Corn grain has a high starch content and is used as main energy source in ruminant diets. Compared with finely ground corn (FGC), steam-flaked corn (SFC) could improve the milk yield of lactating dairy cows and the growth performance of feedlot cattle, but the detailed mechanisms underlying those finding are unknown. The rumen microbiome breaks down feedstuffs into energy substrates for the host animals, and contributes to feed efficiency. Therefore, the current study was conducted to investigate the ruminal bacterial community changes of heifers fed differently processed corn (SFC or FGC) using 16S rRNA sequencing technologies, and to uncover the detailed mechanisms underlying the high performance of ruminants fed the SFC diet. The results revealed that different processing methods changed the rumen characteristics and impacted the composition of the rumen bacteria. The SFC diet resulted in an increased average daily gain in heifers, an increased rumen propionate concentration and a decreased rumen ammonia nitrogen concentration. The relative abundance of the phylum Firmicutes and Proteobacteria were tended to increase or significantly increased in the heifers fed SFC diet compared with FGC diet. In addition, the relative abundance of amylolytic bacteria of the genera Succinivibrio, Roseburia and Blautia were elevated, and the cellulolytic bacteria (Ruminococcaceae_UCG-014 and Ruminococcaceae_UCG-013) were decreased by the steam flaking method. Spearman correlation analysis between the ruminal bacteria and the microbial metabolites showed that the rumen propionate concentration was positively correlated with genera Succinivibrio and Blautia abundance, but negatively correlated with genera Ruminococcaceae_UCG-014 abundance. Evident patterns of efficient improvement in rumen propionate and changes in rumen microbes to further improve feed conversion were identified. This observation uncovers the potential mechanisms underlying the increased efficiency of the SFC processing method for enhancing ruminant performance.

中文翻译：

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微生物的特定富集和瘤胃丙酸的产生增加：荷斯坦小母牛饲喂蒸汽片状玉米的高能量效率的潜在机理。

玉米谷物中淀粉含量高，被用作反刍动物日粮中的主要能源。与细磨的玉米（FGC）相比，蒸汽片状的玉米（SFC）可以提高泌乳奶牛的产奶量和育肥牛的生长性能，但这些发现的详细机制尚不清楚。瘤胃微生物组将饲料分解为宿主动物的能量底物，并有助于提高饲料效率。因此，目前的研究是使用16S rRNA测序技术调查以不同加工玉米（SFC或FGC）饲喂的小母牛的瘤胃细菌群落变化，并揭示以SFC饲喂反刍动物的高性能的详细机制。结果表明，不同的加工方法改变了瘤胃的特性并影响了瘤胃细菌的组成。SFC饮食导致小母牛平均日增重，丙酸瘤胃浓度升高和瘤胃氨氮浓度降低。门的相对丰度与FGC日粮相比，饲喂SFC日粮的小母牛的硬脂体和Proteobacteria倾向于增加或显着增加。此外，属的细菌淀粉分解的相对丰度Succinivibrio，罗斯氏和Blautia均升高，并且所述纤维素分解菌（Ruminococcaceae_UCG - 014和Ruminococcaceae_UCG - 013）由蒸汽剥落方法降低。瘤胃细菌与微生物代谢产物之间的Spearman相关分析表明，瘤胃丙酸酯浓度与Succinivibrio和Blautia属呈正相关。丰度，但与Ruminococcaceae_UCG - 014丰度成负相关。确定了有效改善丙酸瘤胃和改变瘤胃微生物以进一步改善饲料转化率的明显模式。该发现揭示了SFC处理方法提高反刍动物性能的效率背后的潜在机制。