Epimural Indicator Phylotypes of Transiently-Induced Subacute Ruminal Acidosis in Dairy Cattle

Abstract

The impact of a long-term subacute rumen acidosis (SARA) on the bovine epimural bacterial microbiome (BEBM) and its consequences for rumen health is poorly understood. This study aimed to investigate shifts in the BEBM during a long-term transient SARA model consisting of two concentrate-diet-induced SARA challenges separated by a 1-week challenge break. Eight cows were fed forage and varying concentrate amounts throughout the experiment. In total, 32 rumen papilla biopsies were taken for DNA isolation (4 sampling time points per cow: at the baseline before concentrate was fed, after the first SARA challenge, after the challenge break, and after the second SARA challenge). Ruminal pH was continuously monitored. The microbiome was determined using Illumina MiSeq sequencing of the 16S rRNA gene (V345 region). In total 1,215,618 sequences were obtained and clustered into 6833 operational taxonomic units (OTUs). Campylobacter and Kingella were the most abundant OTUs (16.5 and 7.1%). According to ruminal pH dynamics, the second challenge was more severe than the first challenge. Species diversity estimates and evenness increased during the challenge break compared to all other sampling time points (P < 0.05). During both SARA challenges, Kingella- and Azoarcus-OTUs decreased (0.5 and 0.4 fold-change) and a dominant Ruminobacter-OTU increased during the challenge break (18.9 fold-change; P < 0.05). qPCR confirmed SARA-related shifts. During the challenge break noticeably more OTUs increased compared to other sampling time points. Our results show that the BEBM re-establishes the baseline conditions slower after a SARA challenge than ruminal pH. Key phylotypes that were reduced during both challenges may help to establish a bacterial fingerprint to facilitate understanding effects of SARA conditions on the BEBM and their consequences for the ruminant host.

Epimural bacterial community structure in the rumen of Holstein cows with different responses to a long-term subacute ruminal acidosis diet challenge

“…Of the ruminal microbial communities, bacteria in the rumen fluid and those attached to feed particles have attracted considerable research interest, but comparatively less is known about bacteria attached to the rumen wall, commonly known as epimural bacteria. In recent years, a few studies have been published describing the bovine epimural bacterial microbiome (BEBM) using high-throughput sequencing methods (Mao et al, 2015;Liu et al, 2016;Wetzels et al, 2016), but each have shown low sequence similarity between detected phylotypes and best type strain hits. From the host perspective, the BEBM is the first contact between the rumen environment and the rumen epithelium, competing with adherent and putative pathogenic microorganisms (Kamra, 2005;Khafipour et al, 2011).…”

Intramammary infusion of Escherichia coli lipopolysaccharide negatively affects feed intake, chewing, and clinical variables, but some effects are stronger in cows experiencing subacute rumen acidosis

“…The severity and duration of SARA conditions are particularly relevant for rumen health (Khafipour et al, 2009;Schwaiger et al, 2013). Recent research of our team observed that intermittent SARA conditions are stronger than persistent SARA conditions, likely because the rumen and its microbiota have less chance to adapt and the VFA are less absorbed across the reticulorumen wall Qumar et al, 2016;Wetzels et al, 2016). The latter is a major concern, as VFA absorption is essential for the regulation of the intraruminal pH and the alleviation of SARA conditions (Aschenbach et al, 2011;Schwaiger et al, 2013).…”

Influence of the artificial sodium saccharin sweetener Sucram®on the microbial community composition in the rumen content and attached to the rumen epithelium in dairy cattle: A pilot study

“…Two OTUs (6 and 34) with reduced abundance found in samples supplemented with Sucram ® were classified as potential sulfate-reducing bacteria (SRB) within the Desulfobulbus genus and were related to Desulfobulbus oligotrophicus (sequence similarity >97% using NCBI BLAST [46, 47]. SRB are commonly found within the gastrointestinal tract of ruminants [48] and particularly at the rumen wall [44, 49] and are known to reduce SO 3 2− to SO 4 2− and H 2 S [50]. This leads to the reduction of available metabolic hydrogen generated in cellulose and SCFA metabolism [47, 51].…”