热应激对奶牛瘤胃液微生物数量的影响

Effects of Heat Stress on Microbial Number in Rumen Fluid of Dairy Cows

本试验采用实时荧光定量PCR技术研究热应激对不同泌乳阶段奶牛瘤胃液微生物数量的影响。采用2×3交叉试验设计,根据胎次、平均泌乳天数和产奶量相近的原则,选择18头经产中国荷斯坦奶牛,分为泌乳前期(产后15～100 d)组、泌乳中期(产后112～175 d)组、泌乳后期(产后200～230 d)组,每组6个重复,根据实测的牛场温湿指数(THI)变化,采用热应激与非热应激的自身对照试验。结果表明:与非热应激期相比,热应激极显著提高了泌乳前期组奶牛瘤胃液各类微生物数量(P<0.01),极显著提高了泌乳后期组奶牛瘤胃液黄化瘤胃球菌数量和泌乳中期组的产琥珀酸拟杆菌数量(P<0.01),极显著降低了泌乳中、后期组的总细菌数量、白色瘤胃球菌数量和泌乳后期组的产琥珀酸拟杆菌数量(P<0.01)。整个热应激期THI与泌乳前期组奶牛瘤胃液总细菌数量(P<0.01)、厌氧真菌数量(P<0.05)、白色瘤胃球菌数量(P<0.01)和黄化瘤胃球菌数量(P<0.05)有较强的相关性,而THI与泌乳中、后期组奶牛的这些指标相关性较差。综上所述:1)泌乳前期组奶牛热应激期的瘤胃液各类微生物数量均极显著高于非热应激期,但对泌乳中、后期组的各类微生物数量影响无规律性。2)泌乳前期组奶牛瘤胃液微生物数量对热应激的反应更敏感。

This experiment was conducted to investigate the effects of heat stress on microbial number in rumen fluid of dairy cows during different lactating periods by real-time fluorescence quantitative PCR. A 2 x 3 cross- over design was used and eighteen healthy Chinese Holstein cows were selected. The cows were allocated into three groups based on their parity, average days in milk and milk yield： early lactation （postpartum 15 to 100 days） group, mid-lactation （postpartum 112 to 175 days） group and late lactation （postpartum 200 to 230 days） group, and six cows were in each group. A self-control trial between heat stress period and non-heat stress period was used based on temperature and humidity index （THI） measurement on site. The results showed as follows ： compared with non-heat stress period, heat stress significantly increased the microbial num- ber in early lactation group, the number of Ruminococcus flavefaciens in late lactation group and the number of Bacteroides succinogenes in mid-lactation group （P 〈0.01 ）. The number of total bacteria and Ruminococcus albus in mid- and late lactation groups and the number of Bacteroides succinogenes in late lactation group were significantly decreased by heat stress （ P 〈 0.01 ）. There were strong correlations between THI and the number of total bacteria （ P 〈 0.01 ）, anaerobic fungi （ P 〈 0.05 ）, Ruminococcus albus （ P 〈 0.01 ） and Ruminococ- cus flavefaciens （ P 〈 0.05 ） in rumen fluid of dairy cows in early lactation group, but the correlations between TH! and these indexes in mid- and late lactation groups were poor. Conclusions ： 1 ）heat stress significantly in- creases the microbial number in early lactation group compared with non-heat stress period, but there are no regularity effects of heat stress on microbial number in mid- and late lactation groups ; 2 ） it is indicated that the tureen microbial number in early lactation group is more sensitive to heat stress.