Feed is the greatest cost of animal production so reducing it is critical to increase producer profits. In ruminants, the microbial population within the gastrointestinal tract (GIT) is critical to nutrient digestion and absorption in both the rumen and the hindgut. The objective of this study was to determine the bacterial taxonomic profile of the rumen, cecum, and feces of feedlot steers at slaughter in order to link feed efficiency and the GIT bacterial populations from these 3 locations. Twenty commercial Angus steers were selected and divided into two groups according to their residual feed intake (RFI) classification determined during the feedlot-finishing period: high-RFI (n=10) and low-RFI (n=10). After the ruminal, cecal, and fecal samples were collected at slaughter, DNA extraction and 16S rRNA gene sequencing were performed on them to determine their bacterial composition. One-way ANOVA was performed on the animal performance data, alpha diversities, and bacterial abundances using RFI classification as the fixed effect. Overall, the ruminal bacterial population was the most different in terms of taxonomic profile compared to the cecal and fecal populations as revealed by beta diversity analysis (P<0.001). Moreover, bacterial richness (Chao1) was greatest (P=0.01) in the rumen of the high-RFI group compared to the low-RFI group. In contrast, bacterial richness and diversity in the intestinal environment showed that Chao1 was greater (P=0.01) in the cecum, and Shannon diversity index was greater in both the cecum and feces of low-RFI compared to high-RFI steers (P=0.01 and P<0.001, respectively). Ruminococcaceae was more abundant in the low-RFI group in the cecum and feces (P=0.01); and fecal Bifidobacteriaceae was more abundant in high-RFI steers (P=0.03). No correlations (P≥0.13) between any ruminal bacterial family and RFI were detected; however, Ruminococcaeae, Mogibacteriaceae, Christensenellaceae, and BS11 were negatively correlated with RFI (P<0.05) in the cecum and feces. Succinivibrionaceae in the cecum was positively correlated with RFI (P=0.05), and fecal Bifidobacteriaceae was positively correlated with RFI (P=0.03). Results collectively indicate that in addition to the ruminal bacteria, the lower gut bacterial population has a significant impact on feed efficiency and nutrient utilization in feedlot steers, therefore the intestinal bacteria should also be considered when examining the basis of ruminant feed efficiency.

中文翻译：

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饲料效率选择对来自商业饲养场的安格斯牛瘤胃，盲肠和粪便微生物组的影响。

饲料是动物生产的最大成本，因此降低饲料成本对提高生产者利润至关重要。在反刍动物中，胃肠道（GIT）中的微生物种群对于瘤胃和后肠的营养物质消化和吸收至关重要。这项研究的目的是确定屠宰场中肉牛场的瘤胃，盲肠和粪便的细菌分类学特征，以便将饲料效率与这三个地点的GIT细菌种群联系起来。根据在育肥场肥育期间确定的剩余饲料摄入量（RFI）分类，选择了20头商业安格斯公牛，分为高RFI（n = 10）和低RFI（n = 10）。屠宰后收集瘤胃，盲肠和粪便样品，对它们进行DNA提取和16S rRNA基因测序，以确定其细菌组成。使用RFI分类作为固定效应，对动物生产数据，α多样性和细菌丰度进行单向方差分析。总体而言，瘤胃细菌种群在分类学特征上与盲肠和粪便种群相比最不相同，正如β多样性分析（P <0.001）。此外，与低RFI组相比，高RFI组的瘤胃细菌丰富度（Chao1）最大（P = 0.01）。相比之下，肠道环境中细菌的丰富性和多样性表明，与高RFI牛相比，低RFI的盲肠和粪便中盲肠的Chao1更大（P = 0.01），香农多样性指数更高（P = 0.01和P <0.001）。Ruminococcaceae是在盲肠和粪便（低RFI组更丰富的P = 0.01）; 高RFI牛的粪便中双歧杆菌科更为丰富（P = 0.03）。无相关性（P在瘤胃细菌家族和RFI之间检测到≥0.13）; 然而，Ruminococcaeae，Mogibacteriaceae，Christensenellaceae，和BS11呈负RFI（相关P在盲肠和粪便<0.05）。盲肠中的琥珀酸弧菌科与RFI呈正相关（P = 0.05），粪便双歧杆菌科与RFI呈正相关（P= 0.03）。结果共同表明，除瘤胃细菌外，较低的肠道细菌数量对育肥场公牛的饲料效率和养分利用率也有显着影响，因此在检查反刍动物饲料效率的基础时也应考虑肠道细菌。