Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA, United States of America.
PLoS One. 2024 Sep 20;19(9):e0310648. doi: 10.1371/journal.pone.0310648. eCollection 2024.
Ruminant livestock are major contributors to anthropogenic methane emissions in the United States and worldwide. Enteric methane is generated by methanogenic archaea residing in ruminant digestive tracts. Information on when methanogens colonize the gut and when they begin to interact with bacteria during the early phases of the ruminant life cycle is less explored. The objectives of this study were (i) to investigate the composition of the methanogenic archaeal community at birth and through the weaning transition and (ii) to determine if and when the methanogenic archaea begin to interact with bacteria in the lower gut of neonatal dairy calves. Ten female Holstein calves (approximately 45kg birth weight) were enrolled in the study. Fecal samples were collected every two weeks (Wk 2, 4, 6, 8, 10, and 12) between birth and weaning and analyzed for methanogenic archaeal diversity via 16S rRNA amplicon sequencing and quantitative real-time PCR (RT-qPCR). Estimates of alpha diversity (Observed species, and Shannon diversity index) and beta diversity (weighted and unweighted UniFrac distances) showed significant differences (P < 0.05) between archaeal communities across timepoints. Both 16S rRNA amplicon sequencing and RT-qPCR analyses revealed Methanobrevibacter was the most prevalent genus at Wk2, Wk4, and Wk6, whereas Methanosphaera gradually increased with time and was most abundant at Wk10 and Wk12. Correlation analysis revealed that Methanobrevibacter and Methanosphaera were inversely correlated with each other and formed distinct cohorts with specific bacterial lineages similar to those reported in the mature rumen, thus revealing that these associations are established during the preweaning period. Therefore, the preweaning period presents a window of opportunity to interfere with early-life methanogenic colonization with the ultimate goal of reducing enteric methane emissions without perturbing ruminal function later in the life of dairy cattle.
反刍动物是美国和全球人为甲烷排放的主要贡献者。瘤胃甲烷是由栖息在反刍动物消化道中的产甲烷古菌产生的。关于产甲烷菌何时定植于肠道以及它们在反刍动物生命周期的早期阶段何时开始与细菌相互作用的信息，研究得较少。本研究的目的是：（i）研究产甲烷古菌群落的组成，包括出生时和断奶过渡期；（ii）确定产甲烷古菌是否以及何时开始与新生奶牛犊牛下肠道中的细菌相互作用。本研究纳入了 10 头雌性荷斯坦奶牛（出生体重约 45kg）。在出生到断奶期间，每两周（第 2、4、6、8、10 和 12 周）采集粪便样本，并通过 16S rRNA 扩增子测序和定量实时 PCR（RT-qPCR）分析产甲烷古菌的多样性。α多样性（观察到的物种和香农多样性指数）和β多样性（加权和非加权 UniFrac 距离）的估计值显示，不同时间点的古菌群落之间存在显著差异（P < 0.05）。16S rRNA 扩增子测序和 RT-qPCR 分析均表明，Methanobrevibacter 是第 2、4 和 6 周最普遍的属，而 Methanosphaera 随着时间的推移逐渐增加，在第 10 和 12 周时最为丰富。相关性分析表明，Methanobrevibacter 和 Methanosphaera 相互呈负相关，并且与特定细菌谱系形成独特的群集，与成熟瘤胃中报道的相似，这表明这些关联是在断奶前建立的。因此，断奶前是一个干预早期生命产甲烷定植的机会窗口，最终目标是在奶牛生命后期不干扰瘤胃功能的情况下减少肠道甲烷排放。
