【作者】 李静；

【导师】 乔健；

【作者基本信息】 中国农业大学 ， 基础兽医学， 2004， 博士

【摘要】 随着集约化高密度畜禽生产的迅速发展，热应激对养殖业的危害愈加受到人们的关注。尽管已经确切证明人和哺乳动物血流动力学的改变对热应激发生发展和相关疾病过程有重要病理生理意义，但对于禽类，无论是热应激对血流动力学的影响还是其机制，都缺乏应有的研究。本试验首次对热应激对肉鸡血流动力学的影响进行研究，同时对热应激肉鸡血气指标和组织学等方面的变化进行了较为系统的动态观察。 1．37℃持续热应激对肉鸡血流动力学影响 在37℃持续热应激12 d的试验期间，动态检测股动脉收缩／舒张压、股动脉压最大变化速率（±dp／dt max）、肺动脉收缩／舒张压、右心室收缩／舒张压和右心室内压最大变化速率（RV±dp／dt max）等血液动力学指标，同时对肉鸡的生产性能等指标进行动态检测。结果显示热暴露使肉鸡平均股动脉压（16.97±0.41，11.03±1.98 kPa）极显著下降（P＜0.01），但7～9天时有回升趋势。热暴露早期股动脉收缩压最大变化速率极显著下降（P＜0.01），中后期股动脉收缩压最大变化速率显著或极显著升高（P＜0.05或P＜0.01）；热暴露早期股动脉舒张压最大变化速率显著下降（P＜0.05），但后期股动脉舒张压最大变化速率显著升高（P＜0.05）。热暴露1、5、7和12天时平均肺动脉压极显著下降（P＜0.01），3天时显著下降（P＜0.05），热暴露早期右心室收缩压极显著降低（P＜0.01）；中期显著降低（P＜0.05）；9天时，右心室收缩压极显著升高（P＜0.01）。热暴露后期，右心室舒张压极显著降低（P＜0.01）。热暴露期间，右心室内压最大变化速率都极显著降低（P＜0.01）。热应激期间，肉鸡日增重和日采食量极显著下降（P＜0.01）、料肉比极显著升高（P＜0.01）；呼吸频率极显著升高（P＜0.01）；热暴露第1，5，7，9和12 d体温极显著升高（P＜0.01）。平均股动脉压与呼吸频率、体温极显著负相关（（?）0.667，（?）0.644；P＜0.01）。平均肺动脉压与平均股动脉压极显著相关（P＜0.01）；与呼吸频率和体温极显著负相关（P＜0.01）。结果表明37℃持续热应激严重影响肉鸡血液动力学，血流动力学的改变尤其是动脉压的显著下降（相当于人的低血压）可能会直接影响组织血液的灌流量，甚至引起组织缺血，从而影响血气、酸碱平衡、组织形态学、器官功能和生产性能。股动脉压的变化与肉鸡对热暴露的反应和适应过程密切相关。 2．37℃持续热应激对肉鸡血气和酸碱平衡的影响 在37℃持续热应激12 d的试验期间，动态检测热应激肉鸡血气指标、呼吸频率、直肠温度和生产性能的变化。结果显示，热暴露初期呈现代偿性呼吸性碱中毒，其特点为动脉血二氧化碳分压（3.82±0.36）降低，pH（7.48±0.04）升高；中期呈现失代偿性代谢性酸中毒，其特点为血浆HCO₃^-1浓度（19.00±2.55）降低，pH（7.37±0.06）显著下降（P＜0.05）；后期酸碱平衡趋于正常。动脉血氧分压与呼吸频率呈极显著负相关（P＜0.01），与体温呈显著负相关（P＜0.05）；血氧饱和度与体温极显著负相关（P＜0.01）。表明37℃持续热应激的肉鸡呈现由代偿性呼吸性碱中毒转变为失代偿性代谢性酸中毒，最后趋于正常的动态变化过程。 3.37℃持续热应激对肉鸡组织形态学的影响 在37℃持续热应激12d的试验期间，动态观察肉鸡肺、气管、肝、腺胃、十二指肠、胰腺、心、肾、大脑、胸腺、脾脏、甲状腺、肾上腺和法氏囊的组织形态学变化。试验表明，热应激肉鸡早期主要出现肺和气管充血、水肿，心、肝、肾实质细胞变性，十二指肠绒毛上皮脱落，胸腺出血等组织形态学变化;中期主要出现肺淤血、渗出，气管粘膜上皮微绒毛消失，十二指肠绒毛断裂，心肌小灶状出血，肝空泡变性，肾颗粒变性，甲状腺滤泡间出血，肾上腺出血，免疫器官淋巴细胞减少等组织形态学变化;后期肺、气管、十二指肠、肝、肾、甲状腺和肾上腺的组织形态学变化减轻，但其它器官尤其免疫器官仍有较严重的形态学变化。提示肉鸡已经有一定的代偿和适应，但有些器官器质性的变化在短期内难以恢复。 4.38.5℃、40℃和42℃持续热应激对肉鸡血流动力学的影响 4.1 38.5℃持续7天热应激期间，肉鸡平均股动脉压、股动脉收缩压和股动脉舒张压在早期和后期出现显著或极显著下降;肉鸡平均肺动脉压、肺动脉收缩压和肺动脉舒张压显著或极显著下降;热暴露早期和后期右心室收缩压降低;热应激第3天时右心室收缩压显著升高。平均肺动脉压与平均股动脉压极显著相关:与体温极显著负相关. 4.2 40℃持续热暴露10h期间，肉鸡平均股动脉压、股动脉收缩压和股动脉舒张压极显著下降。第10h时平均股动脉压、股动脉收缩压和股动脉舒张压下降幅度最大。 4.342℃持续热应激50 min期间，肉鸡平均股动脉压、股动脉收缩压和股动脉舒张压显著或极显著下降。热暴露第50分钟时平均股动脉压、股动脉收缩压和股动脉舒张压下降幅度最大。 总之，本试验从宏观整体的角度对热应激对肉鸡血流动力学、组织形态学和血气指标等方面的影响及机制进行了比较系统的研究，首次发现血流动力学指标是肉鸡热应激发生发展过程中最大的变数之一，这将添补国内外关于热应激对肉鸡血流动力学影响研究的空白，?更多还原

