海拔高度变化对牦牛血细胞生理指标及心、肺组织形态特征的影响

Effect of Altitude Changes on Blood Cell Physiological Parameters and Cardiopulmonary Histomorphological Characteristics of Yaks

川西高原传统放牧养殖的牦牛生产效率低下,却受制于地形与运输成本不适于集约化舍饲育肥,而临近的成都平原能提供较好的舍饲养殖条件和场地。该试验将牦牛从川西高原高海拔地区(3500 m)迁移至成都平原低海拔地区(500 m),研究迁移后不同时间点牦牛血液生理指标和血清皮质醇浓度的变化规律,并通过HE切片比较海拔高度变化对牦牛心脏和肺脏组织形态特征的影响,为合理指导牦牛迁移至低海拔地区饲养提供理论参考。结果表明:(1)牦牛从高海拔地区向低海拔地区转移后,红细胞比积(HCT)、血红蛋白含量(HGB)、平均血红蛋白含量(MCH)、平均血红蛋白浓度(MCHC)随时间延长显著降低(P<0.05),白细胞数量(WBC)、淋巴细胞数量(LYC)和粒细胞数量(GRC)先升高后降低(P<0.05),血清皮质醇含量极显著升高(P<0.001);(2)低海拔地区牦牛心肌纤维密度和肺泡间隔厚度比高海拔地区牦牛显著下降(P<0.05),平均肺泡截距显著升高(P<0.05),肺泡数量显著高于低海拔舍饲黄牛(P<0.05)。试验结果说明,牦牛从高海拔迁移至低海拔后,血液携氧能力降低,迁移初期HCT、HGB、MCH和MCHC含量降低,WBC、LYC、GRC和血清皮质醇含量增加,并通过降低心肌纤维密度和肺泡间隔厚度以及提升平均肺泡截距,以适应低海拔富氧环境。

Yaks raised by grazing in western Sichuan Plateau areas show very low production efficiency.Intensive house feeding of yaks is not applicable due to terrain and transportation costs in this area.However,the nearby Chengdu plain can provide better conditions with sufficient feed resources and suitable places for house-feeding.Therefore,the current experiment was conducted to investigate the dynamics of yak blood cell physiological parameters and serum cortisol concentration after transition from high altitude area of Western Sichuan Plateau(3500 m)to low altitude area of Chengdu Plain(500 m).The effect of altitude alteration on cardiopulmonary histomorphology were also compared among the low-altitude yaks,high-altitude yaks and low-altitude yellow cattle by histology,which could provide valuable practical guidance for remote transportation and feeding yaks from high altitude area to low altitude area.The results of blood physiological indicators showed that during the transition from the high-altitude area to the low altitude area,the hematocrit(HCT),Hemoglobin(HGB),mean corpuscular hemoglobin(MCH)and mean corpuscular hemoglobin concentration(MCHC)of yaks significantly decreased with time(P<0.05),whereas the white blood cell(WBC),Lymphocyte count(LYC),Granulocyte count(GRC)increased first and then decreased(P<0.05).Moreover,the serum cortisol showed a significant linear increase trend(P<0.001).The results of cardiopulmonary morphological sections showed that the density of myocardial fiber and the thickness of alveolar septum of the low-altitude yaks decreased significantly(P<0.05),whereas the mean alveolar intercept increased significantly compared with the high-altitude counterparts(P<0.05).However,yaks from both areas exhibited significantly greater number of alveoli compared with the cattle from low altitude area(P<0.05).These results indicate that the transition from high-altitude area to low-altitude area reduces the blood oxygen-carrying capacity of yaks.In the early stage of migration,the HCT,HGB,MCH and MCHC decrease;the WBC,LYC,GRC,MC and serum cortisol levels increase;the myocardial fiber density and the thickness of the alveolar septum decrease,and the mean alveolar intercept increase,so that the yaks can adapt to the oxygen-rich environment at low-altitude.