热应激条件下荷斯坦奶牛后段肠道差异微生物分析

本试验旨在分析热应激条件下，热应激耐受奶牛和热应激易感奶牛后段肠道菌群组成的差异，寻找与热应激相关的后段肠道微生物，为利用饲养管理和遗传选择等手段提高奶牛耐热能力提供理论依据。选择体况相近且健康的1胎中国荷斯坦泌奶牛19头，利用奶牛夏季上午直肠温度（MRT）和下午直肠温度（ART）差值（RTD）将其分为热应激易感组（H组，10头）和热应激耐受组（L组，9头）。采用Illumina PE250测序平台测定两组个体粪便中细菌16S rDNA V3~V4区序列，利用生物信息学方法筛选两组个体的差异微生物。结果表明：①L组的Shannon指数和Chao1指数高于H组，但组间差异不显著（P>0.05）。②在门水平，两组个体的厚壁菌门（Firmicutes）、拟杆菌门（Bacteroidetes）和变形菌门（Proteobacteria）的相对丰度之和均占总菌的95%以上；在属水平，L组中YRC22和普雷沃氏菌属（Prevotella）的相对丰度显著高于H组（P<0.05），且YRC22、Prevotella的相对丰度与ART、RTD、呼吸评分（RS）、直肠温度极值（RTR）及流涎评分（DS）等5项热应激相关指标均呈负相关关系。③与热应激相关的6项指标（MRT、ART、RTD、RS、DS、RTR）中，RS、DS和MRT在冗余分析（RDA）结果中R2较大，表明这3项指标与奶牛后段肠道微生物菌群相关程度较大。综上所述，热应激影响奶牛后段肠道菌群结构，Prevotella是热应激相关的后段肠道微生物。

Analysis of Differences in Hindgut Microbiota of Holstein Dairy Cows During Heat Stress

The objective of this study was to analyze the differences of hindgut microbiota composition between heat stress sensitive cows and heat stress tolerant cows under heat stress condition, to find specific microbiota related to heat stress, and to provide the theoretical basis for improving thermotolerance of dairy cows via improving feeding management and genetic selection.Nineteen Chinese Holstein dairy cows which were in 1st lactation and with the similar body conditions were divided into two groups by the difference of morning and afternoon rectal temperature:Heat stress sensitive group (group H, n=10) and heat stress tolerant group (group L, n=9).The sequences of V3 and V4 region for 16S rDNA were sequenced by Illumina PE250 sequencing platform and bioinformatic methods were used to detect the differential microbiota.The results showed that:①The Shannon and Chao1 indexes in group L were higher than that in group H, but there was no significant diffference (P>0.05).②For phylum level, over 95% of the sequences in both groups of cows were assigned to Firmicutes, Bacteroidetes and Proteobacteria.For genus level, the relative abundances of YRC22 and Prevotella were significantly higher than that in group H (P<0.05), and Prevotella and YRC22 were negatively correlated to the heat stress related indexes:Afternoon rectal temperature (ART), rectal temperature difference (RTD), respiratory score (RS), rectal temperature range (RTR) and drooling score (DS).③Among the heat stress related indexes (morning rectal temperature (MRT, ART, RTD, RS, DS, RTR), RS, DS and MRT were highly correlated with the diversity of hindgut microbiota, as R2 values were top three of these six indexes in the RDA results.In conclusion, the abundance of hindgut bacteria were influenced by heat stress.Prevotella could be the hindgut microbiota related to heat stress in dairy cows.