【Abstract】 The purpose of the experiment was to study the effects of constant heat-stress on the hemodynamics and acid-base balance in broiler chickens.1. The effects of 37℃ constant heat-stress on the hemodynamics in broiler chickensIn the period of 37℃ 12 days constant heat-stress, the femoral artery systolic/diastolic pressure, the maximum increasing rate of femoral artery (眃p/dt max), the pulmonary artery systolic/diastolic pressure, the right ventricular systolic/diastolic pressure, the maximum increasing rate of right ventricular (RV眃p/dt max), the production performance, and etc. of broiler chickens in different groups were examined continuously. The mean femoral artery pressure (mFAP, 16.97+0.41, 11.03+1.98 kPa) of the birds in the treated group decreased significantly (P <0.01), but there was an uptrend between 7~9 days after thermostress. The maximum increasing rate of femoral artery systolic pressure (+dp/dt max) decreased significantly (P <0.01) in the prophase, but increased significantly in the metaphase (P <0.05) and anaphase (P<0.01); The maximum increasing rate of femoral artery diastolic pressure ( | -dp/dtmax | ) decreased significantly (P<0.05) in the prophase, but increased significantly in the anaphase (P<0.05). The mean pulmonary artery pressure (mPAP) decreased significantly (P<0.01) at 1,5,7 and 12 days after thermostress, and decreased significantly (P <0. OS) at 3 days after thermostress. The right ventricular systolic pressure decreased significantly in the prophase (P<0.01) and metaphase (P<0.05), but increased significantly (P<0.01) at 9 days after thermostress. The right ventricular diastolic pressure decreased significantly (P<0.01) in the anaphase. During the experiment, the RV I 眃p/dtmax I decreased significantly (P<0.01). Body weight gain and feed intake of thermostressed chickens were decreased significantly (P<0.01), and feed/gain was increased significantly (P<0.01); The respiration rate and rectal temperature of heat-stressed broiler chickens were increased significantly (P <0.01) at 1, 5,7,9 and 12 days after thermostress. The mFAP had a significantly negative correlation with respiration rate and rectal temperature (r=-0.667, r=-0.644; P<0.01) ; The mPAP had a significantly negative correlation with mFAP, respiration rate and rectal temperature (P<0.01). These results showed that there are significant hemodynamics disturbance, severely affected physiological function and decreased production performance in the broiler chickens under 37℃ constant heat-stress. The change of FAP is close to the response and adaptation of chickens to thermostress.2. The effects of 37℃ constant heat-stress on the blood gas and acid-base balance in broiler chickensIn the period of 37℃ 12 days constant heat-stress, the blood gas, respiration rate, rectal temperature and production performance of broiler chickens in different groups were examined continuously. Twenty-four hours after thermostress there was a compensated respiratory alkalosis, which was characterized by the decreased partial pressure of CO2 (PaCO2, 3.82+0.36) and the increasedpH (7.48+0.04) in artery. Seven days after thermostress there was a decompensated metabolic acidosis, which was characterized by the dropped arterial blood bicarbonate ion (HCO3-1, 19.00+2.55) and the decreased pH value (7.37+0.06,P <0.05). Twelve days after thermostress acid-base balance was almost resumed. The oxygen partial pressure (PaO2) had a significantly negative correlation with respiration rate (P<0.01) and rectal temperature (P<0.05); The arterial blood oxygen saturation (SaO2) had a significantly negative correlation with rectal temperature (P<0.01). These results showed that there are a significant acid-base balance disturbance, severely affected physiological function and decreased production performance in the broiler chickens under 37℃ constant heat-stress.3. The effects of 37℃ constant heat-stress on the tectology in broiler chickensIn the period of 37℃ 12 days constant heat-stress, the dynamic change of tectolog更多还原