。首先变化的是LT,其产生变化的环境温度范围是24.6~25.1℃,之后是ET和CT,发生变化的环境温度范围分别是25.0~25.1℃和25.5~26.4℃。RR存在2个IPt(IPt1和IPt2),温度范围分别是25.5~27.2℃和32.5~33.3℃。环境温度大于IPt1值时,RR随温度升高而升高;环境温度大于IPt2值,RR随温度升高而下降。FI、DW发生变化的环境温度范围分别为27.1~29.3℃和29.2~29.5℃,环境温度大于IPt值后,FI和DW随温度升高而降低。高湿组FI的IPt值显著高于低湿组和中湿组(P<0.05),高湿组死亡率(MR)的IPt2值显著小于低湿组和中湿组(P<0.05),高湿组CT、ET、LT、RR、FI和DW的IPt值小于中湿组和低湿组,RH对ET、LT、RR和DW模型参数均无显著影响(P>0.05)。结果提示:环境温度对肉仔鸡生理指标影响较大,RH影响较小。FI下降和CT升高的IPt值可被认为是上限临界温度,4~5周龄肉仔公鸡CT上限临界温度为25.5~26.4℃;RR开始升高和FI开始下降的上限临界温度分别为25.5~27.2℃和27.1~29.2℃;死亡的上限临界温度在为32.7~33.5℃。肉仔鸡死亡时CT高出常数值4.6~5.1℃。4~5周龄肉仔公鸡不同生理指标有着不同的上限临界温度。

In this study,the effects of different relative humidity( RH) on the physiological indices of broilers under increasing temperature environment w ere studied. One hundred and eighty 22-day-old Arbor Acres( AA) male broilers were allotted into environment controlled chambers and randomly divided into 3 groups w ith 6 replicates per group and 10 chickens per replicate. Adaptation period lasted for 7 days,and the temperature w as 20 ℃ w hile the RH w as 60%. W hen the broilers w ere 29-day-old,RH w as adjusted to 35%,60%and 85% of three groups,respectively,until the end of this trial. The temperature in the environment controlled chambers w as rises by 2 ℃ per day,and the trial period w as 9 days. W hen the broilers w ere 37-day-old,the temperature in the environment controlled chambers w as 38 ℃. During the experiment period,the broilers fed and drank w ater ad libitum,and non-contact physiological indicators w ere measured,w hile there w as no stress to chickens. The results show ed that there w as inflection point temperature( IPt) in core temperature( CT),earlobe temperature( ET),leg temperature( LT),respiratory rate( RR),feed intake( FI) and drinking w ater( DW). The first indicator of reaction w as LT,and the temperature w as in the range from 24.6 to 25.1 ℃,follow ed by ET and CT,w hile the temperature w as in the range from 25.0 ℃ to 25.1 ℃ and 25.5 to 26.4 ℃each. RR had tw o IPts( IPt1 and IPt2) which were in the range from 25.5 to 27.2 ℃ and 32.5 to 33.3 ℃. RR w as increased w ith the increasing temperature above IPt1,while decreased with increasing temperature above IPt2. FI and DW w ere changed in the range from 27. 1 to 29. 3 ℃ and from 29. 2 to 29. 5 ℃ respectively,FI and DW w ere decreased w ith increasing temperature above IPt. The IPt of FI in high humidity group w as significantly higher than those in middle and low humidity group( P< 0.05). The IPt2 of mortality rate( M R) in high humidity group w as significantly low er than those in middle and low humidity group( P< 0.05). The IPts of CT,ET,LT,RR,FI and DW under high humidity w ere low er than those in middle and low humidity group. RH had no significant effect on ET,LT,RR and DW model parameters( P > 0. 05). In conclusion,ambient temperature strongly affects the physiological indices of broilers,w hereas RH has a relatively minor effects on it. The upper critical temperature can be considered to be the IPt above w hich FI decreased and RT then increased. The upper critical temperatures of 4 to 5 w eeks old broilers are from 25. 5 to 26. 4 ℃ for CT,from 25.5 to 27.2 ℃ for RR decreased,from 27.1 to 29.2 ℃ for FI increased,and from 32.7 to 33.5 ℃ for death. W hen the broiler died,the differences betw een the highest value of CT and the constant values are in the range from 4.6 to 5.1 ℃. The 4 to 5 w eeks old male broilers have different upper critical temperatures for different physiological indices.[Chinese Journal of Animal Nutrition,2017,29( 10) : 3514-3522]