The feeding of concentrate-rich diets may lead to microbial imbalances and dysfermentation in the rumen. The main objective of this study was to determine the effects of supplementing phytogenic compounds (PHY) or autolyzed yeast (AY) on rumen fermentation and microbial abundance in cows intermittently fed concentrate-rich diets. The experiment was carried out as an incomplete 3 × 4 Latin square design, with 8 nonlactating rumen-fistulated Holstein-Friesian cows. The cows were randomly assigned to a concentrate diet that was either not supplemented (CON), or supplemented with PHY or AY. Each of the 4 consecutive experimental periods was composed of a 1-wk roughage-only diet (RD), 6-d gradual concentrate increase, followed by 1 wk of 65% concentrate (dry matter basis; Conc I), and 1 wk of RD and a final 2-wk 65% concentrate (dry matter basis; Conc II) phase. Digesta samples were collected from the rumen mat for bacterial 16S rRNA gene Illumina MiSeq (Illumina, Balgach, Switzerland) sequencing, and samples of particle-associated rumen liquid were obtained for measuring short-chain fatty acids, lactate, ammonia, and pH during RD (d 6), Conc I (d 19), and Conc II (d 39). The concentrate feeding caused a decrease of overall bacterial diversity indices, especially during Conc I. The genera Ruminococcus, Butyrivibrio, and Coprococcus were decreased, whereas Prevotella, Megasphaera, Lachnospira, and Bacteroides were increased in abundance. Supplementation of both feed additives increased the abundance of gram-positive and decreased that of gram-negative bacteria. Supplementation of AY enhanced cellulolytic bacteria such as Ruminococcus spp., whereas PHY decreased starch and sugar fermenters including Bacteroides spp., Shuttleworthia spp., and Syntrophococcus spp. Moreover, PHY supplementation increased butyrate percentage in the rumen in both concentrate phases. In conclusion, intermittent high-concentrate feeding altered the digesta-associated rumen bacterial community and rumen fermentation with more significant alterations found in Conc I than in Conc II. The data also showed that both feed additives had the most significant modulatory effects on the bacterial community, and their subsequent fermentation, during periods of low pH.

饲喂富含浓缩物的饮食可能导致微生物失衡和瘤胃发育不良。这项研究的主要目的是确定间歇性饲喂富含浓缩饲料的奶牛中添加植物性化合物（PHY）或自溶酵母（AY）对瘤胃发酵和微生物丰度的影响。该实验以不完整的3×4拉丁方形设计进行，其中有8头非泌乳瘤胃瘤型荷斯坦奶牛。母牛被随机分配到不补充（CON）或不补充PHY或AY的浓缩饲料中。连续4个实验阶段中的每个阶段均由1周纯饲粮（RD），6天逐渐浓缩精矿，随后1周的65％精矿（以干物质为基础; Conc I）和1周的精炼日粮组成。 RD和最终的2周65％精矿（以干物质为基础；Conc II）阶段。从瘤胃垫中收集消化样品，用于细菌16S rRNA基因Illumina MiSeq（Illumina，Balgach，瑞士）测序，并获得与颗粒相关的瘤胃液体样品，用于测量RD期间的短链脂肪酸，乳酸，氨和pH （d 6），Conc I（d 19）和Conc II（d 39）。浓缩饲料的投喂导致总体细菌多样性指数的下降，特别是在Conc I时期。瘤胃球菌属，丁酸和Coprococcus均有下降，而普氏菌，巨型球菌，Lachnospira和拟杆菌的丰度增加。两种饲料添加剂的添加均增加了革兰氏阳性菌的丰度，并降低了革兰氏阴性菌的丰度。补充AY可增强纤维素分解细菌，如Ruminococcus spp。，而PHY则可降低淀粉和糖发酵剂，包括Bacteroides spp。，Shuttleworthia spp。和Syntrophococcus。spp。此外，在两个浓缩阶段，PHY补充剂均增加了瘤胃中丁酸酯的百分比。总之，间歇性高浓度喂养改变了与消化相关的瘤胃细菌群落和瘤胃发酵，在Conc I中比在Conc II中发现了更大的变化。数据还显示，在低pH值期间，两种饲料添加剂对细菌群落及其随后的发酵具有最显着的调节作用。