夏季高温环境和遮阳对夏南牛血液生理生化指标和行为的影响

Effects of High Temperature Environment and Shading in Summer on Blood Physiological and Biochemical Indexes and Behavior of Xianan Cattle

为研究夏季高温对夏南牛生理生化和行为的影响以及遮阳网的抗热应激效果,该试验采用2×2双因素试验设计,挑选16头体重相近(289.63±27.32)kg且健康状态良好的夏南牛,分别在夏季和秋季进行试验,且每个季节分为遮阳处理和不遮阳处理2组(n=8)。结果表明:(1)夏季组平均温湿度指数(temperature-humidity index,THI)为76.87,通过架设遮阳网,THI降低至75.10,秋季组平均THI为61.63,秋季遮阳网组为61.10;(2)夏季遮阳网组和秋季夏南牛的直肠温度和呼吸频率显著低于夏季组(P<0.05);(3)与夏季组相比,秋季夏南牛血清中热休克蛋白70(heat shock protein 70,HSP70)、热休克蛋白90(HSP90)和皮质醇(cortisol,COR)的含量显著降低(P<0.05),超氧化物歧化酶(superoxide dismutase,SOD)、总抗氧化能力(total antioxidant capacity,T-AOC)、三碘甲腺原氨酸(T 3)以及甲状腺素(T 4)含量显著增加(P<0.05);(4)与夏季组相比,夏季遮阳网组夏南牛的饮水次数显著降低(P<0.05),游走时间和躺卧时间减少,秋季组和秋季遮阳网组夏南牛的躺卧时间、采食时间显著增加(P<0.05),饮水次数和游走站立时间显著减少(P<0.05);(5)呼吸频率、直肠温度与热休克蛋白表达水平、抗氧化指标呈负相关,与行为学存在一定的相关性。综上所述,在夏季高温条件下,夏南牛行为变化异常,呼吸频率加快,直肠温度升高,血浆中COR和HSPs含量增加,抗氧化能力下降,可能发生热应激反应,架设遮阳网后有效地降低了夏南牛的呼吸频率和直肠温度,且血浆中皮质醇含量和热休克蛋白含量减少,抗氧化能力增强,说明遮阳网处理能在一定程度上缓解夏南牛热应激。

The objective of this study was to investigate the effects of high temperature in summer on physio-biochemical indexes and behavior of Xianan cattle,and the anti-heat stress effect of shading.In this experiment,a 2×2 two-factor design was used,16 healthy Xianan cattle with similar weight(289.63±17.32)kg were selected.Experiments were carried out in summer and autumn,and were divided into two groups:shading treatment and non-shading treatment(n=8)for each season.The results indicated as follows:(1)the average THI in summer group was 76.87,the THI reduced to 75.10 by setting up the shading,the average THI in autumn group was 61.63 and the average THI of shading group in autumn was 61.10.(2)Compared with summer group,the rectal temperature and respiratory rate of Xianan cattle of shading group in summer decreased significantly(P<0.05).(3)Compared with summer group,the serum Heat shock proteins 70(HSP70),Heat shock proteins 90(HSP90),Cortisol(COR)contents of Xianan cattle in the two autumn groups were significantly decreased(P<0.05),and the contents of Super Oxide Dismutase(SOD),Total antioxidant capacity(T-AOC),Triiodothyronine(T 3),Thyroxine(T 4)significantly increased(P>0.05).(4)Compared with summer group,the water drinking frequency decreased significantly in shading group in summer(P<0.05),and walking time and lying time decreased(P>0.05).Compared with summer group,the lying time and feeding time of the two autumn groups increased significantly(P<0.05),and the water drinking frequency and feeding time decreased significantly(P<0.05).(5)Through the correlation analysis of various indexes,it was found that respiratory rate,rectal temperature and heat shock protein expression levels were negatively correlated with antioxidant indexes,and there was a certain correlation with behavior.To sum up,under the condition of high temperature in summer,the behavior of Xianan cattle changes,its respiratory rate speeds up and the rectal temperature,COR and HSPs content in plasma increase,while the antioxidant ability decreases,this indicates that heat stress reaction may occur in Xianan cattle.After setting up the shading net,the respiratory rate and rectal temperature of the Xianan cattle are effectively reduced,the cortisol content and heat shock protein content in the plasma are reduced,and the antioxidant capacity is enhanced,which means that the shading treatment can relieve the heat stress of Xianan cattle to a certain extent.