Research on adaptation for hot environment by dairy cow

在高温环境下，比较了荷斯坦牛与日本黑牛杂交一代（F1）和荷斯坦牛（H）的几项生理指标的适应性。试验用8月龄H和F_1代犊牛各2头。小牛在人工气候室中暴露于高温（30 ℃）下2天。测量总可消化营养素（TDN）摄入量和直肠温度（RT），并记录呼吸速度描记图和心电图。通过颈静脉采集血液样本。血液样本用于测量红细胞压积（PCV）、血红蛋白浓度（Hb）、红细胞计数（RBC）和白色血细胞计数（WBC）。其他血样分离至血浆中，用于测定血浆中总蛋白（TP）、葡萄糖（Glc）、游离脂肪酸（FFA）和N-甲基组氨酸（MeHis）的浓度。TDN摄入量减少热应激，尤其是在H犊牛。热胁迫使H的RT升高到40-41 ℃，而F则保持在40 -41 ℃， ...更多信息 室温39 ℃。呼吸频率（RR）在两个小牛增加热应激。30 ℃处理第1天至第2天，F_1的RR增加，而mH下降。热应激使F_1的心率（HR）增加，而荷斯坦牛的心率（HR）降低。由此推测，荷斯坦牛尽管TDN和HR的降低表明产热减少，但RT仍有升高的趋势，而F_1则可通过增加喘息来避免RT的升高。热应激对红细胞压积、血红蛋白、红细胞、白细胞、总蛋白和游离脂肪酸的影响不明显。而TP在荷斯坦犊牛中高于F_1代。在整个实验期间，血浆Glc水平维持在正常范围内。热应激使两头犊牛血浆MeHis升高。热应激使荷斯坦奶牛血浆MeHis含量升高，其幅度大于F_1代。特别是在H-1中，MeHis和TDN的摄入量发生了很大变化。已知能量缺乏动物的血浆MeHis由于肌原纤维蛋白降解而增加，并且血液中肌原纤维释放的MeHis增加。因此，推测本研究中热应激引起的MeHis增加部分是由于TDN摄入量减少所致。结果表明，F_1的耐热性上级优于荷斯坦牛，其耐热性特征表现为有效热损失。少

Under hot environment, adaptability of crossbred cattle between Holstein and Japanese black (F1) and Holstein cattle (H), was compared, on several physiological parameters. Experiments were carried out using two H and F_1, calves aged 8 months. The calves were exposed to high temperature (30 ℃) for two days in the climatic chamber. Total digestible nutrients (TDN) intake and rectal temperature (RT) were measured and pneumotachogram and electrocardiogram were recorded. Blood samples were taken via jugular vein Blood samples were used for measurement of packed cell volume (PCV), hemoglobin concentration (Hb), red blood cell count (RBC), and white blood cell count (WBC). The other blood samples was separated to plasma for measurement of plasma concentration of total protein (TP), glucose (Glc), free fatty acid (FFA), and Nmethylhistidine (MeHis). TDN intake was decreased by heat stress, especially in H calves. RT in H was elevated to 40-41 ℃by heat stress, while that in F, was kept on abo … More ut 39 ℃. Respiratory rate (RR) in both calves was increased by heat stress. However, from first day to second day of 30 ℃, RR in F_1 was increased but that m H decreased. Heart rate(HR) in FI was increased by heat stress, while Holstein was decreased From these results, it is presumed that Holstein obliged to suffer the elevation of RT in spite of the decrease in heat production suggested from the decrease in TDN and HR. While F_1 could avoid the elevation of RT by the promotion of heat loss estimated from the increase in panting. The influence of heat stress on PCV, Hb, RBC, WBC, TP, and FFA in the both calves were almost not recognized. However, TP in Holstein calf were higher than that in F_1. Plasma Glc levwls were maintained within normal range through experimental periods. Plasma MeHis in the both calves was increased by heat stress. Plasma MeHis of Holstein was more increased by heat stress than that of F_1. Especially, MeHis as well as TDN intake in H-1 was greately changed. It is known that plasma MeHis of animal under energy deficient is increased due to myofibrillar protein degradation and MeHis released from myofibril increase in blood. It was presumed, therefore, that the increase in MeHis by heat stress in this study were partially caused due to decreased TDN intake. The results of this study suggest that F_1 is superior in heat tolerance to Holstein, and the characteristics of the heat tolerance in F1 are represented as the effctiv heat loss. Less