本文旨在研究不同季节牧草营养成分变化及藏系绵羊瘤胃细菌区系的季节动态变化。试验在不同季节分别随机选取3只藏系绵羊，采用PCR-DGGE技术对12只藏系绵羊瘤胃内容物中的细菌区系进行分子生态学的分析，对细菌16S rDNA的V6-V8可变区的扩增产物进行DGGE图谱分析、相似性分析和Shannon多样指数分析。结果表明：（1）秋季瘤胃细菌种群丰富度极显著（P<0.01）高于冬、春季节，显著（P<0.05）高于夏季，而其他3个季节之间差异不显著（P>0.05）；（2）瘤胃细菌区系组成结构在春季和夏季相似性高于90%，在秋、冬季相似性低于70%，而春、夏季与秋、冬季之间的相似性低于60%；（3）夏季牧草中DE和CP含量极显著（P<0.01）高于其他季节，其瘤胃液pH极显著（P<0.01）低于其他季节，瘤胃细菌区系丰富度也相应降低；秋季牧草的DE和CP含量显著（P<0.05）高于春、冬季节，其瘤胃液pH范围为7.1-7.3，瘤胃细菌区系丰富度高于其他3个季节。由以上结果可以看出，不同季节瘤胃内优势菌群发生了改变，瘤胃细菌区系的季节变化与瘤胃pH、瘤胃内容物的物理特性、营养成分及其比例等有关。

This experiment was conducted to study the changes of forage nutrient content and seasonal shift of bacterial community in rumen of the grazing Tibetan sheep. PCR and denaturing gradient gel electrophoresis (DGGE) were used to monitor changes of bacterial community in rumen of 12 Tibetan sheep. The V6～V8 regions of the 16S rDNA of rumen bacteria were amplified. DGGE profiles of the PCR amplicons were compared by similarity analysis. Shannon diversity index of the bacterial community was also performed. Results showed: 1) in autumn, the structural diversity of bacterial community was significantly higher than that in winter (P<0.01), spring (P<0.01) and summer (P<0.05) and there were no significant differences among winter, spring and summer (P>0.05); 2) rumen bacterial community changed with seasonal shift. Similar rate between autumn and summer was higher than 90%; similar rate between autumn and winter was less than 70% and similar rate between spring, summer and autumn, winter was less than 60%; 3) the CP and DE content of forages in summer were significantly (P<0.01) higher than those in other seasons, but the pH of rumen in summer was significantly (P<0.01) lower than that in other seasons, and the structural diversity of the bacterial community also reduced. The CP and DE content of forages in autumn were significantly (P<0.05) higher than that in winter and spring. The pH of rumen in autumn were from 7.1 to 7.3, and the structural diversity of the bacterial community were higher than that in other seasons. It was concluded that bacterial community in rumen of the grazing Tibetan sheep changed with seasonal shift, which were affected by pH in rumen, rumen physical characteristics and nutritional ingredient.［Chinese Journal of Animal Nutrition, ２００9，２1（5）:798-802］