This study aimed to characterize the rumen bacterial diversity of beef steers differing in the efficiency of nitrogen retention (ENR). Eight castrated steers and fitted with ruminal silicone - and duodenal T-type cannulas were used in a cross-over design with three consecutive periods and three diets. During each experimental period, nitrogen balance was measured, and based on the efficiency of N utilization data, steers were split into three ENR groups: high (HNR, 56.6% ± 3.3%, n = 10), medium (MNR, 45.8% ± 2.2%, n = 6), and low (LNR, 37.7% ± 1.9%, n = 8) using the NbClust package version 2.0.4 in R. Prevotellaceae, Lactobacillaceae, Leuconostocaceae, Clostridiales_Incertae_Sedis_XIII, Lachnospiraceae, and Peptostreptococcaceae were more abundant in LNR (P < 0.05) compared to HNR or MNR. Negative correlations were found between N retention and Mogibacterium, Anaerofustis, Butyrivibrio, Coprococcus, Hespellia, Lactonifactor and Lachnospiraceae (r ≤ −0.61; P ≤ 0.05). Prevotella, Hespellia, Lactonifactor, Lachnospiraceae_other, and Anaerobiospirillum were positively correlated between urinary N excretion (r > 0.55; P < 0.01), and negative correlations were found with Elusimicrobia, Victivallis and Treponema (r < −0.41; P < 0.05). The adjustment of the rumen bacterial community differed significantly between the N use retention groups. The high N retention in beef cattle was associated with less abundant bacteria in the rumen; however, N fixation capacity and uncharacterized rumen microorganisms need to be elucidated in future studies. In contrast, lower N utilization was associated with high abundance of bacteria that promote greater urinary N excretion through ruminal protein degradation.

本研究旨在表征不同氮保留效率 (ENR) 的牛肉的瘤胃细菌多样性。八头阉割公牛并装有瘤胃硅胶和十二指肠 T 型插管，用于交叉设计，连续三个时期和三个饮食。在每个实验期间，测量氮平衡，并根据氮利用效率数据，将阉牛分为三个 ENR 组：高（HNR，56.6% ± 3.3%，n  = 10），中（MNR，45.8% ± 2.2％，ñ  = 6），和低（LNR，37.7％±1.9％，ñ 在R.使用NbClust包2.0.4版= 8）Prevotellaceae，乳杆菌科，Leuconostocaceae，Clostridiales_Incertae_Sedis_XIII，毛螺，和 与 HNR 或 MNR 相比，消化链球菌科在 LNR 中的含量更高（P < 0.05）。发现 N 保留与Mogibacterium、Anaerofustis、Butyrivibrio、Coprococcus、Hespellia、Lactonifactor和Lachnospiraceae之间呈负相关（r ≤ -0.61；P  ≤ 0.05）。Prevotella、Hespellia、Lactonifactor、Lachnospiraceae_other和Anaerobiospirillum与尿N排泄呈正相关（r  >0.55；P  <0.01），与Elusimicrobia、Victivallis和Treponema呈负相关（r  < -0.41；P  < 0.05)。N使用保留组之间瘤胃细菌群落的调整显着不同。肉牛的高氮保留与瘤胃中较少的细菌有关；然而，需要在未来的研究中阐明固氮能力和未表征的瘤胃微生物。相比之下，较低的氮利用率与高丰度的细菌有关，这些细菌通过瘤胃蛋白质降解促进更多的尿氮排泄。