不同相对湿度对连续日增温下肉仔鸡生理指标的影响

摘要

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 were 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 with 6 replicates per group and 10 chickens per replicate. Adaptation period lasted for 7 days, and the tempera?ture was 20 ℃ while the RH was 60%. When the broilers were 29?day?old, RH was adjusted to 35%, 60%and 85% of three groups, respectively, until the end of this trial. The temperature in the environment controlled chambers was rises by 2 ℃ per day, and the trial period was 9 days. When the broilers were 37?day?old, the temperature in the environment controlled chambers was 38 ℃. During the experiment period, the broilers fed and drank water ad libitum, and non?contact physiological indicators were measured, while there was no stress to chickens. The results showed that there was inflection point temperature ( IPt) in core temperature ( CT) , earlobe temperature ( ET) , leg temperature ( LT) , respiratory rate ( RR) , feed intake ( FI) and drinking wa?ter ( DW) . The first indicator of reaction was LT, and the temperature was in the range from 24.6 to 25.1 ℃, followed by ET and CT, while the temperature was in the range from 25.0 ℃ to 25.1 ℃ and 25.5 to 26.4 ℃each. RR had two IPts (IPt1 and IPt2) which were in the range from 25.5 to 27.2 ℃ and 32.5 to 33.3 ℃. RR was increased with the increasing temperature above IPt1 , while decreased with increasing temperature above IPt2. FI and DW were changed in the range from 27.1 to 29.3 ℃ and from 29.2 to 29.5 ℃ respectively, FI and DW were decreased with increasing temperature above IPt. The IPt of FI in high humidity group was sig?nificantly higher than those in middle and low humidity group ( P<0.05) . The IPt2 of mortality rate ( MR) in high humidity group was significantly lower than those in middle and low humidity group ( P<0.05) . The IPts of CT, ET, LT, RR, FI and DW under high humidity were lower 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, whereas RH has a relatively minor effects on it. The upper critical temperature can be considered to be the IPt above which FI decreased and RT then increased. The upper critical temperatures of 4 to 5 weeks 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. When the broiler died, the differences between the highest value of CT and the constant values are in the range from 4.6 to 5.1 ℃. The 4 to 5 weeks old male broilers have different upper critical temperatures for dif?ferent physiological indices.