Omontese Bobwealth O, Sharma Ashok K, Davison Samuel, Jacobson Emily, DiConstanzo Alfredo, Webb Megan J, Gomez Andres
Department of Animal Science, University of Minnesota, Saint Paul, MN, 55108, USA.
Department of Food and Animal Sciences, Alabama A&M University, Normal, AL, 35762, USA.
Anim Microbiome. 2022 Mar 28;4(1):25. doi: 10.1186/s42523-022-00175-y.
Backgrounding (BKG), the stage between weaning and finishing, significantly impacts feedlot performance in beef cattle; however, the contributions of the rumen microbiome to this growth stage remain unexplored. A longitudinal study was designed to assess how BKG affects rumen bacterial communities and average daily gain (ADG) in beef cattle. At weaning, 38 calves were randomly assigned to three BKG systems for 55 days (d): a high roughage diet within a dry lot (DL, n = 13); annual cover crop within a strip plot (CC, n = 13); and perennial pasture vegetation within rotational paddocks (PP, n = 12), as before weaning. After BKG, all calves were placed in a feedlot for 142 d and finished with a high energy ration. Calves were weighed periodically from weaning to finishing to determine ADG. Rumen bacterial communities were profiled by collecting fluid samples via oral probe and sequencing the V4 region of the 16S rRNA bacterial gene, at weaning, during BKG and finishing.
Rumen bacterial communities diverged drastically among calves once they were placed in each BKG system, including sharp decreases in alpha diversity for CC and DL calves only (P < 0.001). During BKG, DL calves showed a substantial increase of Proteobacteria (Succinivibrionaceae family) (P < 0.001), which also corresponded with greater ADG (P < 0.05). At the finishing stage, Proteobacteria bloomed for all calves, with no previous alpha or beta diversity differences being retained between groups. However, at finishing, PP calves showed a compensatory ADG, particularly greater than that in calves coming from DL BKG (P = 0.02). Microbiome network traits such as lower average shortest path length, and increased neighbor connectivity, degree, number and strength of bacterial interactions between rumen bacteria better predicted ADG during BKG and finishing than variation in specific taxonomic profiles.
Bacterial co-abundance interactions, as measured by network theory approaches, better predicted growth performance in beef cattle during BKG and finishing, than the abundance of specific taxa. These findings underscore the importance of early post weaning stages as potential targets for feeding interventions that can enhance metabolic interactions between rumen bacteria, to increase productive performance in beef cattle.
育肥前期（BKG）是断奶至育肥结束之间的阶段，对肉牛的育肥场性能有重大影响；然而，瘤胃微生物群对这一生长阶段的作用仍未得到探索。一项纵向研究旨在评估BKG如何影响肉牛的瘤胃细菌群落和平均日增重（ADG）。断奶时，38头犊牛被随机分配到三种BKG系统中，为期55天（d）：干栏内的高粗饲料日粮（DL，n = 13）；带状小区内的一年生覆盖作物（CC，n = 13）；以及轮牧围场内的多年生牧草植被（PP，n = 12），断奶前的饲养方式相同。BKG期结束后，所有犊牛被转移至育肥场，为期142天，并以高能日粮育肥至出栏。从断奶到育肥结束期间定期对犊牛称重以确定ADG。在断奶、BKG期和育肥结束时，通过口腔探针采集液体样本并对16S rRNA细菌基因的V4区域进行测序，以分析瘤胃细菌群落。
犊牛一旦被置于每种BKG系统中，其瘤胃细菌群落就会出现显著差异，仅CC和DL犊牛的α多样性显著降低（P < 0.001）。在BKG期，DL犊牛的变形菌门（琥珀酸弧菌科）大幅增加（P < 0.001），这也与更高的ADG相对应（P < 0.05）。在育肥阶段，所有犊牛的变形菌门都大量增殖，之前各组之间的α或β多样性差异均未保留。然而，在育肥结束时，PP犊牛表现出补偿性ADG，尤其高于来自DL BKG的犊牛（P = 0.02）。与特定分类学特征的变化相比，瘤胃细菌之间较低的平均最短路径长度、增加的邻居连通性、度、细菌相互作用的数量和强度等微生物群网络特征，能更好地预测BKG期和育肥结束时的ADG。
通过网络理论方法测量的细菌共丰度相互作用，比特定分类群的丰度能更好地预测肉牛在BKG期和育肥结束时的生长性能。这些发现强调了断奶后早期阶段作为饲养干预潜在目标的重要性，这种干预可以增强瘤胃细菌之间的代谢相互作用，从而提高肉牛的生产性能。